Substrate Utilization by Micrococcus Luteus: Biodegradation of Pyridine for Metabolic Modeling

The bacterium Micrococcus luteus was grown on three substrates: glucose, acetate, and pyridine; all maintained at a molar C: N ratio of 5:1 Optical density, pH measurements, substrate, and ammonium concentrations were monitored at regular intervals. The N-heterocycle pyridine is a by-product of coal gasification and oil shale that has high water solubility and mobility through the soil; leading to surface and groundwater contamination. M. luteus was able to grow on all substrates and riboflavin production was apparent in all treatments. Glucose, the most widely used energy reserve, produced acidic conditions during log phase growth, and supported the most biomass production. Acetate surprisingly produced alkaline conditions during log phase growth. Pyridine was oxidized for energy by M luteus and as the pyridine concentration decreased, the ammonium concentration increased. The ring N was released to the medium as ammonium or incorporated into biomass. M luteus utilized pyridine as a carbon, nitrogen, and energy source similar to glucose and acetate treatments amended with ammonium. The metabolism of N-heterocycles remains poorly understood, but with transcriptomic analysis and metabolic modeling, more information on the metabolic pathways of pyridine degradation can be obtained. More studies of this organism will be necessary to elucidate the degradative pathways for pyridine; which can lead to a better understanding of N-heterocycle-degrading microorganisms