H-NOX–mediated nitric oxide sensing modulates symbiotic colonization by Vibrio fischeri

• DOI: 10.1073/pnas.1003571107
• Publication Date: 2010-04-20T03:40:15Z
• Authors: Yanling Wang; Yann S. Dufour; Hans K. Carlson; Timothy J. Donohue; Michael A. Marletta; Edward G. Ruby
• Keywords: Hemin

The bioluminescent bacterium Vibrio fischeri initiates a specific, persistent symbiosis in the light organ of squid Euprymna scolopes. During early stages colonization, V. is exposed to host-derived nitric oxide (NO). Although NO can be both an antimicrobial component innate immunity and key signaling molecule eukaryotes, potential roles beneficial host-microbe associations have not been described. hnoX encodes heme NO/oxygen-binding (H-NOX) protein, member family bacterial NO- and/or O(2)-binding proteins unknown function. We hypothesized that H-NOX acts as sensor involved regulating symbiosis-related genes colonization. Whole-genome expression studies identified 20 were repressed H-NOX-dependent fashion. Ten these, including hemin-utilization genes, promoter with putative ferric-uptake regulator (Fur) binding site. As predicted, presence NO, wild-type grew more slowly on hemin than deletion mutant. Host-colonization showed mutant was also 10-fold efficient initially colonizing host wild type; similarly, mixed inoculations, it outcompeted strain by average 16-fold after 24 h. However, excess or iron reversed this dominance. advantage iron-limited light-organ tissues caused, at least part, its greater ability acquire hemin. Our data suggest normally senses host-generated signal through H-NOX(Vf) modulates uptake capacity during symbiosis.