"The literature on this area of ​​research is remarkable and confusing for the non-specialist. This volume edited by Roy Gross and Dagmar Beier is a clear landmark. A top-class science, international team of authors presents in 18 chapters the latest developments in the field of two-component regulatory systems, from genetics through the biochemistry and cell biology to structural biology. I have read with great profit the excellently written and carefully edited contributions. I recommend this book to every student and senior scientist who is interested in approaches to signal transduction processes in microorganisms. The editors and authors have presented the current state of research on a complex topic coherently and for a wide audience." from Erhard Bremer (Marburg, Germany) writing in Biospectrum (2013) 19: 224. read more ...

Two-Component Systems in Bacteria Edited by: Roy Gross and Dagmar Beier ISBN: 978-1-908230-08-9 Publisher: Caister Academic Press Publication Date: August 2012 Cover: hardback "I recommend this book to every student and senior scientist" (Biospektrum)

"well-written and informative chapters on stress systems ... on high scientific level and with extensive references ... chapters of this book are worth reading" from Erhard Bremer (Marburg, Germany) writing in Biospektrum (2013) 19: 107-111 read more ...

Stress Response in Microbiology Edited by: Jose M. Requena ISBN: 978-1-908230-04-1 Publisher: Caister Academic Press Publication Date: June 2012 Cover: hardback "well-written and informative" (Biospektrum)

"... well-written reviews by highly regarded researchers, starting with how TCSs are classified and organised, and current understanding of structural knowledge, and moving on to novel aspects of signal transduction mechanisms, TCS function and gene regulation ... This book is an excellent choice for graduate-level education and researchers in the field and would be a useful addition to any research group, department or university library in a research-active institution or pharmaceutical company." from Mary Phillips-Jones (University of Central Lancashire, UK) writing in Microbiology Today (2013) read more ...

Two-Component Systems in Bacteria Edited by: Roy Gross and Dagmar Beier ISBN: 978-1-908230-08-9 Publisher: Caister Academic Press Publication Date: August 2012 Cover: hardback "a useful addition to any research group" (Microbiol. Today)

from Hendrik Szurmant writing in Two-Component Systems in Bacteria:

The YycF/YycG two-component signal transduction system has become an enigma since its initial discovery as the only signal transduction system essential for viability in Bacillus subtilis, Staphylococcus aureus and Streptococcus pneumoniae. Conserved across the low G+C Gram-positives, over a decade worth of dedicated molecular investigations have identified some of the factors that control the YycG kinase activity and the genes that are regulated by the YycF transcription factor. A picture has emerged where the YycFG system is embedded in the physiology of the cell and serves to coordinate essential physiological processes such as cell wall homeostasis and cell division. Several regulatory connections with other signaling systems have been recognized. The YycFG system has surfaced as an important player in the acquisition of antibiotic resistances in clinical isolates of significant human pathogens and has become the target of dedicated antimicrobial drug screening efforts. This review summarizes the current state of knowledge on this and other essential two-component signaling systems in Gram-positive bacteria.

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from writing in Two-Component Systems in Bacteria:

Further reading: Two-Component Systems in Bacteria

from Dagmar Beier writing in Two-Component Systems in Bacteria:

In a classical two-component system a response regulator is activated via phosphoryl group transfer from a cognate histidine kinase in order to elicit a cellular output response to a specific stimulus. However, it is increasingly recognized that response regulator proteins do not necessarily rely on this standard activation mode. The so-called orphan response regulators lack a cognate histidine kinase as phosphorylation partner. In many cases these proteins retain their function upon substitution of the phosphate-accepting aspartic acid residue in the receiver domain suggesting phosphorylation-independent mechanisms for output response control. The concept of unorthodox signaling to and activation of a response regulator is supported by the occurrence of atypical response regulators in several bacteria. Atypical response regulators comprise degenerate receiver domains with conserved residues required for the phosphotransfer reaction and signal propagation within the response regulator protein being absent, which certainly precludes canonical receiver phosphorylation. Nevertheless, atypical response regulators are involved in various cellular functions including vegetative cell growth, differentiation, secondary metabolism and virulence.

Further reading: Two-Component Systems in Bacteria

"brings together 17 expert groups to review aspects of the stress response in bacteria, mycoplasmas, yeast and a range of protozoans. Chapters are of reasonable size, well (and currently) referenced and show a common style, which is a mark of good editing ... well and sensibly illustrated ... will be of interests to bacteriologists, parasitologists and the growing number of scientists interested in the cell stress response." from Brian Henderson (University College London, UK) writing in Microbiology Today (2012) read more ...

Stress Response in Microbiology Edited by: Jose M. Requena ISBN: 978-1-908230-04-1 Publisher: Caister Academic Press Publication Date: June 2012 Cover: hardback "well and sensibly illustrated" (Micro. Today)

from David E. Whitworth writing in Two-Component Systems in Bacteria:

Two-component systems (TCSs) are common signal transduction pathways found abundantly in most phyla except animals. The basic TCS pathway involves two multi-domain proteins. The first is a histidine protein kinase (HPK) whose autokinase activity is dependent upon an environmental stimulus. The second is a response regulator (RR), onto which a phosphoryl group is transferred from the phosphorylated HPK, and which mediates phosphorylation-dependent effects within the cell. TCS proteins can be readily identified from genomic sequences, however, approaches for identifying and classifying TCS proteins are non-trivial because TCSs are multi-domain, multi-gene pathways, which exhibit considerable heterogeneity in their gene and domain organisation. This review provides an overview of the domain architectures and genetic organisation of TCSs, including the common TCS variants known as phosphorelays and chemosensory systems. Strategies for the identification of TCS genes are described, alongside systems for categorising TCS proteins that exploit the evolutionary relationships between TCS proteins to provide biologically relevant insights. The development of such classification systems are reviewed in addition to the current state of the art, to help the reader navigate through the extensive literature on this topic.

Further reading: Two-Component Systems in Bacteria

from Paphavee Lertsethtakarn, Jenny Draper and Karen M. Ottemann writing in Two-Component Systems in Bacteria:

The gastric pathogenic bacterium Helicobacter pylori has a relatively simple chemotaxis system, with four chemoreceptors plus a set of signal transduction proteins consisting of the CheA kinase, CheW and CheV coupling proteins, a CheY response regulator, the CheZ phosphatase and an unusual protein termed ChePep. H. pylori chemotaxis response has proved challenging to study, but studies have established that H. pylori uses its chemotaxis system to move away from low pH and autoinducer-2, and to respond to cellular energy status along with several chemicals . During stomach infection, H. pylori chemotaxis plays multiple roles including promoting early infection and critical epithelial interactions that drive a wild-type immune response.

Further reading: Two-Component Systems in Bacteria

from Stephen C. Smith, Juan-Jesus Vicente and Kathleen R. Ryan writing in Two-Component Systems in Bacteria:

The intricate cell division and developmental cycle of the α-Proteobacterium Caulobacter crescentus has been studied for four decades. During that time, elegant genetic screens and comprehensive post-genomic methods have uncovered a branched network of two-component signaling proteins that orchestrates Caulobacter cell cycle progression and morphological development. In addition to yielding the first and most detailed picture of bacterial cell cycle control, Caulobacter studies have revealed novel ways in which two-component proteins generate cellular outputs, interact with each other, and are themselves regulated.

Further reading: Two-Component Systems in Bacteria

from Françoise Jacob-Dubuisson, René Wintjens, Julien Herrou, Elian Dupré and Rudy Antoine writing in Two-Component Systems in Bacteria:

The whooping cough agent Bordetella pertussis regulates the expression of its virulence regulon through the two-component system BvgAS. BvgA is a canonical response regulator serving as a transcriptional activator when phosphorylated. BvgS is a multidomain, hybrid sensor-kinase harbouring several cytoplasmic domains that mediate a complex phospho-transfer cascade. BvgS also contains two periplasmic Venus flytrap (VFT) domains in tandem. It is thus the prototype for a large family of bacterial VFT-containing sensor-kinases, whose molecular mechanisms for signal perception and transduction remain to be deciphered. Ubiquitous in nature, VFT domains usually function along a clamshell model, with two lobes that enclose specific ligands. Structure/function analyses of the second VFT domain of BvgS have indicated a non-canonical behaviour, whereby this domain adopts a closed conformation that gives a positive signal to the system in the absence of a bona fide ligand and can also bind negative signals that turn off the system. Sequence analyses of BvgS have shown a strong conservation of the region linking the periplasmic and cytoplasmic domains, indicating that it is essential for signal transduction. On the contrary, the linkers between VFT domains are not conserved, and thus the VFT most likely communicate with each other via their interfaces.

Further reading: Two-Component Systems in Bacteria

from David A. Jacques, J. Mitchell Guss and Jill Trewhella writing in Two-Component Systems in Bacteria:

Antikinases are protein inhibitors of the bacterial sensor histidine kinases found in two-component systems. Antikinases act by binding the highly-conserved autokinase domains and thereby inhibit autophosphorylation. Antikinases offer unique opportunities to understand histidine kinase function and inhibition, and as histidine kinases are not found in mammals, knowledge of their structures and binding can potentially be exploited for the development of novel antimicrobial compounds. This review describes our current understanding of the three known antikinases: Sda and KipI from Bacillus subtilis and FixT from Sinorhizobium meliloti, with a focus on understanding of their detailed structures and mechanisms of action.

Further reading: Two-Component Systems in Bacteria

from Ralf Heermann and Kirsten Jung writing in Two-Component Systems in Bacteria:

The KdpD/KdpE system is one of the most distributed histidine kinase/response regulator systems in bacteria. This two-component system controls expression of the kdpFABC operon encoding the high affinity K⁺ uptake system KdpFABC. KdpD/KdpE is activated whenever the constitutively expressed K⁺ uptake systems are unable to keep up with the cellular need for K⁺. Typical KdpD/KdpE activating conditions comprise K⁺ limitation or osmotic stress. The histidine kinase KdpD is composed of several subdomains that are important for stimulus perception, modulation of the kinase to phosphatase ratio, and signaling. The response regulator KdpE receives the phosphoryl group from KdpD and induces kdpFABC transcription. The three-dimensional structure of the KdpE receiver domain gives insights into the activation mechanism of this transcriptional regulator. Two accessory proteins, the universal stress protein UspC and the phosphotransferase system component IIA^Ntr, interact with KdpD, whereby kdpFABC expression is modulated under certain physiological conditions. Here we will review the nature of the stimulus of KdpD/KdpE in correlation with structural features as well as the interconnectivity of KdpD/KdpE with K⁺ supply, osmotic stress response and virulence.

Further reading: Two-Component Systems in Bacteria

from Julien Brillard and Véronique Broussolle writing in Stress Response in Microbiology:

Among the soil bacteria of the spore former genus Bacillus, the human pathogens mostly belong to the B. cereus group. This species is divided in seven phylogenetic groups, with particular traits in virulence, and particular growth temperature ranges, where each of these seven phylogenetic groups corresponds to a specific "thermotype", showing clear differences in ability to grow at low or high temperatures. After a temperature downshift, changes that occur in the bacterial cell include a decrease of the membrane fluidity, a stabilisation of secondary structures of nucleic acids which consequently causes a decreased efficiency in transcription and translation, a misfolding of some proteins, etc. The bacterial cell response involves various mechanisms which, among the Bacillus genus, have been mostly studied in Bacillus subtilis. This chapter focuses on current research about B. cereus low-temperature adaptation, compared to what is well described in B. subtilis.

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from Yoko Eguchi, Eiji Ishii and Ryutaro Utsumi writing in Two-Component Systems in Bacteria:

Two-component system (TCS) connectors are proteins that connect different TCSs. By connecting TCSs, they integrate the signals to which each TCS responds, and enable the cell to respond flexibly to the fluctuating environment. A number of auxiliary proteins of TCSs, which bind to the components of TCSs for modification, have been reported. When the expression of such TCS auxiliary proteins is controlled by a TCS, it connects the two TCSs and is termed a TCS connector. Several TCS connectors have been identified in Salmonella and Escherichia coli. In this chapter, we describe how these TCS connectors and the TCSs they connect form a signal transduction network. TCS connectors in Bacillus subtilis as well as TCS auxiliary proteins as candidates of TCS connectors are also introduced. We have clarified a small portion of the predicted two-component signal transduction network as an initial description of the complicated signal network that exists in bacteria.

Further reading: Two-Component Systems in Bacteria

from Isabel Delany and Kate L. Seib writing in Stress Response in Microbiology:

Mechanisms to sense, avoid and scavenge oxidants as well as repair damaged biomolecules are important survival and virulence factors of the obligate human pathogens Neisseria meningitidis and Neisseria gonorrhoeae. These bacteria are routinely exposed to several forms of oxidative and nitrosative stress during colonisation and interaction with the host, of which superoxide, hydrogen peroxide and nitric oxide are some of the key oxidants that result in damage to the bacteria. However, the pathogenic Neisseria express an array of defense mechanisms to combat oxidative and nitrosative stress, such as catalase, superoxide dismutase, nitric oxide reductase, as well as thiol-based defenses and proteins involved in metal homeostasis and repair of damage to DNA and proteins. The expression of these defenses is tightly regulated by a series of transcription factors containing redox-sensitive active sites, including OxyR, Fur, PerR/Zur, FNR, MseR, LexA NsrR, NmlR, which sense and maintain the redox homeostasis of the cell.

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from Alexander J. Ninfa writing in Two-Component Systems in Bacteria:

Many of the two-component system transmitter proteins bring about both the phosphorylation and dephosphorylation of their cognate receiver proteins. While the mechanism of the transmitter protein kinase activity was relatively easy to discern biochemically, investigation of the phosphatase activity has proven more difficult owing to the involvement of widely dispersed portions of the transmitter protein in the activity and the corresponding requirement to study the activity using intact, full-length transmitter proteins. Here, I review the genetics, physiology, and biochemistry of the transmitter protein phosphatase activity, with special emphasis on possible mechanisms of receiver protein dephosphorylation, relationship of the transmitter phosphatase activity to the autophosphatase activity of the receiver protein, and physiological significance of the activity.

Further reading: Two-Component Systems in Bacteria

Stress Response in Microbiology comprises 17 excellent chapters, each one dedicated to a particular microorganism or group of microorganisms; most of the selected organisms represent important health threats for humans. With its coverage of a broad range of model organisms, the book gives a complete overview of the stress response in both prokaryotic and eukaryotic microorganisms, providing detailed information for researchers, as well as for teachers and students in the fields of microbiology and parasitology. The chapter authors, among the best in their respective fields, have done an excellent job of synthesizing data from numerous studies and making the book a well-referenced work. Thus, we hope that this work will serve as an informative resource for researchers and students at all levels.

The first chapter provides a complete description of the cell envelope stress responses and the stress-sensing regulatory systems, mainly in Gram-negative bacteria. Chapter 2 gives an overview on the stress responses in several pathogenic species of the genus Streptococcus; acid, oxidative and nutritional stresses are presented here in depth. Chapter 3 is devoted to oxidative and nitrosative defenses in pathogenic Neisseria species. In addition, the authors have included detailed information about biologically relevant oxidants and the chemical reactions involving oxidants in biological systems that are of considerable basic scientific interest. The relationship between stress response and virulence in the food-borne pathogen Listeria monocytogenes is the main focus of Chapter 4. Chapter 5 focuses on current knowledge and research activity about low-temperature adaptation of the spore former and human pathogen Bacillus cereus. Chapter 6 gives a complete overview of the main stress response mechanisms employed by Salmonella for survival in nutrient-limited conditions and during osmotic and acid stress exposure. In the next chapter, devoted to Yersinia, the authors review the responses of this pathogen to heat and cold shocks, encounter with macrophages and macrophage-like conditions. Also, the extracytoplasmic stress responses are covered in detail in Chapter 7. Chapter 8 describes how the stress response systems are vitally important for the vibrios to successfully establish in the host. Chapter 9 describes the function of the major stress proteins within mycobacteria, paying special attention to the interaction between the bacterial heat shock proteins and the host's cellmediated immune response. Chapter 10 focuses on the types of stresses that mycoplasmas encounter in vivo, such as heat shock, oxidative stress, osmolarity shifts, hormone exposure, iron deprivation and biofilm formation. In Chapter 11, the authors describe the different mechanisms used by model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, as well as the pathogenic fungus Candida albicans, to sense and transduce stress signals to stressactivated protein kinases pathways in response to osmotic, heat and oxidative stresses. Among eukaryotic microorganisms, one group that is subjected to dramatic environmental changes throughout their complex life cycle are the parasitic protozoa, which are the focus of the remaining chapters. Chapter 12 summarizes the current knowledge about the responses of the malaria parasite Plasmodium falciparum to a variety of stresses: drug treatments, changes in temperature and elevation of oxidative stress. Chapter 13 summarizes the recent findings on the Toxoplasma gondii stress responses and the implication of these processes in the biology and pathogenesis of this parasite. The focus of Chapter 14 is the stress response in Leishmania, containing a comprehensive view on the implications of the stress response in parasite survival, in cytodifferentiation and in apoptotic processes. Chapter 15 reviews the components of the Trypanosoma cruzi stress response with emphasis on its relevance to the parasite biology and to Chagas' disease transmission, pathogenesis and treatment. In Chapter 16, the authors have compiled the most significant molecular and biological aspects related to the mechanisms and components of the stress response of T. brucei to adapt and survive in the bloodstream of mammals. The final chapter, devoted to Entamoeba histolytica, gives special emphasis to the oxidative and nitrosative stresses experienced by this protozoan parasite.

Jose M. Requena

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from Jiang Wu, Vladimira Dragnea and Carl Bauer writing in Two-Component Systems in Bacteria:

Sensor kinases that respond to changes in redox have been described in several bacterial systems. This review is centered on the molecular mechanism of redox sensing in a select group of sensor kinases that have been well-defined biochemically. We cover the role of oxidized ubiquinone and redox active cysteine in controlling the kinase activity of the sensor kinases RegB and ArcB of Rhodobacter capsulatus and Escherichia coli, respectively. We also review inhibition of kinase activity that occurs upon the binding of dioxygen to heme to a PAS domain in FixL of rhizobia and upon the binding of dioxygen to heme to a GAF domain in DosT of Mycobacterium tuberculosis. Finally, we discuss recent evidence that the photoreceptor LovK of Caulobacter crescentus contains a redox active flavin that when reduced inhibits the ability of LovK to undergo a photocycle that regulates kinase activity.

Further reading: Two-Component Systems in Bacteria

from Alfonso Olivos-García, Emma Saavedra, Erika Rubí Luis-García, Mario Nequiz and Ruy Pérez-Tamayo writing in Stress Response in Microbiology:

Several species belonging to the genus Entamoeba can colonize the mouth or the human gut; only Entamoeba histolytica, however, is pathogenic to the host, causing the disease amebiasis. This illness is responsible for one hundred thousand human deaths per year worldwide, affecting mainly underdeveloped countries. Throughout its entire life cycle, or invasion of human tissues, the parasite is constantly subjected to stress conditions. Under in vitro culture, this microaerophilic parasite can tolerate up to 5% oxygen concentrations; however, during tissue invasion the parasite has to cope with the higher oxygen content found in well perfused tissues (4-14%) and with reactive oxygen and nitrogen species (ROS and NOS, respectively) derived from both host and parasite. In almost all living cells, a low-dose, tightly regulated generation of ROS and NOS mediates several physiological functions such as growth, differentiation and metabolism; an excess of ROS and NOS, however, damages DNA, proteins and lipids, leading to cell death. In this chapter we review the latest findings regarding the physiological and pathological molecular functions of oxidative and nitrosative stresses in E. histolytica and discuss whether the molecules involved in the antioxidant system of the parasite can be appropriate drug targets for the treatment of amebiasis.

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from Ewa WaŁecka and Jacek Bania writing in Stress Response in Microbiology:

L. monocytogenes is a food-borne pathogen widespread in the environment. The majority of human listeriosis is associated with consumption of contaminated food. It has the ability to invade many types of nonphagocytic cells and spread from cell to cell, crossing important barriers in host organism. Despite intensified surveillance in food manufacturing serious cases of listeriosis are still reported. Before L. monocytogenes causes disease it has to endure adverse conditions encountered in food during its processing and storage, such as supraoptimal temperatures, low pH, high osmolarity, presence of oxidants. In the human intestinal tract L. monocytogenes must overcome another set of challenges as the low pH of the stomach, volatile fatty acids, low oxygen levels, osmotic stress, nutrient variability, bile stress and natural flora in the intestine. To survive in hostile environment bacteria adjust their metabolism which involves expression of stress response genes. Consequently, bacteria synthesize proteins that repair damages, maintain the cell stability, eliminate the stress factor, and restore homeostasis. The stress response not only affects L. monocytogenes resistance to subsequent doses of stress factors, but can also alter the pathogen's virulence.

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from Melissa L. Madsen and F. Chris Minion writing in Stress Response in Microbiology:

Because mycoplasmas lack cell walls and have a limited genome capacity, there has been interest in their regulation of gene expression in these unique organisms. Their restriction to the host environment only adds to the intrigue. That environment, however, is not constant, changing with the host adaption to colonization and disease by the mycoplasma. This review focuses on the types of stresses the mycoplasma might encounter in vivo including heat shock, oxidative stress, osmolarity shifts, hormone exposure, and iron deprivation. Biofilm studies are included because of their use by other pathogens as a defense measure to resist killing in the host. The field of mycoplasmology is still in its infancy, particularly in regards to gene regulatory mechanisms. There have even been suggestions that mycoplasmas may not have the capacity to respond to changing environmental conditions. The studies reported here, however, show unequivocally that mycoplasmas do respond to their environment by altering transcription rates. How that is accomplished is still unknown except in one instance, heat shock. In summary, like all bacteria, mycoplasmas respond to their environment. That response may be limited, but it appears essential to their survival.

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from Sylke Müller and Christian Doerig writing in Stress Response in Microbiology:

The life cycle of malaria parasites comprises a complex succession of developmental stages occurring in two different hosts, the human patient and the mosquito vector. In both hosts, the parasite encounters hostile environments and must deal with stresses such as immune responses, sharp temperature shifts and exposure to drugs; partly because of large-scale haemoglobin degradation in the infected erythrocyte and resulting haeme release, oxidative stress is another challenge that the parasite must face. In contrast to other eukaryotes where stress response is largely mediated through a well-defined and robust transcriptional response, it appears that malaria parasites opted for a different strategy. In line with the largely fixed transcriptional programme that characterises the progression of the organisms through their life cycle stages, the transcriptional response to several stresses (such as drug treatments) consists primarily of low-amplitude, genome-wide changes of transcript abundance. However, recent findings suggest that specific transcriptome adaptations, that affect selected aspects of the parasites' physiology, also occur. Overall, the absence in the parasite's kinome of classical stress response mediators such as SAPKs/JNKs, together with the relative scarcity in transcription factors, suggest a low level of flexibility of the parasite in implementing classical eukaryotic stress response pathways. Post-transcriptional mechanisms are expected to play crucial roles in stress response in Plasmodium as exemplified by the demonstrated involvement of an eIF2alpha kinases in response to starvation stress.

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from Marcelo A. Comini, Andrea Medeiros and Bruno Manta writing in Stress Response in Microbiology:

African trypanosomes (Trypanosoma brucei sp.) are unicellular eukaryotic organisms that undergo a complex life cycle shuttling between an invertebrate (vector) and a mammalian host. The parasites have evolved sophisticated and efficient mechanisms to cope with, and adapt to, different environmental conditions. Distinct physical (temperature, pH, osmotic pressure) and biological (endo- and exo-biotic molecules, antibodies, proteases, etc) stimuli acting individually or in a concerted manner induce an adaptive response in the parasite. Depending on the nature and extent of the stress, the cellular response can be transient or long-term and associated with minor or major morphological and metabolic changes. In this chapter we compile the most significant molecular and biological aspects related to the mechanisms and components of the stress response of T. brucei to adapt and survive in the bloodstream of mammals.

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from N. Kaye Horstman and Andrew J. Darwin writing in Stress Response in Microbiology:

Pathogenic Yersinia species have long been studied as important causes of human disease and as model organisms to understand widely conserved mechanisms of bacterial virulence. Like all bacteria, these pathogens must respond to a variety of potentially damaging conditions to ensure their survival. This chapter begins by introducing the pathogenic Yersinia and the aspects of their lifestyles that are likely to require successful response to stress. The emphasis is primarily on conditions relevant to pathogenesis. Then, some genome-wide transcription and gene function studies that have identified or implicated stress response mechanisms are summarized. Next, more focused analyses of response to increased and decreased temperature, encounter with macrophages, and macrophage-like conditions are covered in more detail. Finally, the so-called extracytoplasmic stress responses (ESRs) that are activated by changes to the cell envelope will be described. Several of these ESRs have been directly associated with the infectious process in Yersinia. Inactivation of one, the phage-shock-protein (Psp) system, completely attenuates Y. enterocolitica. As a result, the Psp system has become the most extensively studied Yersinia stress response. Therefore, the final section specifically describes the regulation and function of this critical stress response system.

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from Richard W. Stokes writing in Stress Response in Microbiology:

There are many species of mycobacteria, some of which are pathogens of man. Mycobacterium tuberculosis, the etiological agent of tuberculosis, is a major pathogen of man with about one third of the world's population being infected. It resides within host macrophages where it can survive in a dormant state for the lifetime of the host with about 10% of all infections resulting in disease. This environment results in the bacteria being exposed to numerous stresses including nutrient deprivation, reduced oxygen availability, exposure to pH changes and exposure to the antimicrobial activities of the host's cell-mediated immune response. The bacterium responds with its own defense mechanisms that include the increased expression of stress proteins (also called heat shock proteins). This review describes the regulation and function of the major stress proteins within mycobacteria such as the GroEL, GroES and DnaK homologues along with hspX (alpha-crystallin) and others. The multiple copies of cpn60 (GroEL homologue) that are found within mycobacteria are discussed along with their putative roles as chaperonins but also as "moonlighting" proteins with roles in immunomodulation and receptor/ligand interactions that facilitate the pathogenesis of M. tuberculosis.

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from Suzanne Humphrey, Tom J. Humphrey and Mark A. Jepson writing in Stress Response in Microbiology:

Salmonella enterica are the causative agents of a spectrum of diseases, including enteric fever and self-limiting gastroenteritis and remain significant foodborne pathogens throughout both the developed and developing worlds. The ability to actively invade and reside within gut epithelia and macrophages is an important process in the establishment of Salmonella infection, generating localised inflammatory responses and facilitating systemic spread of the pathogen within the host. Many environments, including food matrices, the external environment and conditions within the host, present a range of stressful challenges that Salmonella must overcome in order to survive and establish infection. Salmonella utilise a diverse range of stress response strategies, including expression of alternative RNA polymerase sigma factors, uptake of compatible solutes, increased expression of genes encoding uptake or efflux pumps, and production of proteins with roles in protecting and repairing stress-induced damage, in order to facilitate their survival in suboptimal and stressful growth environments. Additionally, the ability of Salmonella to undergo morphological changes during stress exposure and rapidly recover from stress conditions commonly encountered within food matrices represents a pertinent issue for food processing and public health.

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from Jacqueline Abranches and Josá A. Lemos writing in Stress Response in Microbiology:

The genus Streptococcus is comprised of a diverse group of organisms, which includes food-associated, commensal and pathogenic species. The importance of this genus to the food industry and the capacity of certain species to infect animals and humans make streptococci one of the best-studied Gram-positive bacteria. In this chapter, we will describe the stress responses of the four major pathogenic streptococcal species: Streptococcus mutans, the etiologic agent of dental caries, S. pyogenes (commonly known as Group A Streptococcus or GAS), responsible for a variety of suppurative disesases as well as life-threatening invasive infections and post-infection sequelae, S. agalactiae (Group B Streptococcus or GBS), a major bacterial pathogen associated with neonatal infections, and S. pneumoniae, the leading causative agent of bacterial pneumoniae. In the following pages, the description of the stress response mechanisms for each individual species is presented in the context of the environmental stress condition. In addition to highlighting the cross-species conservation of certain stress reponses, this organization will allow the reader to follow the progresses obtained in each species, and, at the same time, identify areas that have been poorly explored.

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from Eulàlia de Nadal and Francesc Posas writing in Stress Response in Microbiology:

Adaptation to environmental stress requires changes in many aspects of cellular physiology essential for cell survival, such as gene expression, translation, metabolism, morphogenesis or cell cycle progression. Accordingly, the ability of eukaryotic cells to survive and thrive within adverse environments depends on rapid and robust stress responses. Stress-activated protein kinases (SAPKs) pathways are key elements on intracellular stress-signalling networks to respond and adapt to extracellular changes. In this review, we describe the different mechanisms used by model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, as well as the pathogenic fungus Candida albicans, to sense and transduce stress signals to SAPKs in response to osmo, heat and oxidative stresses. Moreover, other signalling pathways related to stress are discussed. Although much remains to be learned, studies from yeast have served to understand how stress signalling molecules adjust precise and efficient adaptation strategies to maximize cell survival in response to extracellular stimuli.

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from Patricia Casino, Marisa López-Redondo and Alberto Marina writing in Two-Component Systems in Bacteria:

Two-component systems (TCSs) constitute a signal transduction mechanism, mainly found in prokaryotes, which is relatively simple as they are basically formed by two proteins: a histidine kinase (HK) and a response regulator (RR). These two proteins are able to transmit all kinds of signals productively and elegantly by the use of phosphorelays in order to ensure cell survival. For this purpose, the HK possesses many qualities; first it is able to sense a signal, second it binds ATP, and third it autophosphorylates on a catalytic His residue. Subsequently, the RR comes into play to promote the final response, but first it needs to be phosphorylated on a catalytic Asp residue via a phosphoryl group transfer from the phosphorylated His of the HK. The phosphorylated RR (RR~P) can thus elicit many diverse responses, which generally involve binding to DNA to activate specific genes. Finally, the system is shut down by the dephosphorylation of the RR~P, a mechanism which can be performed by the RR itself, or assisted by the HK. Undoubtedly, understanding the molecular basis of specificity in the interaction between HK and RR couples as well as the complete catalytic mechanism between these two molecules in the signaling process is especially important from many viewpoints, including the medical, and recent advances in the structural and biochemical field have contributed decidedly.

Further reading: Two-Component Systems in Bacteria

from writing in Two-Component Systems in Bacteria:

Further reading: Two-Component Systems in Bacteria

from Stefanie Vogt, Nicole Acosta, Julia Wong, Junshu Wang and Tracy Raivio writing in Two-Component Systems in Bacteria:

The CpxA membrane bound sensor kinase utilizes a periplasmic sensing domain to detect a wide variety of stresses to the bacterial envelope. This information is communicated via typical two-component phosphotransfer mediated reactions to the response regulator CpxR. Phosphorylated CpxR binds upstream of numerous promoters to mediate adaptation. Initial studies of CpxA inducing signals and CpxR regulated genes demonstrated a role for this two-component system in responding to protein misfolding in the envelope. In this chapter, we discuss recent progress regarding the mechanisms of signal detection, transduction, and gene regulation employed by CpxA and CpxR. The data indicate that the majority of inducing cues are sensed through the periplasmic domain of CpxA and lead to the relief of one or more inhibitory controls that function to maintain Cpx pathway activity at low basal levels in the absence of envelope stress. Some activating signals also enter the pathway downstream of CpxA, in the cytoplasm. Analysis of the Cpx regulon in multiple organisms indicates that, in addition to regulating the production of well studied envelope protein folding and degrading factors, CpxA and CpxR also control the expression of cellular functions linked to cell wall modification, transport, translation, and regulation, indicating that adaptation to envelope stress involves broad changes in cellular physiology. The Cpx two-component system has been shown to impact virulence in a number of pathogens, and our current knowledge of this field is discussed.

Further reading: Two-Component Systems in Bacteria

from David J. Clarke writing in Two-Component Systems in Bacteria:

The Rcs phosphorelay is a complex signaling network that is restricted in distribution to the Enterobacteriaceae. The core Rcs phosphorelay is composed of 3 proteins: the sensor kinase RcsC, the HPt domain protein RcsD and the response regulator RcsB. In addition to these core components the Rcs phosphorelay also contains some auxiliary proteins that are involved in mediating the inputs to and outputs from this signaling pathway. Therefore RcsF is a lipoprotein involved in signal perception, IgaA inhibits the activity of the phosphorelay and RcsA is required for the expression of some of the genes that are regulated by the phosphorelay. Whilst initially identified as a positive regulator of capsule production in Escherichia coli the Rcs phosphorelay is now recognized as a key regulator of motility, biofilm formation and virulence in many members of the Enterobacteriaceae.

Further reading: Two-Component Systems in Bacteria

from Turán P. Ürményi, Deivid C. Rodrigues, Rosane Silva and Edson Rondinelli writing in Stress Response in Microbiology:

Trypanosoma cruzi, the causal agent of Chagas' disease, is a flagellated protozoan parasite with a complex life cycle that involves infecting an insect and a mammalian host. Several environmental stresses occur during its life cycle, such as heat, reactive oxygen species, and osmolarity changes, and the parasite has evolved a variety of stress responses to cope with these challenges. The stress responses range from synthesis of several proteins and small molecules to modulation of the activity of organelles, and they are essential for the parasite's viability and survival in both hosts. Here we review the components and operation of T. cruzi's stress response with emphasis on its relevance to the parasite's biology and to Chagas' disease transmission, pathogenesis and treatment.

Further reading: Stress Response in Microbiology   Related publications

from Jose M. Requena writing in Stress Response in Microbiology:

Leishmania parasites are unicellular protozoa descending from one of the oldest eukaryotic lineages. During its digenetic life cycle, Leishmania alternates between the alimentary tract of the sandfly vector as an extracellular promastigote and the acidic phagolysosomes of macrophage cells as an intracellular amastigote. Parasites must cope with varied and heterogeneous environments: changes in temperature, in pH, in nutrient and oxygen concentrations. Also, they must face the immune defences, such as complement factors, free radicals and other antimicrobial effectors. The focus of this chapter will be on our current knowledge of the different stress responses in Leishmania, ranging from description of the prototypical heat shock response to more specific responses found in this parasite. A comprehensive view on the implications of the stress response in parasite survival, in cytodifferentiation and in apoptotic processes will be presented. Future studies, which should be directed mainly to the uncovering of the stress sensors, signal transduction pathways and regulatory mechanisms leading to the induction of the appropriate stress response will be also discussed.

Further reading: Stress Response in Microbiology   Related publications

from Valerie A. Ray and Karen L. Visick writing in Two-Component Systems in Bacteria:

The symbiotic relationship between the marine bioluminescent bacterium Vibrio fischeri and its host, the Hawaiian bobtail squid Euprymna scolopes, depends upon the ability of the two partners to sense and respond to each other. V. fischeri colonizes a specialized squid organ called the light organ in three general stages: initiation, accommodation, and persistence. To respond to the different environments encountered during these stages of colonization, V. fischeri utilizes specialized two-component signal transduction systems to regulate processes such as biofilm formation, motility and chemotaxis, and luminescence. In this chapter, we discuss in detail the two component systems that regulate these processes and how they impact successful colonization of the squid host.

Further reading: Two-Component Systems in Bacteria

from Karen Schrecke, Anna Staroń and Thorsten Mascher writing in Two-Component Systems in Bacteria:

The cell envelope stress response (CESR) network monitors and maintains envelope integrity to counteract the damaging effects of cell wall antibiotics and membrane perturbating agents. Two-component systems (2CSs) involved in orchestrating CESR in Firmicutes bacteria (low G+C Gram-positive) are characterized by so-called intramembrane-sensing histidine kinases (IM-HKs). The N-terminal input domain of these proteins consists of two transmembrane helices with a very short extracellular linker of less than 20 amino acids, which is insufficient for stimulus perception. It was originally thought that these HKs sense their stimuli within the membrane interface. But subsequent studies identified accessory membrane proteins for all IM-HKs described so far. This chapter will specifically summarize the current state of knowledge on BceRS- and LiaRS-like 2CSs, which are ubiquitously distributed in Firmicutes bacteria. While BceRSAB-like systems represent antibiotic-specific detoxification modules, LiaFSR-like three-component systems mount more general CESR. These two types of systems are genetically and functionally linked to BceAB-like ABC transporters and LiaF-like membrane-anchored regulatory proteins, respectively, which play a crucial role in sensing envelope stress and transferring the information to the cognate HKs. Accordingly, BceS- and LiaS-like IM-HKs do not function as sensor proteins, but rather as signal transfer relays between the sensor and the cognate response regulators.

Further reading: Two-Component Systems in Bacteria

from writing in Two-Component Systems in Bacteria:

Further reading: Two-Component Systems in Bacteria

from Juan-Francisco Martín, Alberto Sola-Landa and Antonio Rodríguez-García writing in Two-Component Systems in Bacteria:

Two-component systems (TCS) play a very important role in the regulation of metabolism in Streptomyces species in response to different nutritional or environmental signals. Streptomyces are Gram-positive soil-dwelling filamentous bacteria with large genomes that have the ability to produce thousands of different secondary metabolites. Streptomyces genomes contain a large number of paired two-component systems (usually more than 70) and some additional orphan sensor kinases and response regulators. Several of these systems have been studied in detail in the model species Streptomyces coelicolor. Particular attention has been paid to the PhoR/PhoP and the orphan GlnR systems due to their relevance in the control of primary metabolism and secondary metabolite biosynthesis. The PhoP binding sequence in many phosphate regulated promoters is formed by 11 nucleotide direct-repeats. A cross-talk between PhoP and other global regulators such as AfsR or GlnR has been found. Other two-component systems, particularly AbsA1/AbsA2, also control antibiotic biosynthesis in S. coelicolor, while others control chitinase synthesis, stress responses or cellular differentiation. Finally, some orphan response regulators named atypical response regulators (e.g. RedZ in S. coelicolor and JadR1 in Streptomyces venezuelae) bind as ligands the final product of the antibiotic biosynthetic pathway and act as feedback regulators of the biosynthesis of these secondary metabolites.

Further reading: Two-Component Systems in Bacteria

from writing in Two-Component Systems in Bacteria:

Further reading: Two-Component Systems in Bacteria

from writing in Two-Component Systems in Bacteria:

Further reading: Two-Component Systems in Bacteria

from Daniela Keilberg, Stuart Huntley and Lotte Søgaard-Andersen writing in Two-Component Systems in Bacteria:

The Myxococcus xanthus lifecycle is characterized by many social interactions. In particular, M. xanthus forms cooperatively spreading colonies in the presence of nutrients and multicellular, spore-filled fruiting bodies in the absence of nutrients. Formation of both cellular patterns depends on two intact motility systems. Moreover, fruiting body formation depends on intercellular communication and temporally regulated gene expression. The M. xanthus genome encodes a staggering 272 putative proteins of two-component system and most aspects of the M. xanthus lifecycle are regulated by one or more of these proteins. Interestingly, many of the corresponding genes encoding two-component system proteins possess an unusual organization in complex genes clusters and as orphan genes. However, major strides have been made in our understanding of a large number of these proteins. Here, we focus on the function of well-studied proteins of two-component systems in motility and development in M. xanthus.

Further reading: Two-Component Systems in Bacteria

from Juan A. Ayala, Felipe Cava and Miguel A. de Pedro writing in Stress Response in Microbiology:

The cell envelope is the major line of defence against environmental threats. It is an essential but vulnerable structure that shapes the cell and counteracts the turgor pressure. It provides a sensory interface, a molecular sieve and a structural support, mediating information flow, transport and assembly of supramolecular structures. Therefore, maintenance of cell envelope integrity in the presence of deleterious conditions is crucial for survival. Several envelope stress responses, including two components regulatory systems (TCRS), of Escherichia coli are involved in the maintenance, adaptation and protection of the bacterial cell wall in response to a variety of stresses. Recent studies indicate that these stress responses exist in many Gram negative pathogens. Particular emphasis has been made on the identified TCRS and their activating signals. Another aspect of stress response is the generation of morphological modifications. Most bacteria alter shape when growth conditions change and upon symbiotic or parasitic processes. Any modification in cell shape is connected with cell wall metabolism and requires specific regulatory mechanisms. Recent advances support the existence of complex mechanisms mediating morphological responses to stress involving inter and intra-specific signalling.

Further reading: Stress Response in Microbiology   Related publications

from W. Brian Whitaker and E. Fidelma Boyd writing in Stress Response in Microbiology:

Members of the genus Vibrio are Gram-negative ubiquitous marine bacteria. They can be isolated directly from the water column but are perhaps most known for their association with eukaryotic organisms. In their association with eukaryotic hosts, be it pathogenic or symbiotic, these bacteria must respond to a variety of stress conditions present within the host environment. Often times, these stress response systems are vitally important for the vibrios to successfully establish in the host. Here, we will discuss the systems used by the three main human pathogens of the genus, V. cholerae, V. parahaemolyticus, and V. vulnificus as well as briefly discussing the stress response systems of V. fischeri, V. splendidus, and V. anguillarum, all of which form close associations with marine organisms.

Further reading: Stress Response in Microbiology   Related publications

from Maria J. Figueras, Sergio O. Angel, Verónica M. Cóceres and Maria L. Alomar writing in Stress Response in Microbiology:

Toxoplasma gondii is an important pathogen of human and domestic animals. It has a complex life cycle which includes the transition from one host to another, being only exposed to the environment during one stage, as highly resistant oocysts. Interestingly, in the intermediate host (non-feline mammalians and birds) the parasite presents an asexual cycle with two stages that can interconvert without its passage in the definite host (felines). The asexual cycle is very important in the establishment of the infection and on its pathogenesis and it could be driven by different kind of stressors. Therefore, the response to environmental and host stresses is essential to their viability and successful progression through their life cycle. The heat shock proteins are key molecules not only in the resistance to different stressors, but they are also involved in the optimal differentiation as well as in other biological processes in T. gondii. This chapter summarizes the findings on different aspects of T. gondii stress responses and the implication of these processes in the biology and pathogenesis of this parasite.

Further reading: Stress Response in Microbiology   Related publications