Giant viruses come of age.
Abstract Viruses with genomes up to a few megabases in length are a common occurrence in nature, even though they have escaped our notice until recently. These giant viruses infect mainly single-celled eukaryotes and isolation efforts concentrating on amoebal hosts alone have spawned hundreds of viral isolates, featuring viruses with previously unseen virion morphologies and the largest known viral genomes and particles. One of the challenges that lie ahead is to analyze and categorize the available data and to establish an approved classification system that reflects the evolutionary relationships and biological ...
Source: Current Opinion in Microbiology - March 18, 2016 Category: Microbiology Authors: Fischer MG Tags: Curr Opin Microbiol Source Type: research

Protein homeostasis-more than resisting a hot bath.
mling U Abstract Maintenance of protein homeostasis is essential for survival of all organisms. In bacteria, the protein quality control system has a broad physiological impact beyond heat shock resistance, being involved in virulence, antibiotic resistance, as well as protection against environmental stresses. Its contribution to rejuvenation and growth arrest suggests interference with protein quality control to be a novel antimicrobial strategy. Remarkably, a protein quality control module originating from environmental strains has been found to be horizontally transferred to predominant clonal groups of bacter...
Source: Current Opinion in Microbiology - March 11, 2016 Category: Microbiology Authors: Lee C, Wigren E, Lünsdorf H, Römling U Tags: Curr Opin Microbiol Source Type: research

Sensational biofilms: surface sensing in bacteria.
Abstract The first step in the development of a bacterial biofilm is contact with the surface on which the microbe will form this community. We review recent progress on 'surface sensing', and engage the question of 'how does a microbe know it is on a surface?' PMID: 26968016 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - March 8, 2016 Category: Microbiology Authors: O'Toole GA, Wong GC Tags: Curr Opin Microbiol Source Type: research

Editorial overview: Cell regulation: Amazingly sophisticated regulatory processes in bacteria!
g U PMID: 26965103 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - March 7, 2016 Category: Microbiology Authors: Felden B, Römling U Tags: Curr Opin Microbiol Source Type: research

Hfq: the flexible RNA matchmaker.
Abstract The RNA chaperone protein Hfq is critical to the function of small, base pairing RNAs in many bacteria. In the past few years, structures and modeling of wild type Hfq and assays of various mutants have documented that the homohexameric Hfq ring can contact RNA at four sites (proximal face, distal face, rim and C-terminal tail) and that different RNAs bind to these sites in various configurations. These studies together with novel in vitro and in vivo experimental approaches are beginning to give mechanistic insights into how Hfq acts to promote small RNA-mRNA pairing and indicate that flexibility is inte...
Source: Current Opinion in Microbiology - February 20, 2016 Category: Microbiology Authors: Updegrove TB, Zhang A, Storz G Tags: Curr Opin Microbiol Source Type: research

Bacillus subtilis extracytoplasmic function (ECF) sigma factors and defense of the cell envelope.
Abstract Bacillus subtilis provides a model for investigation of the bacterial cell envelope, the first line of defense against environmental threats. Extracytoplasmic function (ECF) sigma factors activate genes that confer resistance to agents that threaten the integrity of the envelope. Although their individual regulons overlap, σ(W) is most closely associated with membrane-active agents, σ(X) with cationic antimicrobial peptide resistance, and σ(V) with resistance to lysozyme. Here, I highlight the role of the σ(M) regulon, which is strongly induced by conditions that impair peptidoglyc...
Source: Current Opinion in Microbiology - February 19, 2016 Category: Microbiology Authors: Helmann JD Tags: Curr Opin Microbiol Source Type: research

Giant viruses and the origin of modern eukaryotes.
a M Abstract Several authors have suggested that viruses from the NucleoCytoplasmic Large DNA Viruses group (NCLDV) have played an important role in the origin of modern eukaryotes. Notably, the viral eukaryogenesis theory posits that the nucleus originated from an ancient NCLDV-related virus. Focusing on the viral factory instead of the virion adds credit to this hypothesis, but also suggests alternative scenarios. Beside a role in the emergence of the nucleus, ancient NCLDV may have provided new genes and/or chromosomes to the proto-eukaryotic lineage. Phylogenetic analyses suggest that NCLDV informational prote...
Source: Current Opinion in Microbiology - February 16, 2016 Category: Microbiology Authors: Forterre P, Gaïa M Tags: Curr Opin Microbiol Source Type: research

The Xanthomonas type IV pilus.
Abstract Type IV pili, a special class of bacterial surface filaments, are key behavioral mediators for many important human pathogens. However, we know very little about the role of these structures in the lifestyles of plant-associated bacteria. Over the past few years, several groups studying the extensive genus of Xanthomonas spp. have gained insights into the roles of played by type IV pili in bacteria-host interactions and pathogenesis, motility, biofilm formation, and interactions with bacteriophages. Protein-protein interaction studies have identified T4P regulators and these, along with structural studies...
Source: Current Opinion in Microbiology - February 11, 2016 Category: Microbiology Authors: Dunger G, Llontop E, Guzzo CR, Farah CS Tags: Curr Opin Microbiol Source Type: research

Linking bacterial type I toxins with their actions.
Abstract Bacterial type I toxin-antitoxin systems consist of stable toxin-encoding mRNAs whose expression is counteracted by unstable RNA antitoxins. Accumulating evidence suggests that these players belong to broad regulatory networks influencing overall bacterial physiology. The majority of known transmembrane type I toxic peptides have conserved structural characteristics. However, recent studies demonstrated that their mechanisms of toxicity are diverse and complex. To better assess the current state of the art, type I toxins can be grouped into two classes according to their location and mechanisms of action:...
Source: Current Opinion in Microbiology - February 11, 2016 Category: Microbiology Authors: Brielle R, Pinel-Marie ML, Felden B Tags: Curr Opin Microbiol Source Type: research

Survival games at the dinner table: regulation of Enterobacterial virulence through nutrient sensing and acquisition.
Abstract The ability of bacterial pathogens to colonize specific host niches is largely dependent on acquisition of essential metabolites and co-factors for growth and sensing and adapting in response to specific environmental cues. Nutrient availability in host environments is strongly influenced by host physiology and immunity, diet, and competition with other members of the host microbiota. Rapid adaptation to environmental cues and nutrient availability is a hallmark of bacterial fitness and virulence. This adaptability requires complex regulatory networks that tightly link sensing of nutrient availability to ...
Source: Current Opinion in Microbiology - February 9, 2016 Category: Microbiology Authors: Porcheron G, Schouler C, Dozois CM Tags: Curr Opin Microbiol Source Type: research

Cell cycle control in Alphaproteobacteria.
Abstract Alphaproteobacteria include many medically and environmentally important organisms. Despite the diversity of their niches and lifestyles, from free-living to host-associated, they usually rely on very similar mechanisms to control their cell cycles. Studies on Caulobacter crescentus still lay the foundation for understanding the molecular details of pathways regulating DNA replication and cell division and coordinating these two processes with other events of the cell cycle. This review highlights recent discoveries on the regulation and the mode of action of conserved global regulators and small molecule...
Source: Current Opinion in Microbiology - February 9, 2016 Category: Microbiology Authors: Collier J Tags: Curr Opin Microbiol Source Type: research

Cyclic (di)nucleotides: the common language shared by microbe and host.
Abstract Fluency in a common language allows individuals to convey information and carry out complex activities that otherwise would be difficult or even impossible without the benefit of shared communication. Cyclic (di)nucleotides have recently been recognized as such an accessible language understood by both microbe and the host, ever since remarkable progresses have revealed the molecular details of these nucleotide second messengers used in cellular communication systems. Though undergoing separate evolutionary pathways in prokaryotes and eukaryotes, cyclic (di)nucleotides enable microbes to influence host ce...
Source: Current Opinion in Microbiology - February 4, 2016 Category: Microbiology Authors: Gao J, Tao J, Liang W, Jiang Z Tags: Curr Opin Microbiol Source Type: research

Viral metagenomics: are we missing the giants?
Abstract Amoeba-infecting giant viruses are recently discovered viruses that have been isolated from diverse environments all around the world. In parallel to isolation efforts, metagenomics confirmed their worldwide distribution from a broad range of environmental and host-associated samples, including humans, depicting them as a major component of eukaryotic viruses in nature and a possible resident of the human/animal virome whose role is still unclear. Nevertheless, metagenomics data about amoeba-infecting giant viruses still remain scarce, mainly because of methodological limitations. Efforts should be pursue...
Source: Current Opinion in Microbiology - February 3, 2016 Category: Microbiology Authors: Halary S, Temmam S, Raoult D, Desnues C Tags: Curr Opin Microbiol Source Type: research

Self-synthesizing transposons: unexpected key players in the evolution of viruses and defense systems.
Abstract Self-synthesizing transposons are the largest known transposable elements that encode their own DNA polymerases (DNAP). The Polinton/Maverick family of self-synthesizing transposons is widespread in eukaryotes and abundant in the genomes of some protists. In addition to the DNAP and a retrovirus-like integrase, most of the polintons encode homologs of the major and minor jelly-roll capsid proteins, DNA-packaging ATPase and capsid maturation protease. Therefore, polintons are predicted to alternate between the transposon and viral lifestyles although virion formation remains to be demonstrated. Polintons a...
Source: Current Opinion in Microbiology - January 30, 2016 Category: Microbiology Authors: Krupovic M, Koonin EV Tags: Curr Opin Microbiol Source Type: research

Mimivirus inaugurated in the 21st century the beginning of a reclassification of viruses.
Abstract Mimivirus and other giant viruses are visible by light microscopy and bona fide microbes that differ from other viruses and from cells that have a ribosome. They can be defined by: giant virion and genome sizes; their complexity, with the presence of DNA and mRNAs and dozens or hundreds of proteins in virions; the presence of translation-associated components; a mobilome including (pro)virophages (and a defence mechanism, named MIMIVIRE, against them) and transpovirons; their monophyly; the presence of the most archaic protein motifs they share with cellular organisms but not other viruses; a broader host...
Source: Current Opinion in Microbiology - January 29, 2016 Category: Microbiology Authors: Sharma V, Colson P, Pontarotti P, Raoult D Tags: Curr Opin Microbiol Source Type: research

Escaping the biofilm in more than one way: desorption, detachment or dispersion.
Abstract Biofilm bacteria have developed escape strategies to avoid stresses associated with biofilm growth, respond to changing environmental conditions, and disseminate to new locations. An ever-expanding body of research suggests that cellular release from biofilms is distinct from a simple reversal of attachment and reversion to a planktonic mode of growth, with biofilm dispersion involving sensing of specific cues, regulatory signal transduction, and consequent physiological alterations. However, dispersion is only one of many ways to escape the biofilm mode of growth. The present review is aimed at distingui...
Source: Current Opinion in Microbiology - January 28, 2016 Category: Microbiology Authors: Petrova OE, Sauer K Tags: Curr Opin Microbiol Source Type: research

Acanthamoeba and mimivirus interactions: the role of amoebal encystment and the expansion of the 'Cheshire Cat' theory.
;o JS Abstract Acanthamoeba are natural hosts for giant viruses and their life cycle comprises two stages: a trophozoite and a cryptobiotic cyst. Encystment involves a massive turnover of cellular components under molecular regulation. Giant viruses are able to infect only the trophozoite, while cysts are resistant to infection. Otherwise, upon infection, mimiviruses are able to prevent encystment. This review highlights the important points of Acanthamoeba and giant virus interactions regarding the encystment process. The existence of an acanthamoebal non-permissive cell for Acanthamoeba polyphaga mimivirus, the ...
Source: Current Opinion in Microbiology - January 25, 2016 Category: Microbiology Authors: Silva LK, Boratto PV, La Scola B, Bonjardim CA, Abrahão JS Tags: Curr Opin Microbiol Source Type: research

RNA helicases in bacteria.
Abstract RNA plays a crucial role in the control of bacterial gene expression, either as carrier of information or as positive or negative regulators. Moreover, the machinery to decode the information, the ribosome, is a large ribonucleoprotein complex composed of rRNAs and many proteins. RNAs are normally single stranded but have the propensity to fold into secondary structures or anneal each other. In some instances these interactions are beneficial for the function of the RNA, but in other cases they may be deleterious. All cells have therefore developed proteins that act as chaperones or helicases to keep RNA ...
Source: Current Opinion in Microbiology - January 22, 2016 Category: Microbiology Authors: Khemici V, Linder P Tags: Curr Opin Microbiol Source Type: research

Emerging roles of RNA modifications in bacteria.
Abstract RNA modifications are known to abound in stable tRNA and rRNA, where they cluster around functionally important regions. However, RNA-seq based techniques profiling entire transcriptomes are now uncovering an abundance of modified ribonucleotides in mRNAs and noncoding RNAs, too. While most of the recent progress in understanding the regulatory influence of these new RNA modifications stems from eukaryotes, there is growing evidence in bacteria for modified nucleotides beyond the stable RNA species, including modifications of small regulatory RNAs. Given their small genome size, good genetic tractability,...
Source: Current Opinion in Microbiology - January 21, 2016 Category: Microbiology Authors: Marbaniang CN, Vogel J Tags: Curr Opin Microbiol Source Type: research

Intracellular replication of the well-armed pathogen Burkholderia pseudomallei.
Abstract The Burkholderia genus contains a group of soil-dwelling Gram-negative organisms that are prevalent in warm and humid climates. Two species in particular are able to cause disease in animals, B. mallei primarily infects Equus spp. and B. pseudomallei (BPS), that is able to cause potentially life-threatening disease in humans. BPS is naturally resistant to many antibiotics and there is no vaccine available. Although not a specialised human pathogen, BPS possesses a large genome and many virulence traits that allow it to adapt and survive very successfully in the human host. Key to this survival is the abil...
Source: Current Opinion in Microbiology - January 21, 2016 Category: Microbiology Authors: Willcocks SJ, Denman CC, Atkins HS, Wren BW Tags: Curr Opin Microbiol Source Type: research

Cap-like structures in bacterial RNA and epitranscriptomic modification.
Frindert J Abstract The absence of capped RNA is considered as a hallmark of prokaryotic gene expression. Recent developments combine next-generation sequencing with a chemo-enzymatic capture step that allows the enrichment of rare 5'-modified RNA from bacteria. This approach identified covalent cap-like linkage of a specific set of small RNAs to the ubiquitous redox cofactor NAD, and a profound influence of this modification on RNA turnover. The modification revealed an unexpected connection between redox biology and RNA processing. We discuss possible roles of the NAD modification as well as broader implication...
Source: Current Opinion in Microbiology - January 15, 2016 Category: Microbiology Authors: Jäschke A, Höfer K, Nübel G, Frindert J Tags: Curr Opin Microbiol Source Type: research

Exploiting the commons: cyclic diguanylate regulation of bacterial exopolysaccharide production.
án J Abstract Nowadays, there is increasing interest for bacterial polysaccharides in a wide variety of industrial sectors. This is due to their chemical and reological properties, and also the possibility to be obtained by fermentation processes. Biosynthesis of a growing number of exopolysaccharides (EPS) has been reported to be regulated by the ubiquitous second messenger c-di-GMP in a limited number of bacterial species. Since most bacteria are yet unexplored, it is likely that an unsuspected number and variety of EPS structures activated by c-di-GMP await to be uncovered. In the search of new EPS, mani...
Source: Current Opinion in Microbiology - January 13, 2016 Category: Microbiology Authors: Pérez-Mendoza D, Sanjuán J Tags: Curr Opin Microbiol Source Type: research

Fresh layers of RNA-mediated regulation in Gram-positive bacteria.
Abstract Bacterial regulatory RNAs have been defined as diverse classes of cis and trans elements that may intervene at each step of gene expression, from RNA and protein synthesis to degradation. Here, we report on a few examples from Gram-positive bacteria that extend the definition of regulatory RNAs to include 5' and 3' UTRs that also act as cis and trans regulators. New examples unveil the existence of cis and trans acting regulatory RNAs on a single molecule. Also, we highlight data showing that a key RNA chaperone in Enterobacteriaceae, Hfq, does not fulfill the same role in Gram-positive Firmicutes. P...
Source: Current Opinion in Microbiology - January 12, 2016 Category: Microbiology Authors: Bouloc P, Repoila F Tags: Curr Opin Microbiol Source Type: research

Too much of a good thing: regulated depletion of c-di-AMP in the bacterial cytoplasm.
Abstract Bacteria that synthesize c-di-AMP also encode several mechanisms for controlling c-di-AMP levels within the cytoplasm. One major class of phosphodiesterases comprises GdpP and DhhP homologs, which degrade c-di-AMP into the linear molecule 5'-pApA or AMP by the DHH-DHHA1 domain. The other major class comprises PgpH homologs, which degrade c-di-AMP by the HD domain. Both GdpP and PgpH harbor sensory domains, likely to regulate c-di-AMP hydrolysis activity in response to signal input. As another possible mechanism for controlling cytoplasmic c-di-AMP levels, bacteria also secrete c-di-AMP via multidrug resis...
Source: Current Opinion in Microbiology - January 7, 2016 Category: Microbiology Authors: Huynh TN, Woodward JJ Tags: Curr Opin Microbiol Source Type: research

The unmasking of 'junk' RNA reveals novel sRNAs: from processed RNA fragments to marooned riboswitches.
Abstract While the notion that RNAs can function as regulators dates back to early molecular studies of gene regulation of the lac operon, it is only over the last decade that the ubiquity and diversity of regulatory RNAs are being realized. Advancements in high throughput sequencing and the adoption of these approaches to rapidly sequence genomes and transcriptomes and to examine gene expression and RNA binding protein specificity have revealed an ever-expanding RNA world. In this review, we focus on recent studies revealing that RNA fragments cleaved from larger coding or noncoding RNAs can have regulatory funct...
Source: Current Opinion in Microbiology - January 6, 2016 Category: Microbiology Authors: De Lay NR, Garsin DA Tags: Curr Opin Microbiol Source Type: research

Bacterial chemotaxis: information processing, thermodynamics, and behavior.
Abstract Escherichia coli has long been used as a model organism due to the extensive experimental characterization of its pathways and molecular components. Take chemotaxis as an example, which allows bacteria to sense and swim in response to chemicals, such as nutrients and toxins. Many of the pathway's remarkable sensing and signaling properties are now concisely summarized in terms of design (or engineering) principles. More recently, new approaches from information theory and stochastic thermodynamics have begun to address how pathways process environmental stimuli and what the limiting factors are. However, ...
Source: Current Opinion in Microbiology - December 27, 2015 Category: Microbiology Authors: Micali G, Endres RG Tags: Curr Opin Microbiol Source Type: research

Type VI secretion and anti-host effectors.
Abstract Secretion systems play a central role in infectious diseases by enabling pathogenic bacteria to deliver virulence factors into target cells. The type VI secretion system (T6SS) mediates bacterial antagonism in various environments including eukaryotic niches, such as the gut. This molecular machine injects lethal toxins directly in target bacterial cells. It provides an advantage to pathogens encountering the commensal flora of the host and indirectly contributes to colonization and persistence. Yet, the T6SS is not employed for the sole purpose of bacterial killing and several T6SS effectors are dedicate...
Source: Current Opinion in Microbiology - December 23, 2015 Category: Microbiology Authors: Hachani A, Wood TE, Filloux A Tags: Curr Opin Microbiol Source Type: research

Unifying view of stem-loop hairpin RNA as origin of current and ancient parasitic and non-parasitic RNAs, including in giant viruses.
Abstract Putatively, stem-loop RNA hairpins explain networks of selfish elements and RNA world remnants. Their genomic density increases with intracellular lifestyle, especially when comparing giant viruses and their virophages. RNA protogenomes presumably templated for mRNAs and self-replicating stem-loops, ancestors of modern genes and parasitic sequences, including tRNAs and rRNAs. Primary and secondary structure analyses suggest common ancestry for t/rRNAs and parasitic RNAs, parsimoniously link diverse RNA metabolites (replication origins, tRNAs, ribozymes, riboswitches, miRNAs and rRNAs) to parasitic RNAs (r...
Source: Current Opinion in Microbiology - December 21, 2015 Category: Microbiology Authors: Seligmann H, Raoult D Tags: Curr Opin Microbiol Source Type: research

Legionella pneumophila, armed to the hilt: justifying the largest arsenal of effectors in the bacterial world.
Abstract Many bacterial pathogens use dedicated translocation systems to deliver arsenals of effector proteins to their hosts. Once inside the host cytosol, these effectors modulate eukaryotic cell biology to acquire nutrients, block microbial degradation, subvert host defenses, and enable pathogen transmission to other hosts. Among all bacterial pathogens studied to date, the gram-negative pathogen, Legionella pneumophila, maintains the largest arsenal of effectors, with over 330 effector proteins translocated by the Dot/Icm type IVB translocation system. In this review, I will discuss some of the recent work on ...
Source: Current Opinion in Microbiology - December 19, 2015 Category: Microbiology Authors: Ensminger AW Tags: Curr Opin Microbiol Source Type: research

Commensal 'trail of bread crumbs' provide pathogens with a map to the intestinal landscape.
Abstract Growth of a microorganism in a host is essential for infection, and bacterial pathogens have evolved to utilize specific metabolites to enhance replication in vivo. Now, emerging data demonstrate that pathogens rely on microbiota-derived metabolites as a form of bacterial-bacterial communication to gain information about location within a host and modify virulence gene expression accordingly. Thus, metabolite-sensing is critical for pathogens to establish infection. Here, we highlight recent examples of how the foodborne pathogen enterohemorrhagic Escherichia coli O157:H7 (EHEC) exploits microbiota-derive...
Source: Current Opinion in Microbiology - December 17, 2015 Category: Microbiology Authors: Luzader DH, Kendall MM Tags: Curr Opin Microbiol Source Type: research

Reprint of "Prospects for the gliding mechanism of Mycoplasma mobile".
Reprint of "Prospects for the gliding mechanism of Mycoplasma mobile". Curr Opin Microbiol. 2015 Dec 17; Authors: Miyata M, Hamaguchi T Abstract Mycoplasma mobile forms gliding machinery at a cell pole and glides continuously in the direction of the cell pole at up to 4.5μm per second on solid surfaces such as animal cells. This motility system is not related to those of any other bacteria or eukaryotes. M. mobile uses ATP energy to repeatedly catch, pull, and release sialylated oligosaccharides on host cells with its approximately 50-nm long legs. The gliding machinery is a large structu...
Source: Current Opinion in Microbiology - December 17, 2015 Category: Microbiology Authors: Miyata M, Hamaguchi T Tags: Curr Opin Microbiol Source Type: research

Infection in an aging population.
Abstract The global population is rapidly aging. Currently, 566 million people are ≥65 years old worldwide, with estimates of nearly 1.5 billion by 2050, particularly in developing countries. Infections constitute a third of mortality in people ≥65 years old. Moreover, lengthening life spans correlate with increased time in hospitals or long-term care facilities and exposure to drug-resistant pathogens. Indeed, the risk of nosocomial infections increases with age, independent of duration spent in healthcare facilities. In this review, we summarize our understanding of how the aging immune system relates to b...
Source: Current Opinion in Microbiology - December 10, 2015 Category: Microbiology Authors: Kline KA, Bowdish DM Tags: Curr Opin Microbiol Source Type: research

Yersinia versus host immunity: how a pathogen evades or triggers a protective response.
Abstract The human pathogenic Yersinia species cause diseases that represent a significant source of morbidity and mortality. Despite this, specific mechanisms underlying Yersinia pathogenesis and protective host responses remain poorly understood. Recent studies have shown that Yersinia disrupt cell death pathways, perturb inflammatory processes and exploit immune cells to promote disease. The ensuing host responses following Yersinia infection include coordination of innate and adaptive immune responses in an attempt to control bacterial replication. Here, we highlight current advances in our understanding of th...
Source: Current Opinion in Microbiology - November 26, 2015 Category: Microbiology Authors: Chung LK, Bliska JB Tags: Curr Opin Microbiol Source Type: research

Regulation of competence-mediated horizontal gene transfer in the natural habitat of Vibrio cholerae.
Abstract The human pathogen Vibrio cholerae is an autochthonous inhabitant of aquatic environments where it often interacts with zooplankton and their chitinous molts. Chitin induces natural competence for transformation in V. cholerae, a key mode of horizontal gene transfer (HGT). Recent comparative genomic analyses were indicative of extensive HGT in this species. However, we can still expand our understanding of the complex regulatory network that drives competence in V. cholerae. Here, we present recent advances, including the elucidation of bipartite competence regulation mediated by QstR, the inclusion of th...
Source: Current Opinion in Microbiology - November 23, 2015 Category: Microbiology Authors: Metzger LC, Blokesch M Tags: Curr Opin Microbiol Source Type: research

Dual role of arginine metabolism in establishing pathogenesis.
This article sheds light upon the roles of arginine metabolism during pathological conditions and its therapeutic potential. PMID: 26610300 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - November 20, 2015 Category: Microbiology Authors: Gogoi M, Datey A, Wilson KT, Chakravortty D Tags: Curr Opin Microbiol Source Type: research

Of guards, decoys, baits and traps: pathogen perception in plants by type III effector sensors.
Abstract Effector-triggered immunity (ETI) is conferred by dominant plant resistance (R) genes, which encode predominantly nucleotide-binding and leucine-rich repeat domain proteins (NLRs), against cognate microbial avirulence (Avr) genes, which include bacterial type III secreted effectors (T3Es). The 'guard model' describes the mechanism of T3E perception by plants, whereby NLRs monitor host proteins ('sensors') for T3E-induced perturbations. This model has provided a molecular framework to understand T3E perception and has rationalized how plants can use a limited number of NLRs (∼160 in Arabidopsis) to con...
Source: Current Opinion in Microbiology - November 18, 2015 Category: Microbiology Authors: Khan M, Subramaniam R, Desveaux D Tags: Curr Opin Microbiol Source Type: research

Motility in the epsilon-proteobacteria.
Abstract The epsilon-proteobacteria are a widespread group of flagellated bacteria frequently associated with either animal digestive tracts or hydrothermal vents, with well-studied examples in the human pathogens of Helicobacter and Campylobacter genera. Flagellated motility is important to both pathogens and hydrothermal vent members, and a number of curious differences between the epsilon-proteobacterial and enteric bacterial motility paradigms make them worthy of further study. The epsilon-proteobacteria have evolved to swim at high speed and through viscous media that immobilize enterics, a phenotype that may...
Source: Current Opinion in Microbiology - November 16, 2015 Category: Microbiology Authors: Beeby M Tags: Curr Opin Microbiol Source Type: research

Editorial overview: Growth and development-prokaryotes.
PMID: 26570990 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - November 10, 2015 Category: Microbiology Authors: Kearns DB Tags: Curr Opin Microbiol Source Type: research

Diverse mechanisms for inflammasome sensing of cytosolic bacteria and bacterial virulence.
Abstract The inflammasomes are emerging cytosolic defenses against bacterial infections. The inflammasomes converge on inflammatory caspases activation that triggers pyroptosis, and interleukin-1β/18 maturation in the case of caspase-1 activation. The inflammasomes not only detect major bacterial molecules but also sense bacterial virulence activity. Among the canonical caspase-1-activating inflammasomes, the NAIP subfamily of NLR proteins serves as the receptors for bacterial flagellin and type III secretion apparatus; Pyrin indirectly senses Rho modification/inactivation by various bacterial agents; NLRP1 i...
Source: Current Opinion in Microbiology - November 9, 2015 Category: Microbiology Authors: Zhao Y, Shao F Tags: Curr Opin Microbiol Source Type: research

Chewing the fat: lipid metabolism and homeostasis during M. tuberculosis infection.
Abstract The interplay between Mycobacterium tuberculosis lipid metabolism, the immune response and lipid homeostasis in the host creates a complex and dynamic pathogen-host interaction. Advances in imaging and metabolic analysis techniques indicate that M. tuberculosis preferentially associates with foamy cells and employs multiple physiological systems to utilize exogenously derived fatty-acids and cholesterol. Moreover, novel insights into specific host pathways that control lipid accumulation during infection, such as the PPARγ and LXR transcriptional regulators, have begun to reveal mechanisms by which ...
Source: Current Opinion in Microbiology - November 3, 2015 Category: Microbiology Authors: Lovewell RR, Sassetti CM, VanderVen BC Tags: Curr Opin Microbiol Source Type: research

The Type IVB secretion system: an enigmatic chimera.
Abstract Type IV secretion systems (T4SSs) are transporters that span the bacterial inner and outer membranes and deliver substrate biomolecules, including proteins and DNAs, into cells. Recent progress in structural analyses of conjugative plasmid-encoded type IVA secretion systems (T4ASSs) has revealed a unique molecular architecture. The essential virulence system, the Dot/Icm Type IVB secretion system (T4BSS) encoded by the intracellular bacterial pathogen Legionella pneumophila is distantly related to T4ASSs. Molecular and structural analyses of the Dot/Icm T4BSS have provided insights into the mechanisms of ...
Source: Current Opinion in Microbiology - October 31, 2015 Category: Microbiology Authors: Kubori T, Nagai H Tags: Curr Opin Microbiol Source Type: research

Spirochetal motility and chemotaxis in the natural enzootic cycle and development of Lyme disease.
Abstract Two-thirds of all bacterial genomes sequenced to-date possess an organelle for locomotion, referred to as flagella, periplasmic flagella or type IV pili. These genomes may also contain a chemotaxis-signaling system which governs flagellar rotation, thus leading a coordinated function for motility. Motility and chemotaxis are often crucial for infection or disease process caused by pathogenic bacteria. Although motility-associated genes are well-characterized in some organisms, the highly orchestrated synthesis, regulation, and assembly of periplasmic flagella in spirochetes are just being delineated. Rece...
Source: Current Opinion in Microbiology - October 27, 2015 Category: Microbiology Authors: Motaleb MA, Liu J, Mark Wooten R Tags: Curr Opin Microbiol Source Type: research

Prospects for the gliding mechanism of Mycoplasma mobile.
Abstract Mycoplasma mobile forms gliding machinery at a cell pole and glides continuously in the direction of the cell pole at up to 4.5μm per second on solid surfaces such as animal cells. This motility system is not related to those of any other bacteria or eukaryotes. M. mobile uses ATP energy to repeatedly catch, pull, and release sialylated oligosaccharides on host cells with its approximately 50-nm long legs. The gliding machinery is a large structure composed of huge surface proteins and internal jellyfish-like structure. This system may have developed from an accidental combination between an adhesin an...
Source: Current Opinion in Microbiology - October 20, 2015 Category: Microbiology Authors: Miyata M, Hamaguchi T Tags: Curr Opin Microbiol Source Type: research

Undiscovered regions on the molecular landscape of flagellar assembly.
Abstract The bacterial flagellum is a motility structure and one of the most complicated motors in the biosphere. A flagellum consists of several dozens of building blocks in different stoichiometries and extends from the cytoplasm to the extracellular space. Flagellar biogenesis follows a strict spatio-temporal regime that is guided by a plethora of flagellar assembly factors and chaperones. The goal of this review is to summarize our current structural and mechanistic knowledge of this intricate process and to identify the undiscovered regions on the molecular landscape of flagellar assembly. PMID: 26490009...
Source: Current Opinion in Microbiology - October 19, 2015 Category: Microbiology Authors: Altegoer F, Bange G Tags: Curr Opin Microbiol Source Type: research

Cross-regulation of Pseudomonas motility systems: the intimate relationship between flagella, pili and virulence.
Abstract Pseudomonas aeruginosa navigates using two distinct forms of motility, swimming and twitching. A polar flagellum and Type 4 pili power these movements, respectively, allowing P. aeruginosa to attach to and colonize surfaces. Single cell imaging and particle tracking algorithms have revealed a wide range of bacterial surface behaviors which are regulated by second messengers cyclic-di-GMP and cAMP; the production of these signals is, in turn, responsive to the engagement of motility organelles with a surface. Innate immune defense systems, long known to recognize structural components of flagella, appear t...
Source: Current Opinion in Microbiology - October 15, 2015 Category: Microbiology Authors: Kazmierczak BI, Schniederberend M, Jain R Tags: Curr Opin Microbiol Source Type: research

Interplay between flagellation and cell cycle control in Caulobacter.
Abstract The assembly of the flagellum, a sophisticated nanomachine powering bacterial locomotion in liquids and across surfaces, is highly regulated. In the synchronizable α-Proteobacterium Caulobacter crescentus, the flagellum is built at a pre-selected cell pole and flagellar transcript abundance oscillates during the cell cycle. Conserved regulators not only dictate when the transcripts encoding flagellar structural proteins peak, but also those encoding polarization factors. Additionally, post-transcriptional cell cycle cues facilitate flagellar (dis-)assembly at the new cell pole. Because of this regul...
Source: Current Opinion in Microbiology - October 15, 2015 Category: Microbiology Authors: Ardissone S, Viollier PH Tags: Curr Opin Microbiol Source Type: research

Towards a model for Flavobacterium gliding.
Abstract Cells of Flavobacterium johnsoniae, a rod-shaped bacterium about 6μm long, do not have flagella or pili, yet they move over surfaces at speeds of about 2μm/s. This motion is called gliding. Recent advances in F. johnsoniae research include the discovery of mobile cell-surface adhesins and rotary motors. The puzzle is how rotary motion leads to linear motion. We suggest a possible mechanism, inspired by the snowmobile. PMID: 26476806 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - October 15, 2015 Category: Microbiology Authors: Shrivastava A, Berg HC Tags: Curr Opin Microbiol Source Type: research

Editorial overview: Microbial systems biology.
PMID: 26483052 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - October 15, 2015 Category: Microbiology Authors: Brown ED, Typas A Tags: Curr Opin Microbiol Source Type: research

Flavobacterium gliding motility and the type IX secretion system.
Abstract Cells of Flavobacterium johnsoniae crawl rapidly over surfaces in a process called gliding motility. These cells do not have flagella or pili but instead rely on a novel motility machine composed of proteins that are unique to the phylum Bacteroidetes. The motility adhesins SprB and RemA are propelled along the cell surface by the still poorly-defined gliding motor. Interaction of these adhesins with a surface results in translocation of the cell. SprB and RemA are delivered to the cell surface by the type IX secretion system (T9SS). T9SSs are confined to but common in the phylum Bacteroidetes. Transmembr...
Source: Current Opinion in Microbiology - October 10, 2015 Category: Microbiology Authors: McBride MJ, Nakane D Tags: Curr Opin Microbiol Source Type: research

Dining in: intracellular bacterial pathogen interplay with autophagy.
Abstract Intracellular bacterial pathogens have evolved many ways to manipulate host cells for successful infection. Many of these pathogens use specialized secretion systems to inject bacterial proteins into the host cytosol that manipulate cellular processes to favor infection. Autophagy is a eukaryotic cellular remodeling process with a critical role in many diseases, including bacterial clearance. A growing field of research highlights mechanisms used by intracellular bacteria to manipulate autophagy as a pro-survival strategy. This review focuses on a select group of bacterial pathogens with diverse intracell...
Source: Current Opinion in Microbiology - October 10, 2015 Category: Microbiology Authors: Winchell CG, Steele S, Kawula T, Voth DE Tags: Curr Opin Microbiol Source Type: research