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Title: An investigation into the role of iron homeostasis during the pathogenic and mutualistic interactions of Photorhabdus
Author: Watson, Robert James
ISNI:       0000 0001 2452 2215
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2007
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Photorhabdus spp. is a genus of bacteria found colonising the gut of a specialised stage ofthe nematode, Heterorhabditis, called the infective juvenile (IJ). The IJ is a free-living stage of the nematode that seeks out and infects insect larvae. Once inside the insect the Us release Photorhabdus into the hemolymph where the bacteria rapidly proliferate, killing the insect within 48-72h. The nematodes grow and reproduce in the insect cadaver by feeding on the Photorhabdus biomass. Photorhabdus participates in both pathogenic and mutualistic interactions within its natural lifecycle and this study set out to identify the role of iron within the lifecycle. The importance of iron acquisition' has been demonstrated for many important pathogens, however its role in beneficial interactions has not been so well studied. This study has shown that exbD mediated iron uptake is responsible for full virulence and symbiosis in P. temperata KI22 and is required for virulence in P. luminescens TIOl. However the TTOI exbD mutant was able to support nematode growth and development suggesting that the requirement for iron uptake was different in different bacteria-nerpatode complexes. Genes predicted to be involved in iron acquisition were identified in the sequenced genome of TTOI and these genes were deleted. However none of these mutants had any defect on either pathogenicity or mutualism. Nonetheless the addition of low levels of the iron chelator 2,2'-dipyridyl to the growing Photorhabdus bacteria resulted in a complete absence of nematode growth and development suggesting that iron levels are critical for nematode development. Proteomic analysis ofPhotorhabdus grown under these conditions has revealed the presence of iron regulated proteins which are potentially involved in the interaction with the nematode.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available