Search

Accumulating evidence suggests that interactions between the brain and gut microbiota significantly impact brain function and mental health. In the present study, we aimed to investigate whether young, healthy adults without psychiatric diagnoses exhibit differences in metabolic stool and microbiota profiles based on depression/anxiety scores and heart rate variability (HRV) parameters. Untargeted nuclear magnetic resonance-based metabolomics was used to identify fecal metabolic profiles. Results were subjected to multivariate analysis through principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), and the metabolites were identified through VIP score. Metabolites separating asymptomatic and symptomatic groups were acetate, valine, and glutamate, followed by sugar regions, glutamine, acetone, valerate, and acetoacetate. The main metabolites identified in high vagal tone (HVT) and low vagal tone (LVT) groups were acetate, valerate, and glutamate, followed by propionate and butyrate. In addition to the metabolites identified by the PLS-DA test, significant differences in aspartate, sarcosine, malate, and methionine were observed between the groups. Levels of acetoacetate were higher in both symptomatic and LVT groups. Valerate levels were significantly increased in the symptomatic group, while isovalerate, propionate, glutamate, and acetone levels were significantly increased in the LVT group. Furthermore, distinct abundance between groups was only confirmed for the Firmicutes phylum. Differences between participants with high and low vagal tone suggest that certain metabolites are involved in communication between the vagus nerve and the brain. [ABSTRACT FROM AUTHOR]

Quorum sensing is a cell-cell signaling mechanism based on cell density and that involves the production of hormone-like molecules called autoinducers (AI). One of the most studied AIs has been termed AI-2, and its biosynthesis requires the enzyme encoded by luxS. We have previously described for the first time that Bacteroides species can produce molecules with AI-2 activity. In this study, we focus on the detection of luxS and its activity as the AI-2 synthase in Bacteroides species. The strains Bacteroides fragilis B3b and Bacteroides vulgatus ATCC 8482 were selected based on a positive phenotype for AI-2 production and the presence of a putative luxS in the genome, respectively. In order to identify the luxS gene, cloning and heterologous expression strategies were utilized. We demonstrate that both strains contain functional luxS orthologs that can complement AI-2 production in Escherichia coli. [ABSTRACT FROM AUTHOR]

Quorum sensing is a cell-cell signaling mechanism based on cell density and that involves the production of hormone-like molecules called autoinducers (AI). One of the most studied AIs has been termed AI-2, and its biosynthesis requires the enzyme encoded by luxS. We have previously described for the first time that Bacteroides species can produce molecules with AI-2 activity. In this study, we focus on the detection of luxS and its activity as the AI-2 synthase in Bacteroides species. The strains Bacteroides fragilis B3b and Bacteroides vulgatus ATCC 8482 were selected based on a positive phenotype for AI-2 production and the presence of a putative luxS in the genome, respectively. In order to identify the luxS gene, cloning and heterologous expression strategies were utilized. We demonstrate that both strains contain functional luxS orthologs that can complement AI-2 production in Escherichia coli. [ABSTRACT FROM AUTHOR]

Bacteroides fragilis is a minor component of the intestinal microbiota and the most frequently isolated from intra-abdominal infections and bacteremia. Previously, our group has shown that molecules involved in laminin-1 (LMN-1) recognition were present in outer membrane protein extracts of B. fragilis MC2 strain. One of these proteins was identified and showed 98% similarity to a putative B. fragilis plasminogen-binding protein precursor, deposited in the public database. Thus, the objective of this work was to overexpress and further characterize this novel adhesin. The ability of B. fragilis MC2 strain and purified protein to convert plasminogen into plasmin was tested. Our results showed that B. fragilis strain MC2 strain adhered to both LMN-1 and plasminogen and this adhesion was inhibited by either LMN-1 or plasminogen. Regarding the plasminogen activation activity, both the whole bacterial cell and the purified protein converted plasminogen into plasmin similar to streptokinase used as a positive control. Bacterial receptors that recognize plasminogen bind to it and enhance its activation, transforming a nonproteolytic bacterium into a proteolytic one. We present in vitro evidence for a pathogenic function of the plasminogen receptor in promoting adherence to laminin and also the formation of plasmin by B. fragilis. [ABSTRACT FROM AUTHOR]

The β-barrel outer membrane protease Pla from Yersinia pestis is an important virulence factor in plague and enables initiation of the bubonic plague. Pla is a multifunctional protease whose expression also enhances bacterial adherence to extracellular matrix. It has remained uncertain whether the increase in cellular adhesiveness results from modification of the bacterial surface by Pla, or whether the Pla molecule is an adhesin. Pla was purified as a His6-fusion protein from Escherichia coli and reconstituted with lipopolysaccharide to an enzymatically active form. Purified His6-Pla was coated onto fluorescent micro-particles (FMPs) that expressed plasminogen activity. Pla-coated FMPs also bound to laminin and to reconstituted basement membrane (Matrigel) immobilized on permanox slides, whereas only poor activity was seen with lipopolysaccharide-coated FMPs or bovine serum albumin-coated FMPs. The results show that the Pla molecule has intrinsic adhesive properties and that purified transmembrane proteins coated onto FMPs can be used for functional assays. [ABSTRACT FROM AUTHOR]

The epidemiology of antimicrobial resistance of clinical isolates and human intestinal strains of Bacteroides fragilis has assumed great importance in the last few years since this microorganism, like other members of the B. fragilis group, can be responsible for the spread of resistance determinants. It is possible that the presence of B. fragilis in polluted aquatic environments might contribute to the spread of resistance. The antimicrobial resistance profile of 44 clinical B. fragilis strains isolated from 1981–1988 and 1991–1998 from the University hospital of Rio de Janeiro, and of 17 faecal and 17 polluted aquatic environmental B. fragilis strains isolated between 1991 and 1998 was determined. The susceptibility tests against penicillin, cefoxitin, imipenem, meropenem, clindamycin, chloramphenicol and metronidazole were performed by Etest in Wilkins-Chalgren agar enriched with 5% sheep blood. Motivated by some high MIC values for cefoxitin and meropenem, the cfiA gene, which codes for a metallo-β-lactamase, was investigated among all strains, using PCR amplification. The resistance to penicillin was high in the samples from 1981 to 1988 (92.9%) and also in those from 1991 to 1998 (100%), although the MIC90 decreased from 256 mg/L to 24 mg/L. An increase in the resistance level to clindamycin and cefoxitin was seen from one decade to the other, the MIC90 values changing from 4 mg/L to 12 mg/L and from 8 mg/L to 32 mg/L, respectively. The susceptibility profile for metronidazole, chloramphenicol, imipenem and meropenem remained stable, although two clinical strains showed MICs of 6 mg/L and 8 mg/L against meropenem. Almost all human intestinal strains were resistant to penicillin and all of them were susceptible to imipenem, meropenem, chloramphenicol and metronidazole. The MICs of meropenem against two strains isolated from a polluted aquatic environment were 6 mg/L and 32 mg/L. The cfiA gene was detected in five strains, two of which were isolated from clinical specimens against which the MIC values of cefoxitin were high and three from an aquatic environment, whose susceptibility to both cefoxitin and meropenem ranged from sensitive to resistant. [ABSTRACT FROM PUBLISHER]

Quorum sensing is a cell-cell signaling mechanism based on cell density and that involves the production of hormone-like molecules called autoinducers (AI). One of the most studied AIs has been termed AI-2, and its biosynthesis requires the enzyme encoded by luxS. We have previously described for the first time that Bacteroides species can produce molecules with AI-2 activity. In this study, we focus on the detection of luxS and its activity as the AI-2 synthase in Bacteroides species. The strains Bacteroides fragilis B3b and Bacteroides vulgatus ATCC 8482 were selected based on a positive phenotype for AI-2 production and the presence of a putative luxS in the genome, respectively. In order to identify the luxS gene, cloning and heterologous expression strategies were utilized. We demonstrate that both strains contain functional luxS orthologs that can complement AI-2 production in Escherichia coli., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Yersinia pestis protein Pla is a plasmid-coded outer membrane protein with aspartic-protease activity. Pla exhibits a plasminogen (Plg) activator activity (PAA) that promotes the cleavage of Plg to the active serine-protease form called plasmin. Exactly how Pla activates Plg into plasmin remains unclear. To investigate this event, we performed the interactions between the predicted Plg and Pla protein structures by rigid-body docking with the HEX program and evaluated the complex stability by molecular dynamics (MD) using the GROMACS package programs. The predicted docked complex of Plg-Pla shows the same interaction site predicted by experimental site-direct mutagenesis in other studies. After a total of 8 ns of MD simulation, we observed the relaxation of the beta-barrel structure of Pla and the progressive approximation and stabilization between the cleavage site of Plg into the extracellular loops of Pla, followed by the increase in the number of H bonds. We also report here the aminoacids that participate in the active site and the sub sites of interaction. The total understanding of these interactions can be an important tool for drug design against bacterial proteases.