Alternative oxidase (AOX) is a heme-independent terminal oxidase present in the respiratory chains of all plants, as well as in certain fungi, protists, animals, and bacteria. Unlike other respiratory oxidases, AOX does not directly contribute to the generation of a proton motive force. With the exception of thermogenic plants, where AOX is used to generate heat during flowering, its function is uncertain, although in eukaryotes it may contribute to metabolic homeostasis, protection from oxidative stress, or virulence. The role of alternative oxidase in bacterial physiology is unclear. A recent survey of the sequence databases revealed numerous bacteria and marine metagenomic samples whose genomes encode an AOX-like protein. A model organism for studying the role of AOX in bacterial physiology is Vibrio fischeri, a bioluminescent marine bacterium that forms a symbiotic relationship with the Hawaiian bobtail squid. In V. fischeri, microarray and reporter assay results have identified a link between aox gene expression levels and nitric oxide (NO). The overall goal of the research is to investigate the physiological link between AOX and NO. First, quantitative PCR will be used to assess NO-induced changes in aox transcript levels, and second, the effect of NO on the function of terminal respiratory oxidases in V. fischeri will be investigated. This work will provide novel information related to the function of AOX in bacterial physiology, an area that is largely unexplored, but has implications for understanding bacterial contribution to marine ecosystems.
The studies will provide a foundation for future exploration of the role of AOX in diverse bacteria and ultimately a better understanding of the link between bacterial respiration and ecosystem function. In addition, training opportunities will be provided for one graduate and two undergraduate students in basic microbiological techniques, molecular biology, bacterial physiology, and related instrumentation techniques.
