Variants of Serratia marcescens induced by freeze-drying.

Unusually high numbers of pigmentless variants and sectored colonies in cultures of lyophylized Serratia marcescens are reported. Clonal analyses of sectored colonies show the presence of unstable bacteria that continue to sector again when plated. Further analysis of pigmentless variants suggest that pigment formation, oxygen uptake, and the production of an inducible protease are affected.