Analysis of factors governing nematode-host specificity in bacterium Photorhabdus

M of animals form symbiotic relationships with bacteria. Some animals partner with a single bacterial symbiont, while other animals symbiose with simple or complex bacterial consortia. The insect parasitic nematode Heterorhabditis lives in mono-specific symbiotic relationship with the enterobacterium Photorhabdus and is a tractable genetic model for the study of animal-microbe relationships. Heterorhabditis-Photorhabdus association is highly species-specific. Present work was undertaken to identify factors which might be involved in the host specificity of the bacterial symbionts Photorhabdus with its nematode partner Heterorhabditis. Total protein profile of 2 Photorhabdus sub-species, P. luminescens subsp. laumondii (isolated from H. bacteriophora) and P. luminescens subsp. akhurstii (isolated from H. indica) was compared by 2D Gel electrophoresis followed by identification of differentially expressed proteins by MALDI-TOF MS. Out of 43 proteins analyzed, 13 unique proteins were identified in P. luminescens subsp. laumondii comprising 2 catalases, 3 ABC-type transporters, 1 translation elongation factor, 1 outer membrane Protein, 1 peptidase,1 chaperon protein, 2 antibiotic synthesis regulators and 2 hypothetical proteins. Remaining 20 were from P. luminescens subsp. akhurstii, showing 2 transcription regulators, 4 dehydrogenases, 2 ABC-type transporter, 1 DNA topoisomerase, 1 catalase, 1 kinase, 2 Tol B (protein import), 2 involved in amino acid synthesis, 2 involved in phosphate biosynthesis and 3 hypothetical proteins. Here we identified some of the proteins that might be involved in nematode-host specificity between Heterorhabditis and Photorhabdus.