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 kinase sensor protein, EnvZ, of Xenorhabdus nematophilus, affected the production of several outer membrane proteins (Opns). X. nematophilus produced five major Opns during exponential growth. Insertional inactivation of envZ led to a decrease in the production of OpnP, the OmpF-like pore-forming protein which constitutes approximately 50% of the total outer membrane protein in X. nematophilus. OpnA production was also reduced, while the remaining Opns were produced normally. During the transition 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 at markedly reduced levels. These results suggest that EnvZ was required for the high-level production of OpnP during exponential growth and may be involved in the production of OpnB, OpnS, and OpnX during stationary-phase growth. We also show that ANT1 was more pathogenic than the wild-type strain when as few as five cells were injected into the hemolymph of the larval stage of the tobacco hornworm (Manduca sexta). The 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.