Nematoxins of microbial origin: Their identification, characterization and development as bio-nematicides ii. Effect of growth conditions on the nematoxicity of bactrial isolates

Effect of growth temperature on nematoxicity of four bacterial isolates (Cultures or CFs) was studied in vitro. In general, 25 and 30° C growth temperature induced maximum nematode mortality. Providencia rittgeri (isolate # 78), P. rittgeri (isolate # 123) and Vibrio sp. (isolate # 84) were equally effective when cultured at a temperature of 25 and 30° C, while Pseudomonas putida (isolate # 113) was more effective when grown at 30° C. Age (24–96 h) of bacterial cultures also influenced their nematoxicity. Lab assays using cultures and Cell-free culture filtrates of 24–96 h revealed that a minimum of 48 h growth was necessary to achieve maximum nematoxicity; this was true for all the four isolates. Bacterial growth media viz., LB, YEPD and TY alone (without bacteria) proved toxic to Meloidogyne javanica J2, more so at higher concentrations. Only NB alone was not lethal to nematodes, hence it was found suitable for growth of all the four isolates for nematoxicity tests.