Characterization of primary and secondary forms of Xenorhabdus luminescens strain Hm

Abstract

Cultures of the primary form of Xenorhabdus luminescens strain Hm gave rise to secondary forms after prolonged static incubation in two broth media. The secondary forms were deficient in pigmentation and extracellular antibiotic, protease and lipase activities, and were about 100-fold less luminous than the primary form in vivo. Secondary forms isolated on two separate occasions from two different media were identical in their deficiencies. Cultures of the secondary form in defined broth media produced no detectable secondary metabolites, unlike the primary form, and grew more rapidly than the primary form. A protocol for screening primary cultures of X. luminescens for secondary forms is presented.