Effects of associated bacteria on the pathogenicity and reproduction of the insect-parasitic nematode Rhabditis blumi (Nematoda: Rhabditida) |
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Authors: | Park Hae Woong Kim Yong Ook Ha Jae-Seok Youn Sung Hun Kim Hyeong Hwan Bilgrami Anwar L Shin Chul Soo |
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Affiliation: | Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Shinchon-dong, Seodaemun-gu, Seoul 120-749, South Korea. |
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Abstract: | Three bacteria, Alcaligenes faecalis , Flavobacterium sp., and Providencia vermicola , were isolated from dauer juveniles of Rhabditis blumi . The pathogenic effects of the bacteria against 4th instar larvae of Galleria mellonella were investigated. Providencia vermicola and Flavobacterium sp. showed 100% mortality at 48?h after haemocoelic injection, whereas A. faecalis showed less than 30% mortality. Dauer juveniles showed 100% mortality against G. mellonella larvae, whereas axenic juveniles, which do not harbor associated bacteria, exhibited little mortality. All of the associated bacteria were used as a food source for nematode growth, and nematode yield differed with bacterial species. Among the bacterial species, P.?vermicola was most valued for nematode yield, showing the highest yield of 5.2?× 10(4) nematodes/mL in the plate. In bacterial cocultures using two of the three associated bacteria, one kind stimulated the other. The highest total bacterial yield of 12.6?g/L was obtained when the inoculum ratio of P. vermicola to A. faecalis was 10:1. In air-lift bioreactors, the nematode growth rate increased with an increasing level of dissolved oxygen. The maximum nematode yield of 1.75?× 10(5)?nematodes/mL was obtained at 192?h with an aeration rate of 6 vvm. |
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