Motility as a Factor in Bowel Colonization by Roseburia cecicola, an Obligately Anaerobic Bacterium from the Mouse Caecum

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Abstract
R. cecicola strain GM is a motile obligate anaerobe that was isolated from mouse cecal mucosa. Strains (25) of motility mutants were obtained from populations of strain GM (wild-type) that had been exposed to UV light. Unlike GM cells, mutant bacteria were non-motile and non-flagellated (Fla-) or migrated slowly or atypically in semi-solid medium. Strain GM and 2 mutant strains, SLS (Fla-) and WES (atypically motile), were used in mouse colonization experiments. In separate experiments, each strain colonized (4.8 .times. 109-1.5 .times. 1010 c.f.u./g cecum) the cecum of germfree mice inoculated intragastrically with pure cultures of the bacteria. In mice mono-associated with either mutant strain, bacteria which were non-motile or atypically motile predominated in their caeca (> 99% of total bacteria recovered). In mice mono-associated with motile cells of strain GM, mutant strains which had lost wild-type motility became predominant in the cecal populations (97% of total bacteria recovered at 48-70 days after inoculation). Mice mono-associated with strain SLS or strain GM were colonized by 1 strain each of Escherichia coli, Candida pintolopesii, a Bacteroides sp. and a Clostridium sp. Most (99%) of the R. cecicola cells recovered from the ceca of these animals had typical wild-type motility. Motility, although not essential for R. cecicola to colonize germfree mice, is apparently advantageous to this bacterium when other microorganisms are present with it in the mouse cecum. Motility may thus be essential for R. cecicola to colonize conventional laboratory mice.