In bacteria these are a structurally and functionally diverse group of proteins which play important roles in the adaptation of bacteria to grow in different environments. We are using biochemical and molecular genetic approaches to study the multiple terminal oxidases of the opportunistic pathogen Pseudomonas aeruginosa . This bacterium can adapt to infectious situations ranging from the highly oxygenated lungs of cystic fibrosis patients to the low oxygen environment of wound infections. Our aim is to understand the structural, functional and regulatory features of these oxidases to elucidate their roles in the adaptation of P. aeruginosa to different environments. We also have an interest in the part played by DNA topology in the regulation of the genes for bacterial oxidases.
Oxygen presents some bacteria with specific problems.
An example is the agriculturally important, nitrogen-fixing bacterium, Rhizobium . This bacterium infects the roots of leguminous plants, such as peas and beans, forming structures called root nodules in which it fixes atmospheric nitrogen to ammonia, a portion of which is made available to the plant. However, Rhizobium is faced with a dilemma. Nitrogen-fixation requires the large amounts of energy which are provided by oxygen via aerobic respiration, a process which is incompatible with the extreme sensitivity of nitrogen fixation to oxygen. The bacteria have evolved physiological mechanisms which cope with this paradox.