The Selective Culture and Enrichment of Major Rumen Bacteria on Three Distinct Anaerobic Culture Media

Ruminants play an important part in global food security, but also emit methane, which contributes to global warming. Rumen microbes strongly influence the energy retention efficiency from the host's plant-based diet and produce methane as a by-product. While thousands of novel microbial genomes have been assembled from metagenomic sequence data, their culturability is ill-defined. Here, different media (Med10, Med2, and MedTC) were used to isolate co-cultures of microbes from rumen fluid. Thirty-four34 OTUs were identified belonging to the phyla Bacillota (75.28% ± 6.34%), Bacteroidota (19.99% ± 4.85%), Pseudomonadota (2.46% ± 2.01%), and Actinomycetota (2.09% ± 1.07%). The most abundant genera were Selenomonas (28.08% ± 11.71%), Streptococcus (22.67% ± 6.06%), Prevotella (18.71% ± 4.02%), and unclassified Lachnospiraceae (11.50% ± 2.54%), and31 and 31 significantly enriched on at least one medium, with each medium successfully culturing a distinct range of microbes. The composition of the source rumen fluid was vastly different tofrom those cultured. Bacteroidota (52.53% ± 5.10%) predominated, with Bacillota (41.00% ± 3.96%), Methanobacteriota (5.12% ± 1.94%), Pseudomonadota (1.22% ± 0.78%), and Actinomycetota (0.12% ± 0.08%) comprising the rest. The most abundant genera were Prevotella (29.13% ± 4.16%), Butyrivibrio (18.21% ± 2.08%), Succiniclasticum (15.57% ± 5.03%), unclassified Bacteroidetes (13.91% ± 1.67%), and unclassified Prevotellaceae (9.50% ± 2.01%). These data further emphasiseemphasize the importance of using defined media to select for different microbial taxa. This is essential to understand the complex workings of the rumen microbes to enhance digestion efficiency and reduce the loss of energy that could potentially be utilisedutilized by the host.