The HcaR regulatory protein of Photorhabdus luminescens affects the production of proteins involved in oxidative stress and toxemia.
Comparison of the proteomes of wild-type Photorhabdus luminescens and its hcaR derivative, grown in insect hemolymph, showed that hcaR disruption decreased the production of toxins (tcdA1, mcf, and pirAB) and proteins involved in oxidative stress response (SodA, AhpC, Gor). The disruption of hcaR did not affect growth rate in insects, but did delay the virulence of P. luminescens in Bombyx mori and Spodoptera littoralis larvae. This delayed virulence was associated with a lower toxemia rather than delay in bacteremia. The disruption of hcaR also increased bacterial sensitivity to hydrogen peroxide. A sodA mutant and an hcaR mutant had similar phenotypes in terms of sensitivity to hydrogen peroxide, virulence, toxin gene expression, and growth rate in insects. Thus, the two processes affected by hcaR disruption - toxemia and oxidative stress response - appear to be related. Besides, expression of toxin genes tcdA1, mcf, and pirAB was decreased by paraquat challenge. We provide here the first demonstration of the importance of toxemia for P. luminescens virulence. Our results also highlight the power of proteomic analysis for detecting unexpected links between different, concomitant processes in bacteria.
Chalabaev
Sabina
S
Unité de Génétique des Génomes Bactériens (URA2171), Institut Pasteur, Paris, France.
Turlin
Evelyne
E
Charles
Jean-François
JF
Namane
Abdelkader
A
Pagès
Sylvie
S
Givaudan
Alain
A
Brito-Fravallo
Emma
E
Danchin
Antoine
A
Biville
Francis
F
D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism; D012831:Bombyx / Q000187:drug effects / Q000382:microbiology; D002374:Catalase / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007814:Larva / Q000187:drug effects / Q000382:microbiology; D009154:Mutation / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects; D010269:Paraquat / Q000494:pharmacology; D020637:Photorhabdus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D018411:Spodoptera / Q000187:drug effects / Q000382:microbiology; D014115:Toxemia / Q000382:microbiology*; D014774:Virulence / Q000187:drug effects
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D006861:Hydrogen Peroxide; D002374:Catalase; D010269:Paraquat