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.

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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.

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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.

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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.

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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.

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