Cellular energy, synthesized and released in the form of ATP, is produced from an electrochemical gradient generated via these electron transfer processes. Extreme respiratory flexibility exists in bacteria because they have a vast range of electron acceptors,STK16-IN-1 conferring upon them the ability to colonize many of earth’s habitats including the most hostile micro-oxic and anoxic environments. In mycobacteria, this flexible respiratory ability has been reported and attributed to the presence of genes responsible for ATP generation by oxidative phosphorylation and to genes encoding anaerobic terminal electron acceptors such as nitrate reductase, fumarate reductase and nitrite reductase. This group of aerobes is unique in that they have characteristically strong cell envelopes which give them the ability to survive in stressful environments. In some pathogenic mycobacterial species, the cell wall is reported to aid in protective invasion of their hosts and resistance to antibiotics. Some non-pathogenic strains also perform unique activities including biodegradation and bioremediation of toxic pollutants. Mycobacterium gilvum PYR-GCK was isolated from the sediment of the Grand Calumet River in Northwestern Indiana based on its ability to utilize pyrene,SW044248 a toxic polycyclic hydrocarbon, as a growth substrate. Many reports list the presence of atmospheric oxygen as important for hydrocarbon degradation while others have demonstrated the possibility of anaerobic hydrocarbon degradation. Widdel and Rabbus showed that the biochemical mechanisms of aerobic and anaerobic hydrocarbon degradation are completely different. M.gilvum PYR-GCK has been cultivated aerobically in studies evaluating the molecular events occurring during pyrene degradation and in studies aimed at the development of more effective bioremediation strategies. The results revealed links between metabolic pathways and respiratory mechanisms. In the current study, a more in-depth analysis of the respiratory activities of M.gilvum PYR-GCK was initiated, using pyrene and glucose as test and control substrates respectively. We utilized a gene expression study to evaluate genetic biomarkers for respiratory processes in M.gilvum PYR-GCK.