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Roseburia cecicola strain GM is a motile obligate anaerobe that was isolated from mouse caecal mucosa. Twenty-five strains 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 either non-motile and non-flagellated (Fla-) or migrated slowly or atypically in semi-solid medium. Strain GM and two mutant strains, SLS (Fla-) and WES (atypically motile), were used in mouse colonization experiments. In separate experiments, each strain colonized (4.8 X 10(9) to 1.5 X 10(10) c.f.u. per g caecum) the caecum 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 (greater than 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 caecal populations (97% of total bacteria recovered at 48 to 70 days after inoculation). Mice mono-associated with either strain SLS or strain GM were colonized by one strain each of Escherichia coli, Candida pintolopesii, a Bacteroides sp., and a Clostridium sp. Most (99%) of the R. cecicola cells recovered from the caeca 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 micro-organisms are present with it in the mouse caecum. Motility may thus be essential for R. cecicola to colonize conventional laboratory mice.

The excretion of 7 individual 17-oxosteroids and 7 individual corticosteroids in 24 h urine samples from 62 normal infants, children and adolescents, based on an accurate and specific paper chromatographic method for their separation and quantitation, is reported. The excretion of the 11-deoxy-17-oxosteroids gradually increases from 7 years of age and the increase becomes more rapid 2 or 3 years before the clinical signs of puberty appear. The rise continues throughout puberty and beyond it until the adult level is reached. The increase far exceeds that which would be accounted for by the growth of the individual. The increase in the excretion of the 11-oxy-17-oxosteroids with age is much more gradual. Androgens favour the formation of 5α metabolites and the 5α:5β ratio of the total 5α 17-oxosteroids and the total 5β 17-oxosteroids shows a statistically significant increase with age. In addition, a relatively high 5α:5β ratio is noted in male infants, which is likely to be related to their relatively high plasma testosterone levels. The excretion of the 17-hydroxycorticosteroids and the α-ketolic metabolites of cortisol gradually rises with age and correlates with body weight. The α-ketolic metabolites of corticosterone are relatively high in infancy, but after the age of 4 years their excretion also correlates with body weight. An increase in the 5α:5β ratio of allo-THF to THF is noted at puberty similar to that found with the 5α:5β ratios of the 17-oxosteroids.