Submitted to: Nematropica
Publication Type: Abstract Only
Publication Acceptance Date: July 11, 1996
Publication Date: N/A
The entomopathogenic nematodes Heterorhabditis spp. and Steinernema carpocapsae contain the insect-killing bacterial symbionts Photorhabdus luminescens and Xenorhabdus nematophilus, respectively. Primary and secondary phase variants of P. luminescens Hm and Xenorhabdus nematophilus N2-4 were grown at 18 C and 28 C from 24 to 96 hours. At each temperature and culture period, the fatty acid compositions were determined by gas-liquid chromatography. The proportions of the fatty acids 16:1 (carbon atoms: number of double bonds) and 18:1 generally were higher in primary phase variants of P. luminescens grown at 18 C than at 28 C. Prolonged culture at 18 C caused the level of 18:1 to fall and reach that observed at 28 C. The ratio of saturated to unsaturated fatty acids rose with prolonged culture times in both phase variants of each species. When grown at 18 C, the proportion of 16:1 in X. nematophilus was lower than in P. luminescens; the patterns of temperature-induced changes were similar in each species. Xenorhabdus nematophilus contained a greater percentage of short-chain fatty acids (i.e., chain length <14.0) than P. luminescens. The results reflect substantial differences in lipid metabolism between the two bacterial symbionts.