Culturing of 'unculturable' rumen bacteria using dilution to extinction and media diversification

Theano Stoikidou, Ziming Wu, Corey Roulston, Jnana Sree Pakalapati, Jack Jordan, Maria Buckland, Katie Lawther, James Pickup, Fernanda Godoy Santos, Linda Oyama, Conrad Ferris, Sharon Huws

Research output: Contribution to conferenceAbstractpeer-review


The rumen represents 80% of the ruminant stomach at maturity and it is a complex, dynamic ecosystem comprising mainly anaerobic bacteria, protozoa, anaerobic fungi, methanogenic archaea, and bacteriophages. These microbes interact with each other and have a symbiotic relationship with the host, providing energy from the breakdown of plant cell wall carbohydrates. The understanding of most microbiomes, including therumen, is hindered by poor culture collections and reduced efforts placed on culturing after the recent boostin the ‘omic’ technologies; leading to an assumption that many microbes are unculturable, when it is recognised that with enhanced effort they could be cultured. In this study, using the dilution to extinction method, cattle and sheep samples were plated onto Bovine Heart Infusion (BHI) medium, Hobson’s M2 medium, and PC basal medium all prepared with and without rumen fluid. Our efforts allowed for the isolation of over 120 ruminal bacteria with profile differences as per medium emphasising the significance of diversification of growth media during isolation. Furthermore, 16S rRNA gene sequencing of the isolates revealed a potent new species of ruminal bacteria; according to the NCBI database, the most closely related species to it is the Parabacteroides goldsteinii with 94.38% identity. Characterisation of this new species further may provide insights into their role in the rumen as well as their importance for the host. Overall, our results allow for an improved understanding of the rumen microbiome as well as new research possibilities on its role/function with respect to animal health,productivity, and sustainability.

Original languageEnglish
Publication statusPublished - 13 Jun 2023
Event13th International Gut Microbiology Symposium 2023 - Aberdeen, United Kingdom
Duration: 13 Jun 202315 Jun 2023


Conference13th International Gut Microbiology Symposium 2023
Country/TerritoryUnited Kingdom
Internet address


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