Cellulose-degrading microorganisms involved in the breakdown of plant cell wall material in the human gut remain rather unexplored despite their role in intestinal fermentation. Microcrystalline cellulose-degrading bacteria were previously identified in faeces of methane-excreting individuals, whereas these microorganisms were undetectable in faecal samples from non-methane excretors. This suggested that the structure and activity of the cellulose-degrading community differ in methane- and non-methane-excreting individuals. The purpose of this study was to characterize in depth this cellulose-degrading community in individuals of both CH(4) statuses using both culture-dependent and molecular methods. A new real-time PCR analysis was developed to enumerate microcrystalline cellulose-degrading ruminococci and used to confirm the predominance of these hydrolytic ruminococci in methane excretors. Culture-dependent methods using cell wall spinach (CWS) residue revealed the presence of CWS-degrading microorganisms in all individuals. Characterization of CWS-degrading isolates further showed that the main cellulose-degrading bacteria belong essentially to Bacteroidetes in non-methane-excreting subjects, while they are predominantly represented by Firmicutes in methane-excreting individuals. This taxonomic diversity was associated with functional diversity: the ability to degrade different types of cellulose and to produce H(2) from fermentation differed depending on the species. The structure of the cellulolytic community was shown to vary depending on the presence of methanogens in the human gut.
A strictly anaerobic, cellulolytic strain, designated 18P13 T , was isolated from a human faecal sample. Cells were Gram-positive non-motile cocci. Strain 18P13 T was able to degrade microcrystalline cellulose but the utilization of soluble sugars was restricted to cellobiose. Acetate and succinate were the major end products of cellulose and cellobiose fermentation. 16S rRNA gene sequence analysis revealed that the isolate belonged to the genus Ruminococcus of the family Ruminococcaceae. The closest phylogenetic relative was the ruminal cellulolytic strain Ruminococcus flavefaciens ATCC 19208 T (,95 % 16S rRNA gene sequence similarity). The DNA G+C content of strain 18P13 T was 53.05±0.7 mol%. On the basis of phylogenetic analysis, and morphological and physiological data, strain 18P13 T can be differentiated from other members of the genus Ruminococcus with validly published names. The name Ruminococcus champanellensis sp. nov. is proposed, with 18P13 T (5DSM 18848 T 5JCM 17042 T ) as the type strain.The human large intestine harbours a large diversity of bacterial communities that play a key role in health and disease through their involvement in nutrition, pathogenesis and immunology (Cummings & Macfarlane, 1991;Salminen et al., 1998). A proper understanding of the diversity and functionality of species in the human gut ecosystem is therefore of considerable importance. Over the past 20 years, the microbiota composition has been investigated using both culture-and molecular-based methods and results have revealed the extensive diversity of this ecosystem (Eckburg et al., 2005;Chassard et al., 2008b;Qin et al., 2010). The microbiota is mainly composed of bacteria belonging to three major phyla: 'Bacteroidetes', 'Firmicutes' and 'Actinobacteria'. The genus Ruminococcus represents an important phylogenetic taxon, belonging to phylum 'Firmicutes', and corresponds to 5-15 % of the total bacterial population in the colon (Chassard et al., 2008b; Ramirez-Farias et al., 2009).Presently, the genus Ruminococcus is not monophyletic and is divided into two phylogenetically separate groups.Group I is located within rRNA cluster IV and includes Ruminococcus flavefaciens, the type species of the genus. In the latest edition of Bergey's Manual of Systematic Bacteriology, members of group I were included in the family Ruminococcaceae and should be considered as Ruminococcus sensu stricto (Rainey, 2009a). Members of group II are located within rRNA cluster XIVa, which is now recognized as the family Lachnospiraceae, a large group of phenotypic and phylogenetic heterogeneous genera (Rainey, 2009b). Recently, a number of misclassified Ruminococcus species and a Clostridium species in group II were reclassified in the genus Blautia (Liu et al., 2008). The remaining ruminococci within group II most likely constitute the nuclei of novel genera and should not be considered true ruminococci.The genus Ruminococcus comprises anaerobic Grampositive cocci with a fermentative metabolism for which carbohydrates, but not amino acids, serve...
An integrated analysis of gut microbiota, blood biochemical and metabolome in 52 endurance horses was performed. Clustering by gut microbiota revealed the existence of two communities mainly driven by diet as host properties showed little effect. Community 1 presented lower richness and diversity, but higher dominance and rarity of species, including some pathobionts. Moreover, its microbiota composition was tightly linked to host blood metabolites related to lipid metabolism and glycolysis at basal time. Despite the lower fiber intake, community type 1 appeared more specialized to produce acetate as a mean of maintaining the energy supply as glucose concentrations fell during the race. On the other hand, community type 2 showed an enrichment of fibrolytic and cellulolytic bacteria as well as anaerobic fungi, coupled to a higher production of propionate and butyrate. The higher butyrate proportion in community 2 was not associated with protective effects on telomere lengths but could have ameliorated mucosal inflammation and oxidative status. The gut microbiota was neither associated with the blood biochemical markers nor metabolome during the endurance race, and did not provide a biomarker for race ranking or risk of failure to finish the race.
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