Effects of bacterial age and method of culture on the interaction of xenorhabdus nematophilus(enterobacteriaceae) with hemocytes of nonimmune galleria mellonella(insecta) larvae.

Abstract

Two strains, E4 and E7 of Xenorhabdus nematophilus were used to examine the effect of bacterial age and culture method on the physicochemical properties of the bacteria, the production of flagella, fimbriae, and outer membrane proteins, and subsequently, the adhesion of the bacteria to hemocytes of the insect Galleria mellonella. The patterns of removal of the bacteria from the hemolymph in vivo mediated by the hemocytes varied with the bacterial strain, age and culture method. The cells of both strains in the stationary phase in shaken culture tubes and flasks were more extensively removed by nodule formation than were bacteria in the early and late exponential growth phases. The level of granular cells with adhering bacteria in the hemocyte monolayers in vitro increased with increasing bacterial age for both strains. The in vivo and in vitro hemocyte responses were independent of bacterial hydrophobicity and electrostatic charge but were correlated with bacterial viability. Bacterial metabolites released into culture media did not affect the relationship between bacterial viability and hemocyte contact. Bacterial surface features influenced hemocyte responses. The glycocalyx did not mediate adhesion to hemocytes.