Abstract
Mycobacterium gilvum PYR-GCK, a pyrene degrading bacterium, has been the subject of functional studies aimed at elucidating mechanisms related to its outstanding pollutant bioremediation/biodegradation activities. Several studies have investigated energy production and conservation in Mycobacterium, however, they all focused on the pathogenic strains using their various hosts as induction sources. To gain greater insight into Mycobacterium energy metabolism, mRNA expression studies focused on respiratory functions were performed under two different conditions using the toxic pollutant pyrene as a test substrate and glucose as a control substrate. This was done using two transcriptomic techniques: global transcriptomic RNA-sequencing and quantitative Real-Time PCR. Growth in the presence of pyrene resulted in upregulated expression of genes associated with limited oxygen or anaerobiosis in M.gilvum PYR-GCK. Upregulated genes included succinate dehydrogenases, nitrite reductase and various electron donors including formate dehydrogenases, fumarate reductases and NADH dehydrogenases. Oxidative phosphorylation genes (with respiratory chain complexes I, III –V) were expressed at low levels compared to the genes coding for the second molecular complex in the bacterial respiratory chain (fumarate reductase); which is highly functional during microaerophilic or anaerobic bacterial growth. This study reveals a molecular adaptation to a hypoxic mode of respiration during aerobic pyrene degradation. This is likely the result of a cellular oxygen shortage resulting from exhaustion of the oxygenase enzymes required for these degradation activities in M.gilvum PYR-GCK.
Highlights
Respiration is a fundamental process in all living organisms, whether aerobic or anaerobic
Relative expression ratios were derived by comparing mRNA abundance levels in cells grown in pyrene substrate relative to mRNA levels in glucose grown cells
Growth on pyrene resulted in considerable changes in the transcription profile versus the glucose grown reference across all Clusters of Orthologous Groups (COGs), the most significant changes primarily involved the genes which function in energy metabolism and pyrenesubstrate metabolism (Table 2)
Summary
Respiration is a fundamental process in all living organisms, whether aerobic or anaerobic. Extreme respiratory flexibility exists in bacteria because they have a vast range of electron acceptors, conferring upon them the ability to colonize many of earth’s habitats including the most hostile micro-oxic and anoxic environments [1] In mycobacteria, this flexible respiratory ability has been reported [2] and attributed to the presence of genes responsible for ATP generation by oxidative phosphorylation (Ubiquinone cytochrome b reductase complex and cytochrome c oxidase) and to genes encoding anaerobic terminal electron acceptors such as nitrate reductase, fumarate reductase and nitrite reductase. This flexible respiratory ability has been reported [2] and attributed to the presence of genes responsible for ATP generation by oxidative phosphorylation (Ubiquinone cytochrome b reductase complex and cytochrome c oxidase) 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. Some non-pathogenic strains perform unique activities including biodegradation and bioremediation of toxic pollutants [5]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call