LEPTOSPIRAL COLONIAL MORPHOLOGY.

Stalheim, O. H. V. (University of Wisconsin, Madison) and J. B. Wilson. Leptospiral colonial morphology. J. Bacteriol. 86:482-489. 1963.-A sequence of apparent colonial types was observed with colonies of Leptospira pomona, L. canicola, L. icterohaemorrhagiae, and L. grippotyphosa in agar medium. Although some colonies of these serotypes had a different appearance initially, they eventually developed the mature or final appearance characteristic of the serotype. Colonies of freshly isolated, virulent cultures of L. pomona, L. canicola, and L. icterohaemorrhagiae were similar in appearance to colonies of avirulent strains of the same serotype. Additional studies of three stable and distinct colonial types of a laboratory strain of L. autumnalis revealed no differences in antigenicity, catalase activity, or mouse infectivity; however, differences in susceptibility to lysis by oleic acid were found. Although the colonial variants were stable during several in vitro variations, including growth in the presence of homologous antiserum and mutation to growth in a chemically characterized medium, rapid dissociation in vivo was found.