RESUMO
The immune system responds vigorously to microbial infection while permitting lifelong colonization by the microbiome. Mechanisms that facilitate the establishment and stability of the gut microbiota remain poorly described. We found that a regulatory system in the prominent human commensal Bacteroides fragilis modulates its surface architecture to invite binding of immunoglobulin A (IgA) in mice. Specific immune recognition facilitated bacterial adherence to cultured intestinal epithelial cells and intimate association with the gut mucosal surface in vivo. The IgA response was required for B. fragilis (and other commensal species) to occupy a defined mucosal niche that mediates stable colonization of the gut through exclusion of exogenous competitors. Therefore, in addition to its role in pathogen clearance, we propose that IgA responses can be co-opted by the microbiome to engender robust host-microbial symbiosis.
Assuntos
Bacteroides fragilis/imunologia , Microbioma Gastrointestinal/imunologia , Imunoglobulina A/imunologia , Mucosa Intestinal/imunologia , Mucosa Intestinal/microbiologia , Animais , Aderência Bacteriana/imunologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Bacteroides fragilis/genética , Bacteroides fragilis/ultraestrutura , Células Cultivadas , Humanos , Camundongos , Polissacarídeos Bacterianos/imunologia , SimbioseRESUMO
Our understanding of the molecular mechanisms involved in biofilm formation has increased tremendously in recent years. From research on diverse bacteria, a general model of bacterial biofilm development has emerged. This model can be adjusted to fit either of two common modes of unicellular existence: nonmotile and motile. Here we provide a detailed review of what is currently known about biofilm formation by the motile bacterium Bacillus subtilis. While the ability of bacteria to form a biofilm appears to be almost universal and overarching themes apply, the combination of molecular events necessary varies widely, and this is reflected in the other chapters of this book.
Assuntos
Bacillus subtilis/fisiologia , Biofilmes/crescimento & desenvolvimento , Bacillus subtilis/genética , Aderência Bacteriana/fisiologiaRESUMO
When exponential-phase cultures of Deinococcus radiodurans are exposed to a 5000-Gray dose of gamma radiation, individual cells suffer massive DNA damage. Despite this insult to their genetic integrity, these cells survive without loss of viability or evidence of mutation, repairing the damage by as-yet-poorly-understood mechanisms.
