from Christof Godts, Gitte Loozen, Marc Quirynen and Wim Teughels writing in Oral Microbial Ecology: Current Research and New Perspectives:

The human oral cavity is colonized by a wide variety of bacteria, which form very complex and dynamic biofilms on hard and soft tissues. Certain members of these microbiological communities are associated with oral infections, such as caries and periodontal diseases. New treatment approaches are emerging that do not rely on conventional antibiotic therapies, since complete eradication of pathogenic bacteria from oral biofilms is impossible and antibiotic resistance is becoming problematic. For example, attempts have been made to reduce the overall pathogenicity of tissue-associated biofilms by introducing live beneficial bacteria. Early successes, primarily in the field of gastro-intestinal microbiology, have paved the way for the introduction of probiotics in oral health care. These new anti-/pro-microbial therapies are considered very promising for prevention and treatment of plaque related oral diseases. In this review, the concept of probiotics for oral healthcare is introduced, followed by an overview of the diverse mechanisms of probiotic action in the oral cavity. Since the benefits of probiotics will ultimately be revealed by clinical studies, the clinical outcomes of probiotic applications for combating dental caries and periodontal diseases are addressed. Finally the interactions of probiotics with the oral microbial ecosystem are discussed and future perspectives regarding the oral probiotic concept are presented.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from George Hajishengallis writing in Oral Microbial Ecology: Current Research and New Perspectives:

The polymicrobial community that initiates periodontal disease does not represent a random compilation of bacteria. Rather, these bacteria form organized consortia that have evolved through mutually beneficial relationships. This review focuses on microbial immune subversion as a means by which select pathogens may contribute to the adaptive fitness of the entire periodontal biofilm. For instance, Porphyromonas gingivalis expresses specialized virulence traits that undermine immunity and promote non-resolving inflammation, which, respectively, protect the bacteria and facilitate nutrient acquisition. The virulence factors involved (e.g. cysteine proteases and atypical lipopolysaccharide structures) are released as components of readily diffusible membrane vesicles, which can thus become available for the benefit of other biofilm organisms. The elucidation of immune subversion mechanisms of key periopathogens that promote the collective virulence of their communities may provide new avenues of therapeutic intervention in human periodontitis.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from John G. Thomas writing in Oral Microbial Ecology: Current Research and New Perspectives:

The link between oral flora and lung infections in mechanically ventilated (MV) patients (the 'Oral Systemic Link') has always been circumstantial, based on clinical and nursing practices and preventative care. At the turn of the 20th century, that began to change as molecular and imaging methods provided tools to better evaluate microbial exchange, refocusing on the importance of the endotracheal tube (ETT) lumen as a potential conduit, devoid of normal cellular defensive components. We undertook the challenge in two phases, first engineering the Adult -Ventilator Endotracheal Lung (A-VEL) simulator to replicate the closed, bi-directional airway and stress of the intubated patient in the intensive care unit (ICU). Of singular importance, was the incorporation of multiple quantitative imaging techniques to define the 3-D biofilm luminal development in Stages (I-IV) from single to complex microbial communities and the incorporation of dental pathogens (Streptococcus mutans and Porphyromonas gingivalis) as an endogenous event, in the preconditioning of the ETT luminal surface, an abiotic medical device. The second phase shifted to the in vivo environment and in multiple clinical studies, unmasked the bi-phasic nature of ETT luminal colonization, oral-endogenous (Early) to systemic - exogenous (Late) at a 3-5 day 'switch'. Further, the ICU studies dramatized the shift from the infectious process in VAP to Work of Breathing (WOB), where the former occurred in 16%, while biofilm accretion, occlusion of the ETT lumen and increased airway resistance occurred in 100% of intubated patients. Most recently, we have used both 16S (microarray) and 18S rRNA (pyrosequencing) to redefine the proportions of bacteria and fungi from oral reservoirs, and been astonished by the richness and diversity of the oral fungal community in the ETT accretion occlusion, often yielding >15 species . Endotracheal Tube Associated Pneumonia (EAP) management continues to elude optimal strategies, but the use of selected oral probiotics coupled with better oral care in both the ICU and admitting institutions is gaining reinforcement: "Oral Stewardship". Further, the utilization of dental professionals in the ICU has importance, as has the recognition that the next fertile area of airway disease (oral to systemic) study is the neonatal intensive care unit (NICU), where 50% of newborns may be intubated and develop EAP with no teeth. How? Why?

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from Marieke P.T. Otten, Henk J. Busscher, Chris G. van Hoogmoed, Frank Abbas and Henny C. van der Mei writing in Oral Microbial Ecology: Current Research and New Perspectives:

An overview is presented on oral biofilm formation and recent developments in oral biofilm control using mechanical devices (manual or powered toothbrushes and interdental cleaning devices) and biofilm control based on oral chemotherapeutics (antibacterial toothpastes and mouthrinses). For clinical efficacy of oral chemotherapeutics, it is important that the antibacterial remains active in the oral cavity for periods longer than the actual brushing or rinsing time, a characteristic called 'substantivity'. Substantivity can be achieved by adsorption of antibacterials to oral hard and soft tissues followed by release. Mechanical cleaning never results in complete removal of oral biofilm: most notably in fissures, interproximal spaces, gingival pockets and around orthodontic appliances. Recently, it has been demonstrated that this residual biofilm can act as a reservoir for oral chemotherapeutics that are slowly released over time in bio-active concentrations. This function of oral biofilm was already known for fluoride and has been demonstrated to aid in preventing caries. Results from our laboratory showed that residual biofilm after mechanical cleaning can release absorbed antibacterial agents from toothpastes and mouthrinses in bio-active concentrations.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from Michael F. Cole, Katherine A. Wirth and George H. Bowden writing in Oral Microbial Ecology: Current Research and New Perspectives:

In this review we consider the biology of the viridans streptococci in the human oropharynx with a particular focus on the pioneer bacterium Streptococcus mitis. We show that, although this species is a constant component of the human oral cavity, each person harbors a unique and diverse population of stains that appear not to be shared within a family and, apparently, are rarely transmitted from mother to neonate. The population of stains of S. mitis within the mouth of each individual exhibits turnover perhaps in response to pressure exerted by the mucosal immune system since it has been shown that some secretory immunoglobulin A (SIgA) antibodies are clone-specific. We assert that the strains that are successful in establishing in the mouth are physiologically adapted to occupy their niche within their habitat. While it is clear that in vitro experiments and animal models have provided useful information, they are no substitute for studying commensal oral bacteria in their environment, the human oral cavity.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from Saswat Sourav Mohapatra and Indranil Biswas writing in Oral Microbial Ecology: Current Research and New Perspectives:

The human oral cavity is estimated to host more than 700 bacterial species formed into distinct biofilm communities, of which more than 50% are yet to be cultured in the laboratory. Though oral streptococci constitute two thirds of the total commensals, only a fraction known as mutans streptococci are involved in producing dental caries. The oral streptococci are the primary colonizers of the tooth and other mucosal surfaces in the oral cavity and initiate plaque biofilm formation. Mutual interaction in the form of cooperation and competition shapes the constitution of the oral microflora. Colonization by Streptococcus mutans, having significant acidogenicity and aciduricity properties, is primarily responsible for dental caries formation. Recent advances in nucleotide sequencing and other high throughput methods have provided significant clues to the biology and gene regulation of S. mutans in a community structure. Many therapeutic methods are being devised to specifically target the S. mutans in the biofilm, without disturbing other bacterial species. Significant among them are targeting the interbacterial signaling, replacing cariogenic flora with non-cariogenic flora, and specifically targeted antimicrobial peptides (STAMPs). As the research progresses in this field, better therapeutic methods are on the horizon.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from Nicholas S. Jakubovics writing in Oral Microbial Ecology: Current Research and New Perspectives:

A core component of microbial biofilms is the extracellular matrix, which binds together the assembled micro-organisms and regulates the passage of small molecules to and from cells. The scaffolding of the matrix is composed of biological macromolecules including carbohydrates, nucleic acids and proteins. The production and function of extracellular polysaccharides in oral biofilms has been the subject of a great deal of research over many decades, and is considered in a separate review. More recently, it has become clear that proteins and extracellular DNA (eDNA) play key roles in maintaining the structure of many different biofilms, including oral biofilms. This paper reviews the recent research on proteins and eDNA in the biofilm matrix, and discusses the evidence that oral micro-organisms utilise these macromolecules for specific functions within mixed-species biofilms.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from Justin Merritt and Jens Kreth writing in Oral Microbial Ecology: Current Research and New Perspectives:

Oral streptococci encounter an exceptionally wide range of environmental stresses and population densities. These stimuli are sensed by efficient detection systems that also coordinate the appropriate adaptive genetic responses. The majority of these detection systems utilize membrane bound sensory proteins that are directly or indirectly regulated by their sensed stimuli. Such systems play an intimate role in mitigating the potential damage caused by changes in redox potential, fluctuations in local pH, and toxicity from antimicrobial agents. In addition, the typical life cycle of oral streptococci includes a transition from growth in a relatively low cell density planktonic state to an extremely high cell density biofilm environment. Consequently, various sensory systems are dedicated to detecting this increase in population density and regulating the genetic pathways that are essential for persistence in a highly competitive multispecies biofilm environment. Recent studies have identified many of the targets of these sensory systems and have provided unprecedented insight into the intimate connection between the constantly changing oral environment and the genetic machinery of oral bacteria.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from William Wade writing in Oral Microbial Ecology: Current Research and New Perspectives:

The oral microbiota is highly diverse and includes fungi, protozoa, viruses and bacteria. Both domains of prokaryotes, Archaea and Bacteria are present. Representatives of the Archaea are restricted to a few taxa in the genus Methanobrevibacter, while there are over 600 species of Bacteria, from at least 12 phyla. The full diversity of bacterial populations in the mouth has been recognised following the application of culture-independent methods of analysis, based on 16S rRNA gene sequence comparisons. Because oral bacteria are typically slow-growing and fastidious, and around half cannot be grown in the laboratory at all, the taxonomic process of classifying and naming bacterial species is ongoing and over 100 cultivable taxa have still to be named. In recent years, attempts have been made to culture the not-yet-cultured portion of the microbiota. There are a number of reasons why certain taxa are uncultivable and these include a need for a specific nutrient, extreme oxygen sensitivity and dependence on other organisms. The inter-dependence among members of the oral microbial community may relate to cooperative degradation of natural substrates for growth or the need to participate in signalling networks that control growth rate and resuscitation from dormancy. Novel culture media and methods are being developed that reproduce the in vivo environment and thus encourage previously uncultured organisms to grow in the laboratory.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from Purnima S Kumar, Matthew R Mason and Janel Yu writing in Oral Microbial Ecology: Current Research and New Perspectives:

Dental plaque biofilm is composed of a diverse microbial community. Several decades of research have been focused on the role played by the subgingival biofilm in the etiology of periodontal diseases. However, recent evidence from other ecosystems within the human body indicates that these biofilms also play an important role in maintaining health. The purpose of this review is to explore the health benefits of subgingival plaque, and to outline the development of the biofilm as well as to characterize the bacteria present in the plaque biofilm in health and disease. Additionally, the virulence mechanisms of health and disease-associated biofilms will be outlined.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

from David Beighton, Sadaf Rasheed Mughal and Thuy Do writing in Oral Microbial Ecology: Current Research and New Perspectives:

The oral biofilm proliferates in the mouth by primarily utilizing components of saliva as dietary foods are rapidly cleared. The complex microbial community functions in a concerted manner to obtain nutrients, sugars and amino acids, from salivary components including mucins, by the production of a range of glycosidic enzymes including sialidase, β-galactosidase, N-acetylglucosaminidases, α-fucosidase and mannosidases and exo- and endo-proteolytic activities. Degradation of glycans occurs sequentially and in vitro studies indicate that liberated sugars are rapidly transported though evidence of cross-feeding between species, utilizing liberated sugars, is evident. Streptococcus oralis is a species with the greatest ability to deglycosylate both N- and O-linked glycans and has been used extensively in model systems. New research should take advantage of modern high throughput sequencing techniques to determine the biofilm transcriptome of humans receiving defined diet, including fasting, to ascertain the response of the biofilm to in vivo conditions.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

"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 Alexander H. Rickard, Adam J. Underwood and William Nance writing in Oral Microbial Ecology: Current Research and New Perspectives:

Mature dental-plaque biofilm communities contain hundreds of bacterial species. The potential for these communities to cause caries or periodontal disease relates to bacterial spatiotemporal biofilm development and species composition. At least three forms of inter-species interactions can conceivably mediate altered biofilm development and species composition. These are coaggregation, metabolic interactions, and cell-cell signaling. Coaggregation is the specific recognition and adhesion of different species of bacteria and likely contributes toward the ordered (sequential) integration of species into biofilms as well as improving species retention in a flowing environment. 'Metabolic interactions' is an umbrella term that describes the exchange of metabolites or environmental protection afforded between adjacent species within dental plaque. Cell-cell signaling is a phenomenon that has gained increasing research interest over the past decade. One broad inter-species signaling molecule system consists of a collection of inter-convertible cell-cell signal molecules that are collectively called autoinducer-2 (AI-2). Evidence indicates that AI-2 can alter bacterial phenotypes, when present in saliva at concentrations as low as the nanomolar range. It is the aim of this review to describe each of these inter-species phenomena, with case-examples, and extrapolate singular and combined roles in the spatio-temporal development of dental plaque. The potential for these phenomena to create shifts in community species composition have implications for the development of polymicrobial diseases.

Further reading: Oral Microbial Ecology: Current Research and New Perspectives

"the book comprises 11 papers addressing different applications of biofilm research ... each paper provides a useful update/review of a given area - I particularly like the interactions described in the quorum sensing paper." from Joanna Verran, Manchester Metropolitan University, UK writing in Microbiology Today (2012) read more ...

Microbial Biofilms: Current Research and Applications Edited by: Gavin Lear and Gillian D. Lewis ISBN: 978-1-904455-96-7 Publisher: Caister Academic Press Publication Date: February 2012 Cover: hardback "a useful update" Micro. Today

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 Anna M. Romaní, Joan Artigas and Irene Ylla writing in Microbial Biofilms: Current Research and Applications:

Biofilms in aquatic ecosystems colonize various compartments (sand, rocks, leaves) and play a key role in the uptake of inorganic and organic nutrients. Due to their extracellular enzyme capabilities, biofilm microorganisms are able to use organic matter from the surrounding water and increasing activities are related to the availability of biodegradable organic carbon. The most common extracellular enzymes analysed are those involved in the decomposition of polysaccharides, peptides and organic phosphorus compounds, and changes in enzyme expression have been related to the use of different sources of organic matter available in the ecosystem (i.e., during drought-storm and/or pollution episodes). Enzymes important for microbial acquisition of nitrogen and phosphorus also respond to nutrient content and/or imbalances in the flowing water. Additionally, biofilm extracellular enzyme activities are modified by the internal recycling of organic matter and microbial interactions (competition/synergism) within the biofilm, such as algal-bacterial and fungal-bacterial interactions. Although an extensive knowledge of the biofilm structure is required for the interpretation of extracellular enzyme activities in aquatic biofilms, they give a very useful, integrative measure of the biofilm community function in relation to organic matter use and cycling.

Further reading: Microbial Biofilms: Current Research and Applications

"Highly recommended is the chapter on interactions between plants and biofilms" from Hans-Curt Flemming (Duisburg, Germany) writing in Biospektrum (2012) 18: 109. read more ...

Microbial Biofilms: Current Research and Applications Edited by: Gavin Lear and Gillian D. Lewis ISBN: 978-1-904455-96-7 Publisher: Caister Academic Press Publication Date: February 2012 Cover: hardback "Highly recommended" (Biospektrum)

from Koichi Nishio, Atsushi Kouzuma, Souichiro Kato and Kazuya Watanabe writing in Microbial Biofilms: Current Research and Applications:

Microbial fuel cells (MFCs) are devices that exploit microbial catabolic activities to generate electricity from a variety of starting materials, including complex organic waste and renewable biomass. The use of these energy sources provides MFCs with a great advantage over chemical fuel cells that utilize only purified reactive fuels (e.g., hydrogen). In an MFC bioreactor, microbes that respire using an anode with organics as electron donors grow preferentially, resulting in accelerated and increased current generation with time. The placement of an anode in either soil or sediment represents a simplified MFC system, known as a sediment MFC, which generates current as soil microbes utilize the anode as an electron acceptor. In addition, the irradiation of an MFC system results in the proliferation of photosynthetic microbes together with anode-respiring microbes, resulting in the syntrophic conversion of light energy into electricity. These examples demonstrate that the MFC system is based on a variety of fundamental and sustainable bioenergy processes, and we suggest that a deeper understanding of how microbes transfer electrons to anodes is essential for further developments of MFC systems.

Further reading: Microbial Biofilms: Current Research and Applications

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 Steve Flint and Gideon Wolfaardt writing in Microbial Biofilms: Current Research and Applications:

Biofilms can directly or indirectly be attributed to deterioration of the underlying substratum. Corrosion may result, particularly if the surface comprises metal or metal alloy. This phenomenon, referred to as microbially influenced corrosion (MIC) affects many industries from food manufacture to medicine. The economic impact of corrosion is significant due to the need for replacing corroded equipment, repairs and attempts to prevent corrosion. MIC is believed to be responsible for one third of all metallic corrosion. Although there have been many studies into the mechanisms of MIC, the process is relatively poorly understood. Most information relates to pure cultures, however biofilms are rarely composed of single species thus most models are a simplification of the real process. It is likely the MIC depends on the composition of the biofilm and the environment surrounding the biofilm. Prevention and control methods rely on mechanical cleaning of fouling and chemical removal and killing of biofilms. Future control measures are likely to focus on preventing biofilm formation.

Further reading: Microbial Biofilms: Current Research and Applications

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 Rainer Gross, Andreas Schmid and Katja Buehler writing in Microbial Biofilms: Current Research and Applications:

Biofilms are mainly known for causing problems in medical and industrial settings due to their persistence towards treatment with bactericides, including antibiotics. However, in the area of bioremediation they are widely recognized for their ability to degrade hazardous or organic compounds to CO₂ and biomass. Biofilms represent a highly interesting biological concept since they unite important characteristics such as the ability of self-immobilization and increased robustness to various physical, chemical and biological stressors, which make them exceedingly attractive for productive catalysis. The following review provides a detailed survey of biofilm applications for productive biocatalysis on lab-, pilot-, and industrial scales, regarding fermentation as well as biotransformation reactions. It discusses technological as well as biological challenges of biofilm driven catalysis, presenting developments in the field of biofilm reactor technology and the latest findings in understanding biofilm dynamics. Biocatalysis related issues like genetic stability, evolution, uncontrolled growth as well as detachment, contamination risks, monitoring of biomass, EPS, chemical and biological heterogeneity are considered.

Further reading: Microbial Biofilms: Current Research and Applications

from Gabriele Pastorella, Giulio Gazzola, Seratna Guadarrama and Enrico Marsili writing in Microbial Biofilms: Current Research and Applications:

Bioremediation uses microorganisms to remove, detoxify, or immobilize pollutants, and does not require addition of harmful chemicals. Bioremediation is particularly suitable for large areas where contaminant concentrations are relatively low and the hydrology of the soil does not support an aggressive chemical remediation strategy. In the last few years, researchers have described the mechanisms of bioremediation for numerous priority pollutants, including chlorinated hydrocarbons, polyaromatic hydrocarbons, and heavy metals. However, most studies published to date have dealt with planktonic cultures grown under controlled laboratory conditions. Microorganisms in the environment occur mostly as biofilms, whose development is encouraged by the presence of solid surfaces and the limited amounts of organic carbon. Therefore, optimization of bioremediation processes in the field requires a thorough knowledge of biofilm structure, dynamic, and interaction with pollutants and other environmental factors. In this chapter, we describe the recent advances in bioremediation, with particular regard to the role of microbial biofilms. We discuss emerging technologies, such as bioelectroremediation and microbially produced surfactants. We also show how genetic engineering technologies may be employed to improve bioremediation effectiveness, both in laboratory and in field applications.

Further reading: Microbial Biofilms: Current Research and Applications

from G.A. Clark Ehlers and Susan J. Turner writing in Microbial Biofilms: Current Research and Applications:

Biofilms occur frequently inside various engineered systems for wastewater treatment. These include traditional trickling filter systems, modified lagoons, and specialized supplementary systems for nutrient removal or treatment of specialized wastes. The major advantages of biofilm systems over suspension treatment is the high microbial density that can be achieved, leading to smaller treatment system footprints, and the inherent development of aerobic, anoxic and anaerobic zones which enable simultaneous biological nutrient removal. The intrinsic resistance of biofilm communities to changing environmental conditions creates the added advantage that biofilm-based treatment systems are more resilient to influent variation in toxicity and nutrient concentrations. In contrast to biofilms of environmental or biomedical relevance comparatively little is known about development and stability in waste treatment systems. The advent of tools that enable the study of biofilms in reactor systems on a molecular level has enabled greater insight into the physiologically and biochemically relevant pathways that may facilitate optimized processes. In this chapter, the current literature on biofilms in wastewater treatment systems is reviewed and opportunities for further development in this field are identified.

Further reading: Microbial Biofilms: Current Research and Applications

from Gavin Lear, Andrew Dopheide, Pierre-Yves Ancion, Kelly Roberts, Vidya Washington, Jo Smith and Gillian D. Lewis writing in Microbial Biofilms: Current Research and Applications:

This chapter reviews our current understanding of the roles biofilm-associated microbial communities play in both maintaining and improving the ecological health of freshwater rivers and streams. Biofilms are where most of the bacteria present in freshwater systems are found, and have been identified as major sites for primary production, carbon and nutrient cycling. Advances in various scientific methodologies have recently been used to characterise the enormous diversity of biofilms, in terms of their structural, chemical and biological traits. The microbial life present within most natural biofilms, as well as associated exudates and lysates have been identified as a valuable, nutrient rich food source for a variety of benthic consumers. Furthermore, the diverse metabolic potential of these complex communities, in combination with various protective traits offered by the biofilm 'mode-of-life', provide biofilms with an excellent ability to degrade, or otherwise transform a vast array of freshwater pollutants. Despite this apparent resilience, we highlight the sensitivity of these poorly studied freshwater biofilm communities to various human activities, and consider their potential as a reliable and sensitive biological indicator of freshwater ecological health.

Further reading: Microbial Biofilms: Current Research and Applications

from James D. Bryers writing in Microbial Biofilms: Current Research and Applications:

Clinically related research on biofilms has expanded exponentially in the past ten years due to the pandemic of nosocomial (hospital-related) infections. Biofilms are thought to cause a significant amount of all human microbial infections, according to the Centers for Disease Control and Prevention. Nosocomial infections are the fifth leading cause of death in the U.S. with more than two million cases annually (or approximately 10% of American hospital patients). The difficulty of eradicating biofilm bacteria with classic systemic antibiotic treatments is a prime concern of medicine. Biofilm bacteria can be up to a thousand times less susceptible to antimicrobial stress than their freely suspended counterparts. This chapter discusses the pathogenesis of a number of biofilm-mediated infections, including: oral infections, biomedical device based infections, osteomyelitis, otitis media, and others. Emerging research in biofilm control and prevention is also reviewed.

Further reading: Microbial Biofilms: Current Research and Applications

from Mette Burmølle, Annelise Kjøller and Søren J. Sørensen writing in Microbial Biofilms: Current Research and Applications:

Biofilms in soil are composed of multiple species microbial consortia attached to soil particles and biotic surfaces including roots, fungal hyphae and decomposing organic material. The bacteria present in these biofilms gain several advantages including protection from predation, desiccation and exposure to antibacterial substances, and optimized acquisition of nutrients released in the mycosphere. Studies of soil biofilms are complicated by the composite structure of the soil environment; therefore, various simplified model systems have been applied to study succession and bacterial interactions in soil biofilms. Model system observations indicate an increased efficiency to degrade and decompose organic material and xenobiotic compounds by these multispecies bacterial communities. Consequently, soil biofilms may be valuable tools for bioremediation and biocontrol. However, soil biofilms may also provide survival sites for opportunistic pathogenic bacteria, providing enhanced protection and increasing their potential to survive and evolve in the soil environment. In this review, we provide evidence that biofilms are of major importance for the fitness of individual bacteria and the wider soil ecology, due to the accumulated selective advantage provided to bacteria by the biofilm mode-of-life.

Further reading: Microbial Biofilms: Current Research and Applications

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 Robert J. Goldstone, Roman Popat, Matthew P. Fletcher, Shanika A. Crusz and Stephen P. Diggle writing in Microbial Biofilms: Current Research and Applications:

It is now well recognised that populations of bacteria from many Gram-positive and Gram-negative species cooperate and communicate to perform diverse social behaviours including swarming, toxin production and biofilm formation. Communication between bacterial cells involves the production and detection of diffusible signal molecules and has become commonly known as quorum sensing (QS). In addition, an evolutionary perspective on QS illuminates important phenomena which help in understanding the prevalence and diversity of QS phenotypes and strategies under various conditions. The research fields of QS and biofilm formation often overlap with a number of studies demonstrating that QS is an important regulatory mechanism of biofilm formation in a variety of bacterial species. However in contrast, there are conflicting reports, demonstrating that QS appears to play a minimal role in the development of biofilms. Our aim in this review is to highlight the key findings with respect to QS and the subsequent impact on biofilm formation. We also discuss QS and cooperation in the context of social evolution and how this may impact on the development and maintenance of microbial biofilms.

Further reading: Microbial Biofilms: Current Research and Applications

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 Venkatachalam Lakshmanan, Amutha Sampath Kumar and Harsh P. Bais writing in Microbial Biofilms: Current Research and Applications:

Microorganisms have historically been studied as planktonic or free-swimming cells, but most exist as sessile communities attached to surfaces, in multicellular assemblies known as biofilms. In the process of coping with both the pathogenic and beneficial interactions, the rhizosphere of plant roots encourages formation of sessile communities that begins with the attachment of free-floating microorganisms to a surface. Certain bacteria such as plant growth promoting rhizobacteria not only induce plant growth but also protect plants from soil-borne pathogens in a process known as biocontrol. Contrastingly, other rhizobacteria in a biofilm matrix may cause pathogenesis in plants. Although research suggests that biofilm formation on plants is associated with biological control and pathogenic response, little is known about how plants regulate this association. The scope of this chapter is restricted to biofilm-forming bacteria and their interactions with terrestrial plants, specifically emphasizing recent work. After an overview of documented interactions between bacteria and plant tissues, we examine some of the more prominent mechanisms of biofilm formation on and around plant surfaces.

Further reading: Microbial Biofilms: Current Research and Applications

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)