Valerate production by Megasphaera elsdenii isolated from pig feces.

Megasphaera elsdenii is able to produce several short-chain fatty acids (SCFAs), such as acetate, propionate, butyrate, and valerate. These SCFAs serve as an energy source for host animals and play an important role in gut health. In this study, M. elsdenii was isolated from pig feces that had been collected from two farms located in distinct areas of Japan. These M. elsdenii isolates were genotyped, and 7 representative strains were selected. When these 7 strains and M. elsdenii JCM 1772T were cultured with lactate for 24 h, all 7 strains produced valerate as a predominant SCFA. Therefore, the valerate-producing M. elsdenii inhabits a wide area of Japan. In contrast, M. elsdenii JCM 1772T produced acetate, propionate, butyrate, and valerate at similar levels. When the Y2 strain, one of the 7 representative strains, was cultured without lactate, low levels of valerate accumulated. In contrast, in a time course of lactate fermentation by the Y2 strain, lactate was rapidly consumed, and acetate and propionate were produced after 6 h of incubation. Thereafter, acetate and propionate were consumed from 6 to 12 h after the start of the incubation, and valerate and butyrate were produced. In most of the previously described M. elsdenii strains, valerate was not a predominant SCFA. Therefore, the M. elsdenii Y2 strain showed an unique metabolism in which valerate was produced as a primary end product of lactate fermentation.

Preferential isolation of Megasphaera elsdenii from pig feces.

Lactic acid produced by intestinal bacteria is fermented by lactate-utilizing bacteria. In this study, we developed a selective culture medium (KMI medium) for Megasphaera elsdenii, a lactate-utilizing bacterium that is abundant in pig intestines. Supplementation of the medium with lactate and beef extract powder was necessary for the preferential growth of M. elsdenii. In addition, we designed a species-specific primer set to detect M. elsdenii. When pig fecal samples were plated on KMI agar medium, approximately 60-100% of the resulting colonies tested positive using the M. elsdenii-specific PCR primers. In fact, nearly all of the large, yellow-white colonies that grew on the KMI agar medium tested positive by PCR with this primer set. The 16S rRNA gene sequences of three representative PCR-positive strains showed strong similarities to that of M. elsdenii ATCC 25940T (98.9-99.2% identity). These three strains were approximately 1.5 µm sized cocci that were primarily arranged in pairs, as was observed for M. elsdenii JCM 1772T. The selective KMI medium and species-specific primer set developed in this study are useful for the isolation and detection of M. elsdenii and will be useful in research aimed at increasing our understanding of intestinal short-chain fatty acid metabolism in pigs.

Rumen microbial abundance and fermentation profile during severe subacute ruminal acidosis and its modulation by plant derived alkaloids in vitro.

Rumen microbiota have important metabolic functions for the host animal. This study aimed at characterizing changes in rumen microbial abundances and fermentation profiles using a severe subacute ruminal acidosis (SARA) in vitro model, and to evaluate a potential modulatory role of plant derived alkaloids (PDA), containing quaternary benzophenanthridine and protopine alkaloids, of which sanguinarine and chelerythrine were the major bioactive compounds. Induction of severe SARA strongly affected the rumen microbial composition and fermentation variables without suppressing the abundance of total bacteria. Protozoa and fungi were more sensitive to the low ruminal pH condition than bacteria. Induction of severe SARA clearly depressed degradation of fiber (P < 0.001), which came along with a decreased relative abundance of fibrolytic Ruminococcus albus and Fibrobacter succinogenes (P < 0.001). Under severe SARA conditions, the genus Prevotella, Lactobacillus group, Megasphaera elsdenii, and Entodinium spp. (P < 0.001) were more abundant, whereas Ruminobacter amylophilus was less abundant. SARA largely suppressed methane formation (-70%, P < 0.001), although total methanogenic 16S rRNA gene abundance was not affected. According to principal component analysis, Methanobrevibacter spp. correlated to methane concentration. Addition of PDA modulated ruminal fermentation under normal conditions such as enhanced (P < 0.05) concentration of total SCFA, propionate and valerate, and increased (P < 0.05) degradation of crude protein compared with the unsupplemented control diet. Our results indicate strong shifts in the microbial community during severe SARA compared to normal conditions. Supplementation of PDA positively modulates ruminal fermentation under normal ruminal pH conditions.