Submitted to: American Society of Parasitologists
Publication Type: Abstract only
Publication Acceptance Date: 6/15/1996
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The entomopathogenic nematodes Heterorhabditis spp. and Steinernema carpocapsae contain the insect-killing bacterial symbionts Photorhabdus luminescens and Xenorhabdus nematophilus, respectively. The two bacterial species exist in culture as primary and secondary phase variants, which differ in secretion of metabolic end products and in survival within the nematode digestive system. To determine if these differences result from membrane physical properties, primary and secondary phase variants of P. luminescens Hm and X. nematophilus N2-4 were grown at 18 C and 28 C from 24 to 96 hours. At each temperature and culture period, vesicles were prepared from total lipids extracted from the bacteria. Vesicle membrane fluidity was determined with an electron spin resonance procedure utilizing 5-doxyl-stearic acid as a probe. Vesicles from primary and secondary cultures of both bacterial species grown at 18 C were more ordered than those grown at 28 C. Vesicles from primary cultures of P. luminescens were substantially more ordered than those from secondary cultures. In X. nematophilus, this difference was less conspicuous. At both culture temperatures, membranes from primary cultures of P. luminescens were more ordered than membranes from X. nematophilus. The results reflect interesting biophysical differences between the membranes of the two species.