The role of alternative oxidase in bacterial physiology

Alternative oxidase (AOX) is a respiratory oxidase that was first identified in plants. Unlike the "normal" cytochrome oxidase, AOX does not directly link the reduction of oxygen to the generation of proton motive force (or in other words energy conservation). The best described role for AOX is for heat generation in thermogenic plants, which use the energy produced by AOX to volatilize scent for attracting pollinating insects. This protein is ubiquitous in plants, although the role in non-thermogenic plants is not as clear.

Until recently, it was thought that bacteria did not contain AOX. With the increasing number of microbial genome sequences available, it has become apparent that certain groups of bacteria have members whose genomes do encode AOX. One commonality among bacteria with AOX is that they can be found associated with a marine environment. In addition, analysis of metagenomic datasets from marine environments indicates aox-like genes are in relatively high abundance. Despite its apparently wide distribution in bacteria inhabiting marine surface waters, little is known about the role of this interesting protein in bacterial physiology

Unlike many of the bacteria whose genomes encode AOX, there is a wealth of molecular and genetic tools available for use with V. fischeri, making it an ideal model organism for studying the role of AOX in the respiratory function of bacteria.

The role of energy generation pathways in host-microbe interactions Another research interest is in determining how energy generation pathways (oxidative and/or substrate-level phosphorylation) contribute to the ability of beneficial bacteria to colonize host tissue. We use the symbiotic relationship between V. fischeri and the Hawaiian bobtail squid Euprymna scolopes as a model system for understanding how these bacterial processes contribute to the non-pathogenic colonization of host tissue.

An adult Hawaiian bobtail squid (Euprymna scolopes), that is the symbiotic host of the bioluminescent marine bacterium Vibrio fischeri. [Credit: M. J. McFall-Ngai and E. G. Ruby]

Our current research is focusing on anaerobic respiratory and fermentative pathways in V. fischeri.

Synchronized Swimming Squid Studies (future directions)