Catálogo de publicaciones - revistas

<jats:p> The longstanding interactions between mammals and their symbionts enable thousands of mammal species to consume herbivorous diets. The microbial communities in mammals degrade both plant fiber and toxins. Microbial toxin degradation has been repeatedly documented in domestic ruminants, but similar work in wild mammals is more limited due to constraints on sampling and manipulating the microbial communities in these species. In this review, we briefly describe the toxins commonly encountered in mammalian diets, major classes of biotransformation enzymes in microbes and mammals, and the gut chambers that house symbiotic microbes. We next examine evidence for microbial detoxification in domestic ruminants before providing case studies on microbial toxin degradation in both foregut- and hindgut-fermenting wild mammals. We end by discussing species that may be promising for future investigations, and the advantages and limitations of approaches currently available for studying degradation of toxins by mammalian gut microbes. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> Heterocyst differentiation that occurs in some filamentous cyanobacteria, such as Anabaena sp. PCC 7120, provides a unique model for prokaryotic developmental biology. Heterocyst cells are formed in response to combined-nitrogen deprivation and possess a microoxic environment suitable for nitrogen fixation following extensive morphological and physiological reorganization. A filament of Anabaena is a true multicellular organism, as nitrogen and carbon sources are exchanged among different cells and cell types through septal junctions to ensure filament growth. Because heterocysts are terminally differentiated cells and unable to divide, their activity is an altruistic behavior dedicated to providing fixed nitrogen for neighboring vegetative cells. Heterocyst development is also a process of one-dimensional pattern formation, as heterocysts are semiregularly intercalated among vegetative cells. Morphogens form gradients along the filament and interact with each other in a fashion that fits well into the Turing model, a mathematical framework to explain biological pattern formation. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> RNA degradosomes are multienzyme complexes composed of ribonucleases, RNA helicases, and metabolic enzymes. RNase E–based degradosomes are widespread in Proteobacteria. The Escherichia coli RNA degradosome is sequestered from transcription in the nucleoid and translation in the cytoplasm by localization to the inner cytoplasmic membrane, where it forms short-lived clusters that are proposed to be sites of mRNA degradation. In Caulobacter crescentus, RNA degradosomes localize to ribonucleoprotein condensates in the interior of the cell [bacterial ribonucleoprotein-bodies (BR-bodies)], which have been proposed to drive the concerted degradation of mRNA to nucleotides. The turnover of mRNA in growing cells is important for maintaining pools of nucleotides for transcription and DNA replication. Membrane attachment of the E. coli RNA degradosome is necessary to avoid wasteful degradation of intermediates in ribosome assembly. Sequestering RNA degradosomes to C. crescentus BR-bodies, which exclude structured RNA, could have a similar role in protecting intermediates in ribosome assembly from degradation. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> Archaea remains the least-studied and least-characterized domain of life despite its significance not just to the ecology of our planet but also to the evolution of eukaryotes. It is therefore unsurprising that research into horizontal gene transfer (HGT) in archaea has lagged behind that of bacteria. Indeed, several archaeal lineages may owe their very existence to large-scale HGT events, and thus understanding both the molecular mechanisms and the evolutionary impact of HGT in archaea is highly important. Furthermore, some mechanisms of gene exchange, such as plasmids that transmit themselves via membrane vesicles and the formation of cytoplasmic bridges that allows transfer of both chromosomal and plasmid DNA, may be archaea specific. This review summarizes what we know about HGT in archaea, and the barriers that restrict it, highlighting exciting recent discoveries and pointing out opportunities for future research. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> During the essential processes of DNA replication and transcription, RNA-DNA hybrid intermediates are formed that pose significant risks to genome integrity when left unresolved. To manage RNA-DNA hybrids, all cells rely on RNase H family enzymes that specifically cleave the RNA portion of the many different types of hybrids that form in vivo. Recent experimental advances have provided new insight into how RNA-DNA hybrids form and the consequences to genome integrity that ensue when persistent hybrids remain unresolved. Here we review the types of RNA-DNA hybrids, including R-loops, RNA primers, and ribonucleotide misincorporations, that form during DNA replication and transcription and discuss how each type of hybrid can contribute to genome instability in bacteria. Further, we discuss how bacterial RNase HI, HII, and HIII and bacterial FEN enzymes contribute to genome maintenance through the resolution of hybrids. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> Microbial communities enmeshed in a matrix of macromolecules, termed as biofilms, are the natural setting of bacteria. Exopolysaccharide is a critical matrix component of biofilms. Here, we focus on biofilm matrix exopolysaccharides in Pseudomonas aeruginosa. This opportunistic pathogen can adapt to a wide range of environments and can form biofilms or aggregates in a variety of surfaces or environments, such as the lungs of people with cystic fibrosis, catheters, wounds, and contact lenses. The ability to synthesize multiple exopolysaccharides is one of the advantages that facilitate bacterial survival in different environments. P. aeruginosa can produce several exopolysaccharides, including alginate, Psl, Pel, and lipopolysaccharide. In this review, we highlight the roles of each exopolysaccharide in P. aeruginosa biofilm development and how bacteria coordinate the biosynthesis of multiple exopolysaccharides and bacterial motility. In addition, we present advances in antibiofilm strategies targeting matrix exopolysaccharides, with a focus on glycoside hydrolases. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> Extensive research has elucidated the influence of the gut microbiota on human health and disease susceptibility and resistance. We review recent clinical and laboratory-based experimental studies associating the gut microbiota with certain human diseases. We also highlight ongoing translational advances that manipulate the gut microbiota to treat human diseases and discuss opportunities and challenges in translating microbiome research from and to the bedside. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> Diversity-generating retroelements (DGRs) create vast amounts of targeted, functional diversity by facilitating the rapid evolution of ligand-binding protein domains. Thousands of DGRs have been identified in bacteria, archaea, and their respective viruses. They are broadly distributed throughout the microbial world, with enrichment observed in certain taxa and environments. The diversification machinery works through a novel mechanism termed mutagenic retrohoming, whereby nucleotide sequence information is copied from an invariant DNA template repeat (TR) into an RNA intermediate, selectively mutagenized at TR adenines during cDNA synthesis by a DGR-encoded reverse transcriptase, and transferred to a variable repeat (VR) region within a variable-protein gene (54). This unidirectional flow of information leaves TR-DNA sequences unmodified, allowing for repeated rounds of mutagenic retrohoming to optimize variable-protein function. DGR target genes are often modular and can encode one or more of a wide variety of discrete functional domains appended to a diversifiable ligand-binding motif. Bacterial variable proteins often localize to cell surfaces, although a subset appear to be cytoplasmic, while phage-encoded DGRs commonly diversify tail fiber–associated receptor-binding proteins. Here, we provide a comprehensive review of the mechanism and consequences of accelerated protein evolution by these unique and beneficial genetic elements. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> The Omp85 protein superfamily is found in the outer membrane (OM) of all gram-negative bacteria and eukaryotic organelles of bacterial origin. Members of the family catalyze both the membrane insertion of β-barrel proteins and the translocation of proteins across the OM. Although the mechanism(s) by which these proteins function is unclear, striking new insights have emerged from recent biochemical and structural studies. In this review we discuss the entire Omp85 superfamily but focus on the function of the best-studied member, BamA, which is an essential and highly conserved component of the bacterial barrel assembly machinery (BAM). Because BamA has multiple functions that overlap with those of other Omp85 proteins, it is likely the prototypical member of the Omp85 superfamily. Furthermore, BamA has become a protein of great interest because of the recent discovery of small-molecule inhibitors that potentially represent an important new class of antibiotics. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>

<jats:p> Antibiotic resistance is a serious public health concern, and new drugs are needed to ensure effective treatment of many bacterial infections. Bacterial type II fatty acid synthesis (FASII) is a vital aspect of bacterial physiology, not only for the formation of membranes but also to produce intermediates used in vitamin production. Nature has evolved a repertoire of antibiotics inhibiting different aspects of FASII, validating these enzymes as potential targets for new antibiotic discovery and development. However, significant obstacles have been encountered in the development of FASII antibiotics, and few FASII drugs have advanced beyond the discovery stage. Most bacteria are capable of assimilating exogenous fatty acids. In some cases they can dispense with FASII if fatty acids are present in the environment, making the prospects for identifying broad-spectrum drugs against FASII targets unlikely. Single-target, pathogen-specific FASII drugs appear the best option, but a major drawback to this approach is the rapid acquisition of resistance via target missense mutations. This complication can be mitigated during drug development by optimizing the compound design to reduce the potential impact of on-target missense mutations at an early stage in antibiotic discovery. The lessons learned from the difficulties in FASII drug discovery that have come to light over the last decade suggest that a refocused approach to designing FASII inhibitors has the potential to add to our arsenal of weapons to combat resistance to existing antibiotics. </jats:p><jats:p> Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. </jats:p>