Purification and characterization of some hydrolases secreted by Photorhabdus luminescens nssp. MN7

Abstract

Photorhabdus is a genus of enterobacterial symbionts of Heterorhabditis, a genus of entomopathogenic nematodes. These two associated organisms are capable of infecting a wide range of arthropods, from insects to isopods and even ticks. The genome of Photorhabdus luminescens TT01 has been completely sequenced and so are the genomes of two other species of the genus, P. asymbiotica and P. temperata. It is anticipated that approximately 6% of the genome of P. luminescens TT01 is composed of genes for the production of secondary metabolites, almost double the 3.8% found for Streptomyces, a model for the study of this class of metabolites. Among the enzymes secreted by P. luminescens TT01, there is PrtA, a metalloprotease that belongs to the subfamily of serralysins and PRTs, a protease capable of inducing a strong melanization response in infected insects. Lipases also represent an important class of secreted proteins. TT01 encodes at least ten triacylglycerol lipases, and phospholipases A and D. There are predicted genes encoding chitinases in the genome of P. luminescens TT01. This project aims to advance the characterization of MN7 initiated during our undergraduate internship, extending the objectives to enzymes involved in bioconversion of the insect host corpse and protecting the bacteria that thrive there. To do this we intend to detect, isolate and characterize some hydrolases secreted in vitro by isolated MN7 new subspecies of the genus, Photorhabdus luminescens nssp. In addition we intend to further characterize the main proteolytic activity, as detected in preliminary zymograms and produce a monospecific antiserum for this hydrolase.