Immune responses of the insect Manduca sexta towards the bacterium Photorhabdus luminescens

  • Peter Millichap

Student thesis: Doctoral ThesisPhD


The Gram-negative bacterium Photorhabdus luminescens is a pathogen of insects. It is able to secrete a variety of toxins and effectors against its host in order to escape its immune defences. The model insect Manduca sexta is able to mount a variety of humoral and cellular responses against pathogen attack. Ultimately these prove ineffective against P. luminescens. The pre-treatment of M. sexta with Escherichia coli provides protection against the pathogenesis of P. luminescens. Here, I use RNA interference and Fluorescence-assisted cell sorting techniques to investigate interactions between pathogen and host to further elucidate the roles of various host factors in mounting the immune response. I also investigate the nutrient requirements of the bacteria for pathogenesis. I show data that peptidoglycan recognition protein (PGRP) is essential for the up-regulation of antimicrobial peptides, an important immune defence. I also show that P. luminescens has a requirement for two types of iron during pathogenesis of M. sexta. And lastly I show that P. luminescens is able to avoid phagocytosis, another important immune defence.
Date of Award1 Sept 2008
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorStuart Reynolds (Supervisor)


  • transferrin
  • peptidoglycan recognition protein
  • Photorhabdus luminescens
  • Manduca sexta
  • ferritin
  • FACS
  • fluorescent-assisted cell sorting
  • Insect immunity
  • RNA interference

Cite this