Purification and characterization of tryptophan and indole-3-acetic acid produced by Serratia marcescens strain MCB associated with Oscheius sp. MCB (Nematoda: Rhabditidae) obtained from South African soil

Abstract

Entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis are lethal to insect pests that attack plants. These EPNs are associated symbiotically with the two enterobacteria Xenorhabdus and Photorhabdus sp., respectively. The bacteria synthesize a range of insecticidal and antimicrobial metabolites which may be useful as agricultural pest control and medical disease control. Recently, EPNs characterization and explanation have been expanded to include genera, Oscheius. We isolated, characterized and identified a symbiotic bacterium and the metabolites it produces. The symbiotic bacterium was isolated from a South African nematode, Oscheius sp. MCB (GenBank accession number: KF684370). The symbiotic bacterium was identified to be a Serratia marcescens strain MCB (GenBank accession number: KF793930). Two metabolites it produces are indole-3-acetic acid and tryptophan, with tryptophan as an aromatic amino acid assumed to be a precursor for indole-3-acetic acid production. From this study it is evident that S. marcescens strain MCB isolated from Oscheius sp. MCB shares similar attributes with Xenorhabdus and Photorhabdus sp., thus its host can be accepted as an EPN. Key words: Entomopathogenic nematodes, Serratia, Oscheius, Xenorhabdus, Photorhabdus.