pseudobutyrivibrio pseudobutyrivibrio pseudobutyrivibrio is a gram-negative, anaerobic and non-spore-forming bacterial genus from the family of lachnospiraceae. pseudobutyrivibrio scientific classification domain: bacteria phylum: bacillota class: clostridia order: eubacteriales family: lachnospiraceae genus: pseudobutyrivibriovan gylswyk et al. 1996 type species pseudobutyrivibrio ruminis species p. ruminis p. xylanivorans pseudobutyrivibrio as gram-negative, is in contrast to butyrivibrio, which is gram-positive, as is typical of most bacillota phylum bacteria.