Comparisons of bacterial and archaeal communities in the rumen and a dual-flow continuous culture fermentation system...

Dual-flow continuous culture (CC) fermenters are commonly used to study rumen fermentation in vitro. Research using culture-based and oligonucleotide techniques has shown that certain microbial populations within fermenters may be maintained at abundances similar to those observed in vivo. In this study, bacterial and archaeal communities in the rumen of dairy cattle and in a dual-flow CC fermentation system were compared using high-throughput amplicon sequencing targeting the V4 hypervariable region of 16S rRNA. We hypothesized that the in vitro system harbored a comparable bacterial and archaeal community to that observed in the rumen. Members of the Bacteroidetes and Firmicutes made up the 2 most abundant phyla in the rumen, inoculum, and fermenters and did not differ among sample types (P > 0.10). Similarly, Prevotellaceae, the most abundant family in all 3 sample types, did not differ based on source (P = 0.80). However, beta diversity analyses revealed that bacterial and archaeal communities differed between fermenters and rumen samples (P ≤ 0.001), but fermenter bacterial and archaeal communities stabilized by day 4 of each period. While the overall bacterial and archaeal community differs between natural rumens and those detected in in vitro fermenter systems, several prominent taxa were maintained at similar relative abundances suggesting that fermenters may provide a suitable environment in which to study shifts among the predominant members of the microbial community.