PhotorhabdusDam methyltransferase overexpression impairs virulence of the nemato-bacterial complex in insects

Abstract

AbstractPhotorhabdus luminescensis an entomopathogenic bacterium found in symbiosis with the nematodeHeterorhabditis. Dam DNA methylation is involved in the pathogenicity of many bacteria, includingP. luminescens,whereas studies about the role of bacterial DNA methylation during symbiosis are scarce. The aim of this study was to determine the role of Dam DNA methylation inP. luminescenssymbiosis withH. bacteriophora. We constructed a strain overexpressingdamby inserting an additional copy of thedamgene under the control of a constitutive promoter in the chromosome ofP. luminescensand then achieved association between this recombinant strain and nematodes. Thedamoverexpressing strain was able to feed the nematodein vitroandin vivosimilarly as a control strain, and to re-associate with Infective Juvenile (IJ) stages in the insect. No difference in the amount of emerging IJs from the cadaver was observed between the two strains. Compared to the nematode in symbiosis with the control strain, a significant increase in LT50was observed during insect infestation with the nematode associated with thedamoverexpressing strain. These results suggest that theP. luminescensDam plays a role in the pathogenicity of the nemato-bacterial complex.