Bacterial Motility

Abstract

Within a given bacterial "sp.," carefully studied and delimited by cultural and agglutination absorption tests (E.O.J.), different degrees of "motility" exist. Some strains, under ordinary conditions of cultivation, consist practically entirely of motile cells; others show no motility in hanging drop or in semisolid media, and no flagellated cells can be found in stained films. Non-motile strains of spp. predominantly motile are probably more common than generally supposed. 4 of about 41 strains of Salmonella schott-mulleri examined remained consistently non-motile for several yrs. In general, the proportion of motile cells in a given strain remains fairly constant when particular attention is given to conditions of growth and testing. However, certain strains may show considerable variation in proportion of motile cells, even when cultures are maintained and handled as uniformly as possible. Environmental conditions affect motility in some strains; one actively motile when grown at 22[degree] C. may be practically non-motile at 37[degree]; the motility of other strains remains apparently uninfluenced by temp. changes. Motility is not a character for exact delimitation of spp. or varieties. Standard cultural characters and bio-chemical reactions do not appear to be correlated with presence or absence of motility.