Wikipedia
Ruminococcus
Ruminococcus is a genus of bacteria in the class Clostridia. They are anaerobic, Gram-positive gut microbes. One or more species in this genus are found in significant numbers in the intestines of humans. The type species is R. flavefaciens. As usual, bacteria taxonomy is in flux, with Clostridia being paraphyletic, and some erroneous members of Ruminococcus being reassigned to a new genus Blautia on the basis of 16S rRNA gene sequences.
One of the most highly cited papers involving the genus Ruminococcus is a paper describing interspecies hydrogen transfer between Ruminococcus albus and Wolinella succinogenes.