Abstract
Many functions in host–microbiota interactions are potentially influenced by intestinal transit times, but little is known about the effects of altered transition times on the composition and functionality of gut microbiota. To analyze these effects, we cultivated the model community SIHUMIx in bioreactors in order to determine the effects of varying transit times (TT) on the community structure and function. After five days of continuous cultivation, we investigated the influence of different medium TT of 12 h, 24 h, and 48 h. For profiling the microbial community, we applied flow cytometric fingerprinting and revealed changes in the community structure of SIHUMIx during the change of TT, which were not associated with changes in species abundances. For pinpointing metabolic alterations, we applied metaproteomics and metabolomics and found, along with shortening the TT, a slight decrease in glycan biosynthesis, carbohydrate, and amino acid metabolism and, furthermore, a reduction in butyrate, methyl butyrate, isobutyrate, valerate, and isovalerate concentrations. Specifically, B. thetaiotaomicron was identified to be affected in terms of butyrate metabolism. However, communities could recover to the original state afterward. This study shows that SIHUMIx showed high structural stability when TT changed—even four-fold. Resistance values remained high, which suggests that TTs did not interfere with the structure of the community to a certain degree.
Highlights
The human intestine harbors hundreds of bacterial species that are associated with human health and disease [1,2]
This study shows that SIHUMIx showed high structural stability when transit times (TT) changed—even four-fold
We found that SIHUMIx maintained its structure to a high degree when cultivated continuously and reached the ability to stay essentially unchanged after five days, which serves as the starting point for experimental treatments (Krause et al, in revision at Gut Microbes journal)
Summary
The human intestine harbors hundreds of bacterial species that are associated with human health and disease [1,2] This association is mainly due to changes in metabolic interactions with the host caused by changes in the bacterial community structure and function. BCFA such as isovalerate, isobutyrate, and 2-methyl butyrate are produced due to the fermentation of valine, leucine, and isoleucine and serve as precursors for fatty acid synthesis or as nitrogen donors for the production of other amino acids [7,8]. The concentration of these bioactive compounds depends on daily food intake and the type of food. Changes in nutrient concentrations can vary due to different amounts of food intake and due to variations in intestinal transit times, dietary amount, and health state (e.g., infections) [9]
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