ROLE OF THE HISTIDINE KINASE, ENVZ, IN THE PRODUCTION OF OUTER-MEMBRANE PROTEINS IN THE SYMBIOTIC-PATHOGENIC BACTERIUM XENORHABDUS-NEMATOPHILUS

We show that inactivation of envZ, the gene encoding the histidine kin ase sensor protein, EnvZ, of Xenorhabdus nematophilus, affected the pr oduction of several outer membrane proteins (Opns), X. nematophilus pr oduced five major Opns during exponential growth, Insertional inactiva tion of envZ led to a decrease in the production of OpnP, the OmpF-lik e pore-forming protein which constitutes approximately 50% of the tota l outer membrane protein in X. nematophilus. OpnA production was also reduced, while the remaining Opns were produced normally, During the t ransition to stationary phase, three new outer membrane proteins, OpnB , OpnS, and OpnX, were induced in the wild-type strain. The envZ-minus strain, ANT1, did not produce OpnB and OpnX, while OpnS was induced a t markedly reduced levels, These results suggest that EnvZ was require d for the high-level production of OpnP during exponential growth and may be involved in the production of OpnB, OpnS, and OpnX during stati onary-phase growth, We also show that ANT1 was more pathogenic than th e wild-type strain when as few as five cells were injected into the he molymph of the larval stage of the tobacco hornworm (Manduca serta). T he larvae died before significant numbers of bacteria were detectable in the hemolymph, These results are discussed in relation to the role of EnvZ in the life cycle of X, nematophilus.