Date of Award

Winter 2009

Project Type


Program or Major


Degree Name

Master of Science

First Advisor

Louis S Tisa


The entomopathogenic nematode Heterorhabditis bacteriophora forms a specific association with its bacterial partner Photorhabdus temperata. The objective of this study was to identify genes involved in insect pathogenesis. Previously we generated a bank of 10,000 transposon mutants and identified 86 motility mutants and 11 calcofluor-binding mutants. The purpose of these experiments was to determine the effects of these defects on bacterial pathogenesis and mutualism. An insect mortality screen with host-model, Galleria mellonella, initially identified 14 mutants with altered insect pathogenesis. Four mutants were confirmed including one (UNH5832) with an enhanced pathogenesis response compared to the parental wild-type, while three other mutants (UNH1307, UNH6441, UNH2033) exhibited a delayed response that was not related to growth rate. These verified mutants include 3 defective motility mutants and one calcofluor-binding mutant. Genetic complementation of UNH1307 proved RNase II to have pleiotropic effects in P. temperata , including the regulation of virulence and motility.