Abstract
Short-chain fatty acids (SCFAs) are bacterial products that are known to be used as energy sources in eukaryotic hosts, whereas their role in the metabolism of intestinal microbes is rarely explored. In the present study, acetic, propionic, butyric, isobutyric, valeric, and isovaleric acid, respectively, were added to a newly defined medium containing Prevotella bryantii B14 cells. After 8 h and 24 h, optical density, pH and SCFA concentrations were measured. Long-chain fatty acid (LCFA) profiles of the bacterial cells were analyzed via gas chromatography-time of flight-mass spectrometry (GC-ToF MS) and proteins were quantified using a mass spectrometry-based, label-free approach. Cultures supplemented with single SCFAs revealed different growth behavior. Structural features of the respective SCFAs were identified in the LCFA profiles, which suggests incorporation into the bacterial membranes. The proteomes of cultures supplemented with acetic and valeric acid differed by an increased abundance of outer membrane proteins. The proteome of the isovaleric acid supplementation showed an increase of proteins in the amino acid metabolism. Our findings indicate a possible interaction between SCFAs, the lipid membrane composition, the abundance of outer membrane proteins, and a modulation of branched chain amino acid biosynthesis by isovaleric acid.
Highlights
Short-chain fatty acids (SCFAs) are formed by the microbial turnover of plant-derived materials in the rumen and serve as major energy source for animals [1]
High bacterial cell densities were measured for valeric acid (Val), while optical density (OD) measurements at 24 h were lowest for the isovaleric acid (iVal) condition
Cell sedimentation in the supplementation with iVal indicated a challenge for P. bryantii, which was most likely be caused by the overload of isovaleric acid and peptides from fermentation of tryptic digested casein
Summary
Short-chain fatty acids (SCFAs) are formed by the microbial turnover of plant-derived materials in the rumen and serve as major energy source for animals [1]. In addition to the utilization of SCFAs by animals, they are required for the growth of certain microorganisms like Prevotella bryantii B1 4 [2], formerly named Bacteroides ruminicola or Prevotella ruminicola subsp. P. bryantii B1 4 on the other hand, is commonly found in the rumen and requires strictly anoxic conditions as well as carbon dioxide, heme, and vitamin K for growth promotion [7,8]. These conditions are usually met by adding rumen fluid to the respective culture media.
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