Aerobic co-metabolism of sulfur, nitrogen and oxygen heterocycles by three marine bacterial consortia

Bacterial samples were collected from three marine beaches in coastal Newfoundland, Canada, and enriched by growth on 1-methylnaphthalene. The most prominent bacterial cell type for each consortium was isolated in a serial dilutions test, and a substrate utilization profile was obtained for each using the Biolog MicroStation System. Each bacterial community was tested for its ability to co-metabolize sulfur heterocycles (benzothiophene: BT, 3-methylbenzothiophene: 3-MBT, and dibenzothiphene: DBT), a nitrogen heterocycle (carbazole: CARB), and an oxygen heterocycle (dibenzofuran: DBF). Co-metabolism of the starting material was determined using gas chromatography-mass spectroscopy (GC-MS), and formation of products was investigated by GC-MS and Fourier transform infrared (FTIR) spectroscopy. Bacterial growth was monitored turbidimetrically to determine the dry weight (microgram) of cells/ml. The 2-ringed heterocycles were co-metabolized faster and to a greater extent than the 3-ringed compounds. Co-metabolism of BT was not statistically different from that for 3-MBT and, likewise, a comparison of the 3-ringed heterocycles showed no significant differences in degradation rates. Statistical examination showed that no one culture demonstrated a significantly greater ability to co-metabolize the heterocycles studied. This study represents the first comprehensive investigation of the ability of local bacteria to co-metabolize a range of aromatic compounds and provides a preliminary understanding of their fate in sediments should contamination by these compounds occur.