Proteomic Investigation of Photorhabdus Bacteria for Nematode-Host Specificity

Abstract

Majority of animals form symbiotic relationships with bacteria. Based on the number of bacterial species associating with an animal, these symbiotic associations can be mono-specific, relatively simple (2-25 bacterial species/ animal) or highly complex ([10 2 -10 3 bacterial species/animal). Photorhabdus (family-Enterobacteriaceae) forms a mono-specific symbiotic relationship with the entomopathogenic nematode Heterorhabditis. This system provides a tractable genetic model for animal-microbe symbiosis studies. Here, we investigated the bacterial factors that may be responsible for governing host specificity between nematode and their symbiont bacteria using proteomics approach. Total protein profiles of P. luminescens ssp. laumondii (host nematode-H. bacteriophora) and P. luminescens ssp. akhurstii (host nematode-H. indica) were compared using 2-D gel electrophoresis, followed by identification of differentially expressed proteins by MALDI-TOF MS. Thirty-nine unique protein spots were identified -24 from P. luminescens ssp. laumondii and 15 from P. luminescens ssp. akhurstii. These included proteins that might be involved in determining host specificity directly (for e.g. pilin FimA, outer membrane protein A), indirectly through effect on bacterial secondary metabolism (for e.g. malate dehydrogenase Mdh, Pyruvate formate-lyase PflA, flavo protein WrbA), or in a yet unknown manner (for e.g. hypothetical proteins, transcription regulators). Further functional validation is needed to establish the role of these bacterial proteins in nematode-host specificity.

Discovery of a Highly Virulent Strain of Photorhabdus luminescens ssp. akhurstii from Meghalaya, India

“…In order to answer this question, the genetic variance of the toxins, and whether this variance can make a toxin protein hyper-or hypotoxic must be investigated in addition to the toxin expression patterns. Our study identified Photorhabdus 'virulence contrasts' which may be genetically probed using genomic or proteomic approaches to answer these questions, as was done for determining host specificity using proteomics approach [22]. In summary, we discovered a highly virulent strain of P. luminescens ssp.…”