The Swarmers of Bacillus cereus

摘要

SUMMARY The production of swarmers by Bacillus cereus occurs naturally, especially in the case of ‘mycoides’ (i.e. morphologically rough) variants, but can also be induced by growth on media of low nitrogen content containing low concentrations of basic dyes. Very small coccobacilli, usually with one or two polar flagella, are released from the interior of the cells of the mother bacillus. The swarmers are Gram-negative or weakly Gram-positive. On further growth, or on subculture, they increase in size, and may simulate typical Gram-negative bacteria, or in some cases resemble granular, Gram-positive corynebacteria or mycobacteria. Growth of isolated swarmers is extremely slow. On continued subculture, a proportion of strains gradually revert to a Bacillus-like form, complete with heat-resistant endospore. Certain implications of this phenomenon are discussed.