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Objective: The assessment of potentially confounding factors affecting colon microbiota composition is essential to the identification of robust microbiome based disease markers. Here, we investigate the link between gut microbiota variation and stool consistency using Bristol Stool Scale classification, which reflects faecal water content and activity, and is considered a proxy for intestinal colon transit time. Design: Through 16S rDNA Illumina profiling of faecal samples of 53 healthy women, we evaluated associations between microbiome richness, Bacteroidetes:Firmicutes ratio, enterotypes, and genus abundance with self-reported, Bristol Stool Scale-based stool consistency. Each sample's microbiota growth potential was calculated to test whether transit time acts as a selective force on gut bacterial growth rates. Results: Stool consistency strongly correlates with all known major microbiome markers. It is negatively correlated with species richness, positively associated to the Bacteroidetes:Firmicutes ratio, and linked to Akkermansia and Methanobrevibacter abundance. Enterotypes are distinctly distributed over the BSS-scores. Based on the correlations between microbiota growth potential and stool consistency scores within both enterotypes, we hypothesise that accelerated transit contributes to colon ecosystem differentiation. While shorter transit times can be linked to increased abundance of fast growing species in Ruminococcaceae- Bacteroides samples, hinting to a washout avoidance strategy of faster replication, this trend is absent in Prevotella-enterotyped individuals. Within this enterotype adherence to host tissue therefore appears to be a more likely bacterial strategy to cope with washout. Conclusions: The strength of the associations between stool consistency and species richness, enterotypes and community composition emphasises the crucial importance of stool consistency assessment in gut metagenome-wide association studies. [ABSTRACT FROM AUTHOR]

Kinetic analyses of bacterial growth, carbohydrate consumption, and metabolite production of five butyrate- producing clostridial cluster XIVa colon bacteria grown on acetate plus fructose, oligofructose, inulin, or lactate were performed. A gas chromatography method was set up to assess H2 and CO2 production online and to ensure complete coverage of all metabolites produced. Method accuracy was confirmed through the calculation of electron and carbon recoveries. Fermentations with Anaerostipes caccae DSM 14662T, Roseburia faecis DSM 16840T, Roseburia hominis DSM 16839T, and Roseburia intestinalis DSM 14610T revealed similar patterns of metabolite production with butyrate, CO2, and H2 as the main metabolites. R. faecis DSM 16840T and R. intestinalis DSM 14610T were able to degrade oligofructose, displaying a nonpreferential breakdown mechanism. Lactate consumption was only observed with A. caccae DSM 14662T. Roseburia inulinivorans DSM 16841T was the only strain included in the present study that was able to grow on fructose, oligofructose, and inulin. The metabolites produced were lactate, butyrate, and CO2, without H2 production, indicating an energy metabolism distinct from that of other Roseburia species. Oligofructose degradation was nonpreferential. In a coculture of R. inulinivorans DSM 16841T with the highly competitive strain Bifidobacterium longum subsp. longum LMG 11047 on inulin, hardly any production of butyrate and CO2 was detected, indicating a lack of competitiveness of the butyrate producer. Complete recovery of metabolites during fermentations of clostridial cluster XIVa butyrate-producing colon bacteria allowed stoichiometric balancing of the metabolic pathway for butyrate production, including H2 formation. [ABSTRACT FROM AUTHOR]

Kinetic analyses of bacterial growth, carbohydrate consumption, and metabolite production of 18 Bifidobacterium strains grown on fructose, oligofructose, or inulin were performed. A principal component analysis of the data sets, expanded with the results of a genetic screen concerning the presence of a β-fructofuranosidase gene previously encountered in Bifidobacterium animalis subsp. lactis DSM 10140T, revealed the existence of four clusters among the bifidobacteria tested. Strains belonging to a first cluster could not degrade oligofructose or inulin. Strains in a second cluster could degrade oligofructose, displaying a preferential breakdown mechanism, but did not grow on inulin. Fructose consumption was faster than oligofructose degradation. A third cluster was composed of strains that degraded all oligofructose fractions simultaneously and could partially break down inulin. Oligofructose degradation was substantially faster than fructose consumption. A fourth, smaller cluster consisted of strains that shared high fructose consumption and oligofructose degradation rates and were able to perform partial breakdown of inulin. For all strains, a metabolic shift toward more acetate, formate, and ethanol production, at the expense of lactate production, was observed during growth on less readily fermentable energy sources. No correlation between breakdown patterns and the presence of the f3-fructofuranosidase gene could be detected. These variations indicate niche-specific adaptation of bifidobacteria and could have in vivo implications on the strain specificity of the stimulatory effect of inulin-type fructans on bifidobacteria. [ABSTRACT FROM AUTHOR]

In vitro coculture fermentations of Bifidobacterium longum BB536 and two acetate-converting, butyrate-producing colon bacteria, Anaerostipes caccae DSM 14662 and Roseburia intestinalis DSM 14610, with oligo-fructose as the sole energy source, were performed to study interspecies interactions. Two clearly distinct types of cross-feeding were identified. A. caccae DSM 14662 was not able to degrade oligofructose but could grow on the fructose released by B. longum BB536 during oligofructose breakdown. R. intestinalis DSM 14610 could degrade oligofructose, but only after acetate was added to the medium. Detailed kinetic analyses of oligofructose breakdown by the last strain revealed simultaneous degradation of the different chain length fractions, in contrast with the preferential degradation of shorter fractions by B. longum BB536. In a coculture of both strains, initial oligofructose degradation and acetate production by B. longum BB536 took place, which in turn also allowed oligofructose breakdown by R. intestinalis DSM 14610. These and similar cross-feeding mechanisms could play a role in the colon ecosystem and contribute to the combined bifidogenic/butyrogenic effect observed after addition of inulin-type fructans to the diet. [ABSTRACT FROM AUTHOR]

Abstract: Metabolite production due to bacterial outgrowth and oxidation phenomena lead to spoilage development of cooked ham. Artisan-type products, with low salt concentrations and a minimum of additives, are particularly sensitive. Cold chain variations related to distribution and consumer habits have a negative influence on the shelf-life. In this study, sliced, modified atmosphere packaged artisan-type cooked ham was stored at different temperatures (4, 7, 12, and 26°C). The evolution of volatiles over time for the different storage temperatures was monitored with static headspace gas chromatography/mass spectrometry (SH–GC–MS). The latter method was compared to solid phase microextraction (SPME). Several of the detected compounds could be ascribed to bacterial glucose and amino acid metabolism and their production was related to the storage temperature. The compounds 3-methyl butanol and ethanol were related with bacterial cell growth. Maillard-derived compounds, leading to the formation of furans, probably originated from endogenous reactions during cooking. Several detected aliphatic compounds probably originated from fatty acid oxidation reactions, including thermal fat degradation, chemical auto-oxidation, and enzymatic β-oxidation. [Copyright &y& Elsevier]