An investigation of the aerobic microbial degradation of sulfur, nitrogen, and oxygen heterocycles by three local marine bacterial consortia

Meade, J. D. (1996) An investigation of the aerobic microbial degradation of sulfur, nitrogen, and oxygen heterocycles by three local marine bacterial consortia. Masters thesis, Memorial University of Newfoundland.

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Abstract

Bacterial samples were collected from three marine beaches in coastal Newfoundland 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 degrade sulfur heterocycles (benzothiophene: BT, 3-methyl-benzothiophene: 3-MBT, and dibenzothiophene: DBT), a nitrogen heterocycle (carbazole: CARB), and an oxygen heterocycle (dibenzofuran: DBF). Incubations were carried out at an optimum temperature for culture (25°C) and at a temperature more typical of a northern environment (4°C). Degradation of the compounds was determined using gas chromatography-mass spectroscopy (GC-MS) and degradation products were identified using GC-MS and Fourier transform infrared spectroscopy (FTIR). Bacterial growth was monitored using optical density measurements to determine the dry weight (μg) of cells/mL and the number of colony forming units/mL (CFU/mL). The 2-ringed heterocycles were degraded faster and to a greater extent than the 3-ringed compounds. Degradation 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 degradability at either incubation temperature. There was a significant difference in degradation of the compounds at the two incubation temperatures as biodegradation was 3 to 5 times greater at 25°C than at 4°C. Statistical examination revealed that no one culture demonstrated a significantly greater ability to degrade the 5 heterocycles studied which means that the bacterial consortium isolated from a beach in Bonne Bay, NF., where the sediments exhibited no visible signs of hydrocarbon contamination, demonstrated the ability to degrade the heterocyles as efficiently as bacterial communities from visibly contaminated soils at Come by Chance and Port aux Basques, NF. This study represents the first comprehensive investigation of the ability of local bacteria to biodegrade a range of aromatic compounds. It provides a preliminary understanding of the fate of aromatic compounds in sediments, in terms of their half-life versus environmental temperature.

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