title: Effect of nitrogen source on growth and trichloroethylene degradation by methane-oxidizing bacteria.
abstract: The effect of nitrogen source on methane-oxidizing bacteria with respect to cellular growth and trichloroethylene (TCE) degradation ability were examined. One mixed chemostat culture and two pure type II methane-oxidizing strains, Methylosinus trichosporium OB3b and strain CAC-2, which was isolated from the chemostat culture, were used in this study. All cultures were able to grow with each of three different nitrogen sources: ammonia, nitrate, and molecular nitrogen. Both M. trichosporium OB3b and strain CAC-2 showed slightly lower net cellular growth rates and cell yields but exhibited higher methane uptake rates, levels of poly-beta-hydroxybutyrate (PHB) production, and naphthalene oxidation rates when grown under nitrogen-fixing conditions. The TCE-degrading ability of each culture was measured in terms of initial TCE oxidation rates and TCE transformation capacities (mass of TCE degraded/biomass inactivated), measured both with and without external energy sources. Higher initial TCE oxidation rates and TCE transformation capacities were observed in nitrogen-fixing mixed, M. trichosporium OB3b, and CAC-2 cultures than in nitrate- or ammonia-supplied cells. TCE transformation capacities were found to correlate with cellular PHB content in all three cultures. The results of this study suggest that the nitrogen-fixing capabilities of methane-oxidizing bacteria can be used to select for high-activity TCE degraders for the enhancement of bioremediation in fixed-nitrogen-limited environments.
authors.affiliation: Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, California 94720-1710, USA.
authors.forename: K H
authors.initials: KH
authors.lastname: Chu
authors.forename: L
authors.initials: L
authors.lastname: Alvarez-Cohen
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001673:Biodegradation, Environmental; D006885:Hydroxybutyrates / Q000032:analysis; D008697:Methane / Q000378:metabolism*; D008772:Methylococcaceae / Q000254:growth & development* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009591:Nitrogenase / Q000378:metabolism; D010084:Oxidation-Reduction; D011091:Polyesters / Q000032:analysis; D014241:Trichloroethylene / Q000378:metabolism*; D000094122:Polyhydroxybutyrates
chemical_list: D000641:Ammonia; D006885:Hydroxybutyrates; D008697:Methane; D009566:Nitrates; D009584:Nitrogen; D009591:Nitrogenase; D011091:Polyesters; D014241:Trichloroethylene; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates