Cyanogenesis by the entomopathogenic bacteriumPseudomonas entomophila

Abstract

To investigate whether the entomopathogenic bacterium Pseudomonas entomophila can synthesize hydrogen cyanide (HCN). Cyanide production was assayed for during the growth of P. entomophila in liquid culture and during colonial growth. Pseudomonas entomophila produced HCN at a concentration of up to 40 micromol l(-1) during growth in liquid cultures and its production was found to be affected by oxygen availability, with levels increasing as the oxygen-transfer coefficient decreased. Pseudomonas entomophila made HCN during colonial growth at levels greater (approximately threefold) than those made by the well studied cyanogenic bacterium Pseudomonas aeruginosa. This study demonstrated unequivocally that P. entomophila can synthesize HCN, placing it among the small number of cyanogenic bacteria. Our data indicate that HCN production in P. entomophila is regulated by oxygen availability. Pseudomonas entomophila was recently identified to be the only pseudomonad that naturally infects and induces lethality of Drosophila melanogaster. The virulence factors which contribute to entomopathogenicity exerted by this species are largely unknown. In this study, we demonstrate that P. entomophila produces HCN, a secondary metabolite implicated in biocontrol properties and pathogenicity exerted by other bacteria.