"Written by leading scientists the 13 chapters of this book reflect a competent and current overview of the current state of knowledge ... high quality content " from Thorsten Mascher (Munich, Germany) writing in Biospektrum (2013) 19: 107-111 read more ...

Bacterial Regulatory Networks Edited by: Alain A.M. Filloux ISBN: 978-1-908230-03-4 Publisher: Caister Academic Press Publication Date: June 2012 Cover: hardback "a competent and current overview" (Biospektrum)

"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 Charles J. Dorman writing in Bacterial Regulatory Networks:

H-NS is an abundant DNA binding protein that has been found to influence the expression of hundreds of genes in those Gram-negative bacteria, chiefly Escherichia coli and Salmonella enterica, where its regulatory effects have been investigated. It also has the potential to organize the structure of the nucleoid. H-NS has a preference for binding to A+T-rich DNA and this preference underlies its targeting of genes that have been acquired by horizontal transfer. H-NS usually acts as a transcriptional silencer by binding to a nucleation site followed by lateral spreading with or without the creation of DNA-protein-DNA bridges; it may also act as an architectural component in the nucleoid. Bacteria use a multitude of mechanisms to displace H-NS or to attenuate its negative influence on gene expression. A paralogue of H-NS, called StpA, is an efficient RNA chaperone and controls a regulon of genes in S. enterica by influencing expression of the RpoS sigma factor. Orthologues of H-NS have been discovered on large self-transmissible plasmids, introducing a new dimension in considerations of the roles of H-NS-like proteins in horizontal gene transfer. Importantly, analogues of H-NS are now being discovered and characterized in Gram-negative bacteria such as Pseudomonas that are only distantly related to E. coli, in the medically important actinomycete Mycobacterium tuberculosis and even in Gram-positive organisms such as Bacillus subtilis.

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from Jeroen Siebring, Robin A. Sorg, Martijn Herber, Oscar P. Kuipers writing in Bacterial Regulatory Networks:

Bistable switches occur in regulatory networks that can exist in two distinct stable states. Such networks allow distinct switching of individual cells. In bacteria these switches coexist with regulatory networks that respond gradually to environmental input. Bistable switches play key roles in high investment processes such as cellular differentiation in which only the end-result of the process is functional. Bistable switches are involved in development of phenotypical traits, such as virulence, bacterial persistence, sporulation and production of valuable compounds like antibiotics. The phenomenon of bistable networks is here explained and discussed. Additionally, natural and evolutionary solutions for creating all-or-none regulatory decisions are described as well as the use of bistable networks in synthetic biology.

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from Zulma R. Suárez-Moreno, Juan F. González, Giulia Devescovi and Vittorio Venturi writing in Bacterial Regulatory Networks:

Bacteria regulate gene expression in a population dependent manner using a sophisticated mechanism based on the production and sensing of chemical signals, known as quorum sensing. Such synchronized response in bacterial populations constitutes a form of multicellularity and enables adaption and survival in challenging environments. Although current evidence shows that the predominant signaling molecules produced by Gram-negative bacteria are N-acyl derivatives of homoserine lactones (AHLs), bacteria use a wide variety of signals. In this chapter we provide an overview of quorum sensing in Gram-negative bacteria, and discuss current and future trends in this field of research.

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from Pierre Cornelis and Simon C. Andrews writing in Bacterial Regulatory Networks:

For the vast majority of bacteria, iron is an essential element that is not readily available due to the poor solubility of the oxidized Fe3+ form that prevails aerobically. Because of this, bacteria inhabiting aerobic niches often suffer deficiencies in iron supply. Pathogenic bacteria experience a particularly acute form of iron-restriction. This arises from the host's 'iron-withdrawal response' to infection, whereby iron availability is constrained by increasing lactoferrin (an iron-chelating, bacteriostatic, extracellular glycoprotein) levels and reducing the degree of iron saturation for the circulating iron-transport protein, transferrin. The importance of iron to bacteria stems from its multiple metabolic roles. Examples of its crucial metabolic involvement include redox-stress resistance (e.g. heme-bearing catalases) and DNA manufacture (di-Fe containing ribonucleotide reductases). Although indispensible, iron is an unfriendly, hazardous metal as the Fe2+-triggered Fenton reaction produces destructive reactive oxygen species (ROS) such as superoxide (O2-), hydrogen peroxide (H₂O₂) as well as the highly reactive hydroxyl radical (˚OH).

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from Efthimia Lioliou, Cédric Romilly, Thomas Geissmann, François Vandenesch and Pascale Romby writing in Bacterial Regulatory Networks:

Many pathogenic bacteria cause serious diseases in humans, animals, and plants. Due to the appearance of resistance to multiple antibiotics, it has become important to fully understand the regulatory networks that lead to the production of virulence factors that help the bacteria combat the host defense machinery, acquire nutrients, and survive and/or proliferate within the host. In recent years, complex interplays between transcriptional regulatory proteins, two-component systems, and regulatory RNAs have been described, establishing the gene expression patterns in pathogenic bacteria. In this review, several examples will illustrate the diversity of regulatory RNAs and how they are integrated into the regulatory circuits required for virulence gene expression, with special emphasis on the mechanisms of regulation at the molecular level.

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from David E. Whitworth writing in Bacterial Regulatory Networks:

Two-component systems (TCSs) are signalling pathways found abundantly in prokaryotes, and they are the dominant mechanism for stimulus-responsive adaptation in such organisms. An ever-increasing number of physiological phenomena are known to be regulated by TCSs, including cell cycle progression, pathogenesis, motility, and biofilm formation. The basic TCS comprises a receptor protein (sensor kinase) which autophosphorylates in response to a stimulus. The phosphoryl group is then directly transferred to a response regulator protein (the second component) that has a phosphorylation-dependent effector function. While the most basic TCSs are relatively well understood, there are many 'atypical' systems, which exhibit additional mechanistic features (for instance, regulation of sub-cellular location, intrinsic and extrinsic phosphatase activities, and cross-communication between TCSs), adding complexity to their signalling properties. The relatively recent availability of complete prokaryotic genome sequences has also provided new opportunities to appreciate global features of TCS function. For example, analyses have provided insights into TCS evolution, which in turn have yielded computational methods for evaluating TCS protein partnerships. This chapter provides an overview of the common features of TCSs from a historical perspective, and then describes current understanding regarding the mechanisms of TCS function. Finally, outstanding questions regarding TCS function are discussed.

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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 Ernesto Perez-Rueda, Nancy Rivera-Gomez, Mario Alberto Martinez-Nuñez and Silvia Tenorio-Salgado writing in Bacterial Regulatory Networks:

The capabilities of organisms to contend with environmental changes depend on their repertoire of genes and their ability to regulate their expression. DNA-binding transcription factors have a fundamental role in this process, because they regulate transcription positively or negatively as a consequence of environmental signals. In this chapter we briefly describe some of the most recent findings on regulatory network evolution from the perspective of DNA-binding transcription factors. We explore diverse elements associated with the evolution of regulatory networks, such as gene duplication, where new interactions can emerge together with their upstream and downstream binding sites. The chapter is divided into sections covering the evolution of transcription factors and their domains, their evolution, and a global analysis. Hypotheses concerning a comprehensive picture of how regulatory networks have evolved in prokaryotes and the role of transcription factors in this organization are discussed.

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from Karlijn C. Bastiaansen, Wilbert Bitter and María A. Llamas writing in Bacterial Regulatory Networks:

Gene expression in bacteria is mainly controlled at the level of transcription initiation. To achieve this process a number of different mechanisms have evolved, one of which is the utilization of alternative sigma factors. Sigma factors are small proteins that associate with the RNA polymerase core enzyme (RNAPc) and direct it to specific promoter sequences, where they initiate gene transcription. Bacteria are able to regulate transcription initiation by synthesizing and activating different sigma factors that recognize different promoter consensus sequences. The largest group of alternative sigma factors consists of the so-called extracytoplasmic function (ECF) sigma factors that regulate gene expression in response to cell envelope stresses or environmental stimuli. The activity of ECF sigma factors is controlled by anti-sigma factors and a complex cascade of regulated (proteolytic) modifications. In gram-negative bacteria, ECF sigma factors are also controlled by cell-surface signalling (CSS), a regulatory system that includes an outer membrane receptor in the signal transduction pathway. In this chapter we will discuss the general composition and function of ECF sigma factors and their role in cell envelope stress responses and CSS.

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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 J. Maxwell Dow, Yvonne McCarthy, Karen O'Donovan, Delphine Caly and Robert P. Ryan writing in Bacterial Regulatory Networks:

Cyclic di-GMP is now recognised as an almost universal second messenger in eubacteria that acts to regulate a wide range of functions including developmental transitions, adhesion, biofilm formation, motility and the synthesis of virulence factors. Cyclic di-GMP is synthesised from two GTP molecules by diguanylate cyclases that have a GGDEF domain and degraded by phosphodiesterases with either an EAL or HD-GYP domain. These proteins often have associated signal input domains, suggesting that their enzymatic activity may be modulated by different environmental or cellular cues. Cyclic di-GMP exerts a regulatory action through binding to diverse receptors that include a small protein domain called PilZ, transcription factors, enzymatically-inactive GGDEF, EAL or HD-GYP domains and riboswitches. The multiplicity of GGDEF, EAL and HD-GYP proteins together with a range of receptors within the same bacterial cell indicates the considerable complexity of cyclic di-GMP signalling. This has led to the concept of discrete pools of the nucleotide that are generated locally and act to influence intimately associated targets. A number of signalling proteins may be organised in a regulatory network to control a common function(s). Understanding cyclic di-GMP signalling may afford strategies for inhibition of biofilm formation and virulence factor synthesis in bacterial pathogens.

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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 Patricia C. Burrows, Simone C. Wiesler, Zhensheng Pan, Martin Buck and Sivaramesh Wigneshweraraj writing in Bacterial Regulatory Networks:

Amongst the many accessory factors that bind RNA polymerase (RNAp) and serve to control its activities, sigma (σ) factors ubiquitously feature in programming of gene expression in response to abiotic and biotic cues. Here we review the role of the major variant σ factor, σ54, in the expression of gene sets used for establishing the virulence of a wide range of pathogenic bacteria. The tight coupling of σ54-dependent transcription to signalling pathways underpins the regulation of such systems, and allows a wide dynamic range of gene expression.

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from Kathryn A. Scott, Elizabeth E. Jefferys, Benjamin A. Hall, Mark A. J. Roberts and Judith P. Armitage writing in Bacterial Regulatory Networks:

Chemotaxis is the process by which bacteria migrate towards environments that are favourable for growth. Changes in the concentration of attractants or repellents are detected by receptors, which are usually transmembrane proteins. These receptors transduce the signal to the interior of the cell where a two-component system ultimately leads to changes in motile behaviour. Chemotaxis emerged as a beneficial trait for survival early in the evolution of bacteria and archaea. A core set of proteins is common to the chemosensory networks in many different species. During the evolution of bacteria this core network has diversified and expanded. Here we describe the conserved apparatus in the steps necessary for chemotaxis; sensing of chemoeffectors, signalling to the motility apparatus, rapid signal termination, and adaptation. We then highlight examples from species with complex chemosensory networks to illustrate the variations in chemotactic apparatus that have arisen from the common core.

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from Petra Tielen, Max Schobert, Elisabeth Hartig and Dieter Jahn writing in Bacterial Regulatory Networks:

Survival and growth during periods of low oxygen tension are essential for the successful colonization of natural habitats by bacteria. For the coordination of the necessary biochemical adaption processes upon oxygen deprivation bacteria employ a fine tuned interplay of various regulatory proteins and sRNAs. The iron sulfur cluster containing oxygen sensor Fnr and its multiple variants are often found involved in the corresponding regulatory networks throughout the bacterial kingdom. Similarly, the alternative electron acceptor nitrate is usually detected by the two-component system NarXL and its derivatives. In contrast, other systems including the quinone pool responsive two component system ArcBA, the ResDE system or the regulatory sRNAs FnrS and ArcZ are limited to certain bacterial groups. Here we describe the regulatory networks and their components underlying the adaption processes of the model bacteria Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis to an anaerobic life style.

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from Eberhard Klauck and Regine Hengge writing in Bacterial Regulatory Networks:

The σ^S (RpoS) sigma subunit is the master regulator of the general stress response in Escherichia coli, which controls the expression of more than 500 genes during entry into stationary phase or upon exposure to many different stress conditions. σ^S is present at very low levels only in rapidly growing cells, but multiple stress signals are integrated in a way that results in strong σ^S accumulation and efficient σ^S-containing RNAP holoenzyme (Eσ^S) formation. The first part of this review summarizes the molecular control mechanisms of switching from the "low-σ^S" to "high-σ^S" state, which operate at the levels of rpoS transcription, rpoS mRNA turnover and translation, σ^S proteolysis and Eσ^S formation, and outlines multiple stress signal integration into these highly interconnected regulatory processes. We then show that, despite its complexity, the σ^S control network essentially is an intricate combination of a few typical network motifs. These are several key feedforward loops that control σ^S expression, a central and homeostatic negative feedback loop that integrates post-transcriptional σ^S control mechanisms, mutual inhibition of sigma factors competing for RNAP core enzyme governing σ^S activity control, and a series of smaller positive feedback loops that seem to stabilize the "high-σ^S" state.

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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)