Liquid culture carbon, nitrogen and inorganic phosphate source regulate nematicidal activity by fluorescent pseudomonads in vitro

Aims: The aim of the present investigation was to determine the influence of nutrients on the nematicidal activity by Pseudomonas aeruginosa strain IE-6S(+) and Ps. fluorescens strain CHA0 in vitro. Methods and Results: Culture filtrate of IE-6S(+) and CHA0 obtained from chemically defined medium caused mortality of Meloidogyne javanica juveniles in vitro and that growth medium amended with various C, N or inorganic phosphate (Pi) sources markedly influenced nematicidal activity of the two bacteria. Glycerol (C source), propionate (fatty acid precursor) and L-lysine (N source) enhanced nematicidal activity while glucose (C), L-valine (N) and Pi substantially repressed nematicidal activity of the two bacteria. Conclusion: Liquid culture amendments with various C, N or Pi sources modulate the biosynthesis of nematicidal agents to a different extent in vitro. Significance and Impact of the Study: Developing bacterial strains more responsive to certain environmental signals can be exploited for increased secondary metabolite production in pharmaceutical fermentations and offers new avenues to improve biocontrol.