36 research outputs found
The Intestinal Microbiota Plays a Role in Salmonella-Induced Colitis Independent of Pathogen Colonization
The intestinal microbiota is composed of hundreds of species of bacteria, fungi
and protozoa and is critical for numerous biological processes, such as nutrient
acquisition, vitamin production, and colonization resistance against bacterial
pathogens. We studied the role of the intestinal microbiota on host resistance
to Salmonella enterica serovar Typhimurium-induced colitis.
Using multiple antibiotic treatments in 129S1/SvImJ mice, we showed that
disruption of the intestinal microbiota alters host susceptibility to infection.
Although all antibiotic treatments caused similar increases in pathogen
colonization, the development of enterocolitis was seen only when streptomycin
or vancomycin was used; no significant pathology was observed with the use of
metronidazole. Interestingly, metronidazole-treated and infected C57BL/6 mice
developed severe pathology. We hypothesized that the intestinal microbiota
confers resistance to infectious colitis without affecting the ability of
S. Typhimurium to colonize the intestine. Indeed, different
antibiotic treatments caused distinct shifts in the intestinal microbiota prior
to infection. Through fluorescence in situ hybridization,
terminal restriction fragment length polymorphism, and real-time PCR, we showed
that there is a strong correlation between the intestinal microbiota composition
before infection and susceptibility to Salmonella-induced
colitis. Members of the Bacteroidetes phylum were present at significantly
higher levels in mice resistant to colitis. Further analysis revealed that
Porphyromonadaceae levels were also increased in these mice. Conversely, there
was a positive correlation between the abundance of
Lactobacillus sp. and predisposition to colitis. Our data
suggests that different members of the microbiota might be associated with
S. Typhimurium colonization and colitis. Dissecting the
mechanisms involved in resistance to infection and inflammation will be critical
for the development of therapeutic and preventative measures against enteric
pathogens
Utilisation of Mucin Glycans by the Human Gut Symbiont Ruminococcus gnavus Is Strain-Dependent
Commensal bacteria often have an especially rich source of glycan-degrading enzymes which allow them to utilize undigested carbohydrates from the food or the host. The species Ruminococcus gnavus is present in the digestive tract of ≥90% of humans and has been implicated in gut-related diseases such as inflammatory bowel diseases (IBD). Here we analysed the ability of two R. gnavus human strains, E1 and ATCC 29149, to utilize host glycans. We showed that although both strains could assimilate mucin monosaccharides, only R. gnavus ATCC 29149 was able to grow on mucin as a sole carbon source. Comparative genomic analysis of the two R. gnavus strains highlighted potential clusters and glycoside hydrolases (GHs) responsible for the breakdown and utilization of mucin-derived glycans. Transcriptomic and functional activity assays confirmed the importance of specific GH33 sialidase, and GH29 and GH95 fucosidases in the mucin utilisation pathway. Notably, we uncovered a novel pathway by which R. gnavus ATCC 29149 utilises sialic acid from sialylated substrates. Our results also demonstrated the ability of R. gnavus ATCC 29149 to produce propanol and propionate as the end products of metabolism when grown on mucin and fucosylated glycans. These new findings provide molecular insights into the strain-specificity of R. gnavus adaptation to the gut environment advancing our understanding of the role of gut commensals in health and disease
Intestinal microbiota in human health and disease: the impact of probiotics
The complex communities of microorganisms that colonise the human gastrointestinal tract play an important role in human health. The development of culture-independent molecular techniques has provided new insights in the composition and diversity of the intestinal microbiota. Here, we summarise the present state of the art on the intestinal microbiota with specific attention for the application of high-throughput functional microbiomic approaches to determine the contribution of the intestinal microbiota to human health. Moreover, we review the association between dysbiosis of the microbiota and both intestinal and extra-intestinal diseases. Finally, we discuss the potential of probiotic microorganism to modulate the intestinal microbiota and thereby contribute to health and well-being. The effects of probiotic consumption on the intestinal microbiota are addressed, as well as the development of tailor-made probiotics designed for specific aberrations that are associated with microbial dysbiosis