INSERTIONAL INACTIVATION OF GENES ENCODING THE CRYSTALLINE INCLUSION PROTEINS OF PHOTORHABDUS-LUMINESCENS RESULTS IN MUTANTS WITH PLEIOTROPIC PHENOTYPES

The entomopathogenic bacterium Photorhabdus luminescens exhibits phase variation when cultured in vitro. The variant forms of P. luminescens are pleiotropic and are designated phase I and phase II variants. One of the characteristic phenotypes of phase I cells is the production o f two types of intracellular protein inclusions. The genes encoding th e protein monomers that form these inclusions, designated cipA and cip B, were cloned and characterized. cipA and cipB encode hydrophobic pro teins of 11,648 and 11,308 Da, respectively. The deduced amino acid se quences of CipA and CipB have no significant amino acid sequence simil arity to any other known protein but have 25% identity and 49% similar ity to each other, Insertional inactivation of cipA or cipB in phase I cells of P. luminescens produced mutants that differ from phase I cel ls in bioluminescence, the pattern and activities of extracellular pro ducts, biochemical traits, adsorption of dyes, and ability to support nematode growth and reproduction, In general, the cip mutants were phe notypically more similar to each other than to either phase I or phase II variants.