"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 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.

Further reading: Two-Component Systems in Bacteria

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

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

"As in the first edition Graumann has brought together top authors who critically review the high-level topics and classify the current literature in an excellent manner ... This carefully edited book of Graumann's should be in the collection of every group that works with B. subtilis." from Erhard Bremer (Marburg) writing in Biospektrum (2012) 18: 681. read more ...

Bacillus: Cellular and Molecular Biology (Second edition) Edited by: Peter Graumann ISBN: 978-1-904455-97-4 Publisher: Caister Academic Press Publication Date: February 2012 Cover: hardback "carefully edited book" (Biospektrum)

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 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 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

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 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 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 Patrick Eichenberger writing in Bacillus: Cellular and Molecular Biology (Second edition):

Bacteria of the genera Bacillus and Clostridium can be found in two distinct states. In the vegetative state, bacteria are metabolically active and use available nutrients to grow and divide by binary fission, a process that generates two identical daughter cells. By contrast, when nutrients are scarce, a developmental program of endospore formation (sporulation) is initiated, resulting in the production of highly resistant spores. In the spore state, bacteria are metabolically dormant, and their genetic material, protected in the core of the spore, can endure a variety of challenges, including exposure to radiation, elevated temperatures and noxious chemicals. Sporulation is a complex process, which requires the generation of two distinct cell types: a forespore and a larger mother cell. The progression of the developmental program is controlled by two exquisitely regulated cell type-specific lines of gene expression that run in parallel and are connected at the post-translational level. Various genetic screens and genome-wide transcriptional analyses have identified more than 600 genes that are expressed in the course of sporulation. The function of several of these genes has been characterized in detail and subcellular localization data are available for at least 90 sporulation proteins. Thus, sporulation constitutes one of the best characterized developmental programs at the molecular and cellular levels.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Kürşad Turgay writing in Bacillus: Cellular and Molecular Biology (Second edition):

Proteolysis is an important part of many fundamental cellular processes. The intricate involvement of proteases and peptidases in protein quality control, general stress response, control of regulatory networks and development in Bacillus subtilis are introduced in this review. Especially the more recent developments on the role of AAA+ proteins and their adaptor proteins in regulated and general proteolysis and the role of regulated intra-membrane proteolysis and membrane proteases in signal transduction are discussed.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

"The book contains some very high quality diagrams and figures ... It also comes with useful Internet tools ... This comprehensive book presents current scientific studies on the cellular processes of Bacillus species ... The book is well organized" from Rebecca T. Horvat (University of Kansas, USA) writing in Doodys read more ...

Bacillus: Cellular and Molecular Biology (Second edition) Edited by: Peter Graumann ISBN: 978-1-904455-97-4 Publisher: Caister Academic Press Publication Date: February 2012 Cover: hardback "high quality diagrams and figures" (Doodys)

from Begoña Carrasco, Paula P. Cardenas, Cristina Cañas, Tribuhwuan Yadav, Carolina E. César, Silvia Ayora and Juan C. Alonso writing in Bacillus: Cellular and Molecular Biology (Second edition):

All organisms have developed a variety of DNA repair mechanisms to cope with DNA lesions. Homologous recombination (HR), which uses a homologous template to restore lost information at the break site, is the ultimate step for repair of one- or two-ended double strands breaks (DSBs) and for promoting the re-establishment of replication forks. Genetic and cytological approaches were used to analyze the requirements of exponentially growing Bacillus subtilis cells to survive chemical or physical agents that generate one- or two-ended DSBs and the choreography of DSB repair. The damage-induced multi-protein complex (recombinosome), organised into focal assemblies, has been confirmed by biochemical approaches. HR is coordinated with other essential processes, such as DNA replication, transcription and chromosomal segregation. When DSB recognition or end resection is severely impaired or an intact homologous template is not available the DNA ends of two-ended DSBs are repaired via non-homologous end joining.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Berenike Maier writing in Bacillus: Cellular and Molecular Biology (Second edition):

Competence for transformation enables bacteria to take up exogenous DNA. The imported DNA can integrate into the chromosome by homologous recombination or anneal to form a self replicating plasmid. Development of competence in Bacillus subtilis is tightly regulated as a function of cell density during entry into the stationary growth phase. Additionally, competence occurs only in a small subpopulation of B. subtilis cells. Development of competence is switch-like and controlled by the concentration of the master regulator ComK. Quantitative analysis at the single cell level in conjunction with mathematical modeling allowed understanding of development and decline of competence at the systems level. In the current model, a complex regulatory network maintains the concentration of ComK below a threshold concentration for switching into the competent state. In the stationary growth phase, noisy expression of ComK triggers competence development as individual cells reach the threshold concentration due to random fluctuations. Competent cells express specialized proteins (late competence proteins) for binding, importing, and recombining external DNA. Cytosolic and transmembrane proteins accumulate at a single or both cell poles. Application of external DNA triggers movement of various proteins involved in recombination away from the pole, most likely undergoing search for homologous regions on the chromosome. These findings provide good evidence for a concerted action of DNA import and recombination, promoting the idea that a spatially organized and modular multiprotein machine has evolved for efficient transformation. This machine powers efficient and irreversible DNA import and can work against considerable external forces.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Peter L. Graumann writing in Bacillus: Cellular and Molecular Biology (Second edition):

After a bit more than a decade of the use of GFP - or immuno-fluorescence microscopy to study bacterial chromosome segregation, it has become clear that this process is highly organized, temporally as well as spatially, and that a mitotic-like machinery exists that actively moves apart sister chromosomes. Several key factors in this process have been identified, and at least a rough overall picture can be drawn on how chromosomes are separated so highly rapidly and efficiently. Bacillus subtilis has a circular chromosome. Replication initiates at the origin of replication that is defined as 0 degrees, and two replication forks proceed bidirectionally to converge at the terminus region, which is defined as 180 degrees. All other regions on the chromosome are defined as the corresponding site on a circle. DNA replication occurs in the cell centre, and duplicated regions are moved away from the cell centre towards opposite cell poles. This process is driven by an active motor that involves bacterial actin-like proteins, whose mode of action is still unknown. A dedicated protein complex called SMC forms two subcellular centres that organize newly duplicated chromosome regions within each cell half, setting up the spatial organization that characterizes bacterial chromosome segregation. Several proteins, including topoisomerases, DNA translocases and recombinases, ensure that entangled sister chromosomes or chromosome dimers can be completely separated into the future daughter cells shortly before cell division occurs at the middle of the cells.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Frederico Gueiros-Filho writing in Bacillus: Cellular and Molecular Biology (Second edition):

Cell division is the process of generating two viable descendants from a progenitor cell. This involves two coordinated events: the replication and segregation of the bacterial chromosome and the splitting of the progenitor cell by cytokinesis, which in bacteria is also known as septum formation. Bacterial cells have developed a remarkably sophisticated protein machine capable of precisely splitting a progenitor cell at the right place and time in every cell cycle. This machine, which is known as the divisome or septalsome, is based on a contractile protein ring, as in the case of eukaryotes. In contrast to eukaryotic cells, however, which use actin and myosin in their contractile protein ring, the bacterial contractile machine is based on the tubulin-like protein FtsZ. Here we review the mechanism of cytokinesis in Bacillus subtilis.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Jan Maarten van Dijl, Annette Dreisbach, Marcin J. Skwark, Mark J.J.B. Sibbald, Harold Tjalsma, Jessica C. Zweers and Girbe Buist writing in Bacillus: Cellular and Molecular Biology (Second edition):

Bacterial homeostasis is largely determined by a phospholipid bilayer that encloses the cytoplasm. The proteins residing in this cytoplasmic membrane are responsible for communication between the cytoplasm and extracytoplasmic cell compartments or the extracellular milieu of the cell. This chapter deals with the cytoplasmic membrane proteome of Bacillus subtilis. Specifically, we address current views on the roles of membrane proteins in homeostasis, their membrane targeting and retention signals, machinery for membrane insertion, localization of membrane proteins, membrane protein degradation and, finally, the identified and predicted composition of the B. subtilis membrane proteome. Known mechanisms and knowledge gaps are discussed to give a comprehensive overview of the ins and outs of the B. subtilis membrane proteome.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from José Eduardo González-Pastor writing in Bacillus: Cellular and Molecular Biology (Second edition):

Most of the knowledge about Bacillus subtilis derives from studies of laboratory strains growing as planktonic cultures, in which all the individual cells are considered identical. Recently, the study of a natural and undomesticated isolate has revealed that B. subtilis cells display multicellular and social features that were lost in the laboratory strains, which were selected over generations for easy manipulation. In undomesticated strains, certain environmental conditions trigger cells of this bacterium to form multicellular communities where sporulation takes place, and to exhibit some particular social traits, like swarming motility and the fratricide of sibling cells or cannibalism during sporulation. Interestingly, some of these behaviours are based in the heterogeneity of the B. subtilis populations, which has been determined using cell biological techniques like fluorescence and light microscopy. This chapter outlines the genetic pathways governing the transition from a unicellular to a multicellular stage, swarming motility and cannibalism. The biological relevance of these alternative lifestyles is discussed.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Marie-Françoise Noirot-Gros, Patrice Polard and Philippe Noirot writing in Bacillus: Cellular and Molecular Biology (Second edition):

Eubacteria have evolved multicomponent protein machines, termed replisomes, which duplicate their chromosomes rapidly and accurately. Extensive studies in the model bacteria Escherichia coli and Bacillus subtilis have revealed that in addition to the replication core machinery, other proteins are necessary to form a functional replication fork. Specific subsets of proteins mediate: a) the assembly of the replisome at the chromosomal origin of replication [initiation]; b) the progression of the replication forks along the chromosome [elongation] and their maintenance by providing solutions for replication restart, which are adapted to overcome possible 'roadblocks' encountered on the DNA template; and c) the physiological arrest of replication when chromosome duplication is completed [termination]. Within the cell, DNA replication takes place within a factory positioned at the cell centre. This review summarises recent knowledge about chromosomal replication in Bacillus subtilis and related Gram-positive bacteria. It is focused on the events governing the assembly and the fate of the replication fork, describes protein networks connected with the replisome, and emphasises several novel aspects of DNA replication in this group of bacteria.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Wade C. Winkler writing in Bacillus: Cellular and Molecular Biology (Second edition):

Bacterial genetic regulation is generally assumed to occur at the level of transcription initiation through the use of transcription factors. Regulatory mechanisms that take place post-transcription initiation are sometimes treated as anomalies - as exceptions to the rule. However, the actual degree of usage for post-initiation regulatory strategies in bacteria still remains to be fully determined. As evidence to this fact, recent research has significantly expanded the general understanding of post-initiation regulation in Bacillus subtilis and other bacteria. Regulatory RNAs are now predicted to control expression of numerous fundamental biochemical pathways that together constitute greater than 4% of the B. subtilis genome. Therefore, post-initiation regulation is a vital layer of bacterial genetic circuitry that still remains to be fully revealed.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Rut Carballido-López writing in Bacillus: Cellular and Molecular Biology (Second edition):

Prokaryotic cells possess filamentous proteins, analogous to eukaryotic cytoskeletal proteins, that play a key role in the spatial organization of essential cellular processes. The bacterial homologues of actin (MreB, ParM, MamK and AlfA and Alps proteins) are involved in cell shape determination, DNA segregation, cell polarity, cell motility and other functions that require the targeting and accurate positioning of proteins and molecular complexes in the cell. In Bacillus subtilis, MreB homologues (MreB, Mbl and MreBH) assemble into dynamic helical-like structures along the sidewalls, which control morphogenesis by actively directing the growth of the cylindrical cell wall (elongation). The ultimate morphology of the cell is believed to depend on a dynamic interplay between the intracellular MreB proteins and the extracellular proteins that carry up cell wall biosynthesis and degradation, probably linked through MreCD and/or other membrane proteins such as RodZ. Recent findings rule out an essential function of the MreB isoforms of B. subtilis in chromosome segregation, but it is still possible that MreB is involved in this process. The general properties of the MreB proteins, relative to eukaryotic actin and to other prokaryotic homologues of actin, and the known functions of the MreB cytoskeleton in B. subtilis and other bacteria, will be discussed in this chapter.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Dirk-Jan Scheffers writing in Bacillus: Cellular and Molecular Biology (Second edition):

The cell wall of Bacillus subtilis is a rigid structure on the outside of the cell that forms the first barrier between the bacterium and the environment, and at the same time maintains cell shape and withstands the pressure generated by the cell's turgor. In this chapter, the chemical composition of peptidoglycan, teichoic and teichuronic acids, the polymers that comprise the cell wall, and the biosynthetic pathways involved in their synthesis will be discussed, as well as the architecture of the cell wall. B. subtilis has been the first bacterium for which the role of an actin-like cytoskeleton in cell shape determination and peptidoglycan synthesis was identified and for which the entire set of peptidoglycan synthesizing enzymes has been localised. The role of the cytoskeleton in shape generation and maintenance will be discussed and results from other model organisms will be compared to what is known for B. subtilis. Finally, outstanding questions in the field of cell wall synthesis will be discussed.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)

from Peter Lewis and Xiao Yang writing in Bacillus: Cellular and Molecular Biology (Second edition):

The traditional view of transcription and translation within the cell was that of a very closely coupled process where translating ribosomes assembled on the nascent transcript as it was produced by transcribing RNA polymerase. Whilst this close physical coupling is undoubtedly important, it seems clear now that a number of other events are significant with respect to the physical organization of these two processes within the cell. Transcription is crudely segregated into two regions within the nucleoid where either stable (r- and t-) RNA, or mRNA transcription predominate. Translation by polysomes is probably enriched at cell poles, whereas the assembly of initiation complexes, and maybe some transcriptionally linked ribosomes may occur throughout the nucleoid.

Further reading: Bacillus: Cellular and Molecular Biology (Second edition)