from Brandon L. Coyle, Weibin Zhou and François Baneyx writing in Bionanotechnology: Biological Self-assembly and its Applications:

Designer proteins combine the adhesive or synthesizing properties of solid binding peptides (SBPs) selected by combinatorial techniques with the desirable characteristics of a host scaffold. Like natural biomineralizing proteins, these chimeric constructs are powerful tools to control the nucleation, growth, morphogenesis and crystallography of inorganic phases. They also hold great potential for the assembly of hybrid structures in which inorganic, biological and synthetic components are organized with the high degree of precision needed to take advantage of the unique properties of matter at the nanoscale. After briefly discussing common approaches for identifying SBPs, we discuss the mechanisms by which they modulate materialization, which variables influence the process, and review recent progress in the use of designer proteins to fabricate complex architectures.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

from Jenny Draper, Jinping Du, David O. Hooks, Jason Lee, Natalie Parlane and Bernd H.A. Rehm writing in Bionanotechnology: Biological Self-assembly and its Applications:

Biopolyesters are a class of carbon storage polymers synthesized by a wide variety of bacteria in response to nutrient stress. Production of these polyhydroxyalkanoates (PHAs = polyesters) is catalyzed by PHA synthases, which polymerize (R)-3-hydroxyacyl-CoA thioesters into polyester. There are several different classes of PHA synthases which preferentially utilize different CoA thioester precursors, generating PHAs with varying material properties such as elasticity and melting point. Genetic engineering and growth on varied carbon sources can be used to modify the type of polyester produced. The general biopolyester properties of biocompatibility, biodegradability, and production from renewable carbon sources have led to considerable interest in PHAs as biomaterials for medical applications as well as alternatives to petrochemical plastics. Biopolyesters are generated in the cell as water-insoluble granules coated with structural, regulatory, and synthase proteins. Recently, the natural structure of the granules has been exploited to generate functionalized nanoparticles for use in a wide variety of applications, including bioseparation, drug delivery, protein purification, enzyme immobilization, diagnostics, and vaccine delivery.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

from Anisha David, Sunita Yadav and Satish Chander Bhatla writing in Bionanotechnology: Biological Self-assembly and its Applications:

Although oil bodies are present in a wide variety of tissues in plants, it is their abundance in the oilseed cotyledons that has been most extensively investigated for their biogenesis, structure, physiological roles, isolation and biotechnological applications. The phospholipid monolayer membrane of the oil bodies encasing the triacylglycerol (TAG) matrix not only possesses a set of structural and functional proteins (oleosins, steroleosins and caleosins), they also exhibit quite a few enzymatic and non-enzymatic proteins on their surface (lipoxygenase, protease and phospholipase) whose expression is transient and depends on the stage of oil body mobilization during seed germination. These transiently expressed signalling molecules are under the influence of various environmental and consequent physiological factors for their roles in oil body mobilization during seed germination. Based on these features of oil bodies to attract and bind a variety of biomolecules on their surface, oil body preparations have been put to extensive biotechnological applications, which are also being discussed in this review.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

from Jonatha M. Gott writing in RNA Editing: Current Research and Future Trends:

Mitochondrial RNAs in the acellular slime mold Physarum polycephalum are subject to the widest range of editing events observed thus far. Mitochondrial RNAs differ from the mitochondrial genome at over 1300 sites, and both coding (mRNAs) and non-coding RNAs (rRNAs and tRNAs) are affected. At least three distinct editing mechanisms are needed to account for the different forms of editing observed in the mitochondrial transcriptome: nucleotide insertions and deletions, C to U changes, and specific alterations at the 5' end of tRNAs. Nucleotide insertions are co-transcriptional and require flanking regions of the template, but the exact signals that specify the site of nucleotide insertion and the identity of the nucleotide to be added remain an enigma. The rare instances of base changes and replacement of the first nucleotide of mitochondrial tRNAs are not directly linked to transcription and are likely to occur via processes related to those previously described in other mitochondrial editing systems.

Further reading: RNA Editing: Current Research and Future Trends

from Mathieu Bennet, Teresa Perez-Gonzalez, Dean Wood and Damien Faivre writing in Bionanotechnology: Biological Self-assembly and its Applications:

Magnetotactic bacteria are microorganisms that form chains of magnetic nanoparticles. This process represents one of the most advanced examples of biological self-assembly at the nano- and micrometre scale. In fact, the nanoparticle size and morphology, together with the arrangement are controlled at the genetic level. The resulting hierarchical structure bestowing its magnetic properties to the bacteria is of utter interest to the development of bio-inspired nanotechnological self-assemblies. In this review, we describe the characteristics of the bacterial magnetic assembly with reference to the latest model found in the scientific literature. The roles of the magnetic dipoles interactions and of bacterial membrane proteins to achieve a stable, optimised and effective magnetic assembly are assessed and the relevant bio-inspired self-assembly scientific works are reviewed.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

from Matthew R. Preiss, Anju Gupta and Geoffrey D. Bothun writing in Bionanotechnology: Biological Self-assembly and its Applications:

Liposome-nanoparticle assemblies (LNAs) combine the demonstrated potential of clinically approved nanoparticles and liposomes to achieve multiple therapeutic and diagnostic objectives. Efficient and effective biomedical application requires assemblies to be stable, biocompatible, and bioavailable, while enhancing the properties of encapsulates. LNAs have been demonstrated to be effective for in vivo and in vitro providing targeting and stimuli-responsive delivery of therapeutic and imaging agents. The ability to design LNAs with nanoparticle encapsulation, bilayer-decoration, and surface coupling provides a variety of different structures and functions. While the potential of LNAs has been demonstrated, future investigation into the interaction between the lipid bilayer and nanoparticles is necessary to understand and develop LNAs for clinical applications. This section will discuss the current state of liposome-nanoparticle assembly design, characterization, and applications of liposome-nanoparticle assemblies.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

"... survey (of) some of the most striking and successful approaches to producing biogenic nanodevices ... consider(s) not only living organisms as manufacturers, but also applying the processes for the in vitro self-assembly of isolated biomolecules" from Ref. Res. Book News (February 2013) p265. read more ...

Bionanotechnology: Biological Self-assembly and its Applications Edited by: Bernd H. A. Rehm ISBN: 978-1-908230-16-4 Publisher: Caister Academic Press Publication Date: February 2013 Cover: hardback "the most striking and successful approaches" (Book News)

from Meng How Tan and Jin Billy Li writing in RNA Editing: Current Research and Future Trends:

RNA editing is a post-transcriptional mechanism whereby genomically encoded information is altered at the level of the transcript. We describe in this review how RNA editing sites can be identified. The pace of discovery in the past few decades was dependent on the sequencing technologies available at a particular time. At the beginning when DNA sequencing had just been developed and automated, the identification of RNA editing sites was slow and often occurred by chance. Over time, as more and more sequences were deposited in databases, it became possible for scientists to computationally mine the databases for more editing sites. In recent years, with the development of ultra-high throughput sequencing technologies whereby millions to billions of DNA molecules are sequenced simultaneously, scientists can now uncover RNA editing sites in a genome-wide manner. However, extra care has to be taken during the analysis process to remove artifacts and to ensure that true editing sites are identified.

Further reading: RNA Editing: Current Research and Future Trends

from Harold C. Smith writing in RNA Editing: Current Research and Future Trends:

Two decades of research revealed the mechanism for site-specific, apolipoprotein B (apoB) mRNA C to U editing and its developmental and metabolic regulation. The field began to lose momentum while many open questions remained. This was due to perceived impasses in translational research endpoints: (1) liver is the most significant organ in the metabolism of cholesterol- and triglyceride-rich lipoproteins and despite active and regulated hepatic editing in rodent models, human liver does not express the cytidine deaminase APOBEC1 required for apoB mRNA editing. (2) Mammals express APOBEC1 in their small intestines where 100% of the apoB mRNA is edited in adults but this activity is constitutive. (3) Expression of APOBEC1 is not essential for life in mice. In the past few years there has been a resurgence in interest because: (1) APOBEC1 edits the 3' UTRs of multiple mRNAs and either alone or together with its RNA-binding cofactor, A1CF, may regulate mRNA stability and translation in diverse tissues. (2) A1CF is required for embryological development, acting through a mechanism that may be unrelated to APOBEC1. (3) Discovery of dC to dU DNA mutational activity by APOBEC1 raises new questions of its oncogenic potential. This review will consider past and current discoveries relative to the exciting new research opportunities in the field.

Further reading: RNA Editing: Current Research and Future Trends

from Jorge Cruz-Reyes and Laurie K. Read writing in RNA Editing: Current Research and Future Trends:

The extraordinary RNA editing by U insertion and U deletion in mitochondrial mRNAs is arguably the best characterized process in kinetoplastids. However, much less is known about ancilliary factors of the editing multiprotein enzyme core. This enzyme architecture and basic catalysis guided by small non-coding gRNAs have enjoyed central stage, compared to other aspects in the biology of editing substrates, from biogenesis to translation. Many mRNAs and thousands of gRNAs are undoubtedly targeted by numerous factors that regulate unwinding, annealing, stability, assembly into editing enzymes, and translation. Recent years have seen a virtual explosion in the discovery of editing accessory factors. This review discusses the progress in this area, and frames a working model whereby the editing machinery is functionally and physically linked to pre and post editing events through a dynamic higher-order network of protein and RNA interactions.

Further reading: RNA Editing: Current Research and Future Trends

from Dong Li and Chuanbin Mao writing in Bionanotechnology: Biological Self-assembly and its Applications:

A variety of naturally occurring biological materials exhibits supramolecular self-assembly properties. By incorporation of signaling motifs, biological information and functional units, these biological materials can find extensive applications in developing nanotechnology, material science, tissue engineering and nanomedicine. In this review, some naturally occurring materials, which can be genetically engineered to display or chemically modified to incorporate foreign peptides, are summarized. The self-assembly behaviors of these biological materials generates hierarchically organized structures from the bottom up. The presentation of functional peptides on these biological materials enables the production of biomaterials for different applications. More and more naturally occurring biological materials are to be studied with the development of biotechnology and nanotechnology.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

from Jasna Rakonjac and James F. Conway writing in Bionanotechnology: Biological Self-assembly and its Applications:

Bacteriophage biology ushered in the era of modern molecular and structural biology. Accumulated wealth of knowledge on phage assembly, structure and the life cycle permitted their utilization in broad range of applications, from basic molecular biology to nanotechnology and pharmaceutical industry. This paper reviews current status of knowledge of bacteriophage assembly and structure represented by two morphologically different types, headed and filamentous bacteriophages. The principles of phage display are further presented, followed by a wide range of applications, including the most recent applications in nanotechnology.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

"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 Jared K. Raynes and Juliet A. Gerrard writing in Bionanotechnology: Biological Self-assembly and its Applications:

It is becoming increasingly clear that nature employs amyloid fibrils in a functional role for a range of processes, from immune responses, to aiding in the colonisation of bacteria. These functional amyloid fibrils have inspired researchers to investigate the potential of amyloid fibrils as novel bionanomaterials. The amyloid fibril structure possesses many features that make it an ideal candidate for use in bionanomaterials. These include: their nanometre size, which gives rise to a high surface-to-volume ratio enabling high loading capacities of decorations on their surface; the ability to self-assemble, which affords a bottom-up approach to material design; the potential to be manufactured from waste materials; and their diverse chemical functionality, arising from their amino acid composition, which allows for decoration with chemicals and biomolecules via amino acid moieties such as amino and sulfur groups. This review focuses on the assembly of amyloid fibrils and how these features are enabling their emerging uses as novel bionanomaterials.

Further reading: Bionanotechnology: Biological Self-assembly and its Applications

from Sara Tomaselli, Federica Galeano, Franco Locatelli and Angela Gallo writing in RNA Editing: Current Research and Future Trends:

All viruses that have dsRNA structures at any stages of their life cycle may potentially undergo RNA editing mediated by ADAR enzymes. Indeed, a number of reports describe A-to-I sequence changes in viral genomes and/or transcripts that are consistent with ADAR activity. These modifications can appear as either hyperediting during persistent viral infections or specific RNA editing events in viral dsRNAs. It is now well established that ADAR enzymes can affect virus interaction with their host in both an editing-dependent and -independent manner, with ADARs playing for both sides: the host and the virus. Despite the discovery of editing events on viral RNA dates back to thirty years ago, the biological consequences of A-to-I changes during viral infection is still far to be completely elucidated. In particular, the proviral role played by ADAR1, partly due to PKR inhibition, together with its antiviral effect following hyperediting events, put in evidence the complex role played by RNA editing in the regulation of viral infections and innate immune response.

Further reading: RNA Editing: Current Research and Future Trends

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)