A ubiquitous mobile genetic element changes the antagonistic weaponry of a human gut symbiont.

DNA transfer is ubiquitous in the human gut microbiota, especially among species of the order Bacteroidales. In silico analyses have revealed hundreds of mobile genetic elements shared between these species, yet little is known about the phenotypes they encode, their effects on fitness, or pleiotropic consequences for the recipient's genome. In this work, we show that acquisition of a ubiquitous integrative conjugative element (ICE) encoding a type VI secretion system (T6SS) shuts down the native T6SS of .

A ubiquitous mobile genetic element disarms a bacterial antagonist of the gut microbiota.

DNA transfer is ubiquitous in the gut microbiota, especially among species of Bacteroidales. analyses have revealed hundreds of mobile genetic elements shared between these species, yet little is known about the phenotypes they encode, their effects on fitness, or pleiotropic consequences for the recipient's genome. Here, we show that acquisition of a ubiquitous integrative and conjugative element encoding an antagonistic system shuts down the native contact-dependent antagonistic system of .

A family of anti-Bacteroidales peptide toxins wide-spread in the human gut microbiota.

Bacteria often produce antimicrobial toxins to compete in microbial communities. Here we identify a family of broad-spectrum peptide toxins, named bacteroidetocins, produced by Bacteroidetes species. We study this toxin family using phenotypic, mutational, bioinformatic, and human metagenomic analyses.

Acquisition of MACPF domain-encoding genes is the main contributor to LPS glycan diversity in gut Bacteroides species.

The ability to antagonize competing strains and species is often important for bacterial fitness in microbial communities. The extent to which intra-species antagonism drives phenotypic diversity of bacterial species is rarely examined in a comprehensive manner at both the genetic and phenotypic levels. Here we show that for nine abundant human gut Bacteroides species examined, there are only a few LPS glycan genetic types.

Gut Symbiont Secretes a Eukaryotic-Like Ubiquitin Protein That Mediates Intraspecies Antagonism.

Human gut species produce different types of toxins that antagonize closely related members of the gut microbiota. Some are toxic effectors delivered by type VI secretion systems, and others are non-contact-dependent secreted antimicrobial proteins. Many strains of secrete antimicrobial molecules, but only one of these toxins has been described to date ( secreted antimicrobial protein 1 [BSAP-1]).

Bacteroidales Secreted Antimicrobial Proteins Target Surface Molecules Necessary for Gut Colonization and Mediate Competition In Vivo.

Unlabelled: We recently showed that human gut Bacteroidales species secrete antimicrobial proteins (BSAPs), and we characterized in vitro the first such BSAP produced by Bacteroides fragilis In this study, we identified a second potent BSAP produced by the ubiquitous and abundant human gut species Bacteroides uniformis The two BSAPs contain a membrane attack complex/perforin (MACPF) domain but share very little sequence similarity. We identified the target molecules of BSAP-sensitive cells and showed that each BSAP targets a different class of surface molecule: BSAP-1 targets an outer membrane protein of sensitive B. fragilis strains, and BSAP-2 targets the O-antigen glycan of lipopolysaccharide (LPS) of sensitive B.

Bacteroides fragilis type VI secretion systems use novel effector and immunity proteins to antagonize human gut Bacteroidales species.

Type VI secretion systems (T6SSs) are multiprotein complexes best studied in Gram-negative pathogens where they have been shown to inhibit or kill prokaryotic or eukaryotic cells and are often important for virulence. We recently showed that T6SS loci are also widespread in symbiotic human gut bacteria of the order Bacteroidales, and that these T6SS loci segregate into three distinct genetic architectures (GA). GA1 and GA2 loci are present on conserved integrative conjugative elements (ICE) and are transferred and shared among diverse human gut Bacteroidales species.

Friend turned foe: a role for bacterial sulfatases in colitis.

During colitis, gut bacteria and bacterial components can traverse the mucus layer and contact host cells. In this issue of Cell Host & Microbe, Hickey et al. (2015) show that sulfatases of Bacteroides thetaiotaomicron are required for its outer membrane vesicles to transit to underlying host immune cells and cause colitis.

An antimicrobial protein of the gut symbiont Bacteroides fragilis with a MACPF domain of host immune proteins.

Bacteroidales are the most abundant Gram-negative bacteria of the human intestinal microbiota comprising more than half of the bacteria in many individuals. Some of the factors that these bacteria use to establish and maintain themselves in this ecosystem are beginning to be identified. However, ecological competition, especially interference competition where one organism directly harms another, is largely unexplored.

Phylum-wide general protein O-glycosylation system of the Bacteroidetes.

The human gut symbiont Bacteroides fragilis has a general protein O-glycosylation system in which numerous extracytoplasmic proteins are glycosylated at a three amino acid motif. In B. fragilis, protein glycosylation is a fundamental and essential property as mutants with protein glycosylation defects have impaired growth and are unable to competitively colonize the mammalian intestine.

Trans locus inhibitors limit concomitant polysaccharide synthesis in the human gut symbiont Bacteroides fragilis.

Bacteroides is an abundant genus of bacteria of the human intestinal microbiota. Bacteroides species synthesize a large number of capsular polysaccharides (PS), a biological property not shared with closely related oral species, suggesting importance for intestinal survival. Bacteroides fragilis, for example, synthesizes eight capsular polysaccharides per strain, each of which phase varies via inversion of the promoters located upstream of seven of the eight polysaccharide biosynthesis operons.

A family of transcriptional antitermination factors necessary for synthesis of the capsular polysaccharides of Bacteroides fragilis.

A single strain of Bacteroides fragilis synthesizes eight distinct capsular polysaccharides, designated PSA to PSH. These polysaccharides are synthesized by-products encoded by eight separate polysaccharide biosynthesis loci. The genetic architecture of each of these eight loci is similar, including the fact that the first gene of each locus is a paralog of the first gene of each of the other PS loci.

A general O-glycosylation system important to the physiology of a major human intestinal symbiont.

The Bacteroides are a numerically dominant genus of the human intestinal microbiota. These organisms harbor a rare bacterial pathway for incorporation of exogenous fucose into capsular polysaccharides and glycoproteins. The infrequency of glycoprotein synthesis by bacteria prompted a more detailed analysis of this process.

Role of glycan synthesis in colonization of the mammalian gut by the bacterial symbiont Bacteroides fragilis.

Bacteroides species are the most abundant Gram-negative bacteria of the human colonic microbiota. These endogenous organisms are unique in that they synthesize an extensive number of phase-variable surface polysaccharides. Pathogenic bacteria phase vary expression of surface molecules for immune evasion, but the importance of the synthesis of multiple phase-variable polysaccharides to these commensal bacteria is unknown.

Expression of a uniquely regulated extracellular polysaccharide confers a large-capsule phenotype to Bacteroides fragilis.

Bacteroides fragilis synthesizes eight distinct capsular polysaccharides, more than any described bacterium outside the order Bacteroidales. Here, we show that this organism also produces a high-molecular-weight extracellular polysaccharide (EPS). Expression of the EPS results in the formation of a large polysaccharide layer around the bacteria which prevents them from forming a tight pellet upon centrifugation and from entering a Percoll density gradient.

Bacteroides fragilis synthesizes a DNA invertase affecting both a local and a distant region.

The activity of a fourth conserved tyrosine site-specific recombinase (Tsr) of Bacteroides fragilis was characterized. Its gene, tsr19, is adjacent to mpi, encoding the global DNA invertase regulating capsular polysaccharide biosynthesis. Unlike the other described Tsrs of B.

Genetic distinctions among clinical and environmental strains of Vibrio vulnificus.

Vibrio vulnificus causes rare but frequently fatal septicemia associated with raw oyster consumption by persons with underlying hepatic or immune system dysfunction. The virulence potential of environmental reservoirs appears widely distributed, because most strains are virulent in animal models; however, several investigations recently demonstrated genetic divergence among strains from clinical versus environmental origin at independent genetic loci. The present study used PCR to screen DNA polymorphisms in strains from environmental (n = 35) or clinical (n = 33) sources, and genomic relationships were determined by repetitive extragenic palindromic DNA PCR (rep-PCR) typing.

Genetic variation in the Vibrio vulnificus group 1 capsular polysaccharide operon.

Vibrio vulnificus produces human disease associated with raw-oyster consumption or wound infections, but fatalities are limited to persons with chronic underlying illness. Capsular polysaccharide (CPS) is required for virulence, and CPS expression correlates with opaque (Op) colonies that show "phase variation" to avirulent translucent (Tr) phenotypes with reduced CPS. The results discussed here confirmed homology of a V.