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Applied and Environmental Microbiology, August 2004, p. 4629-4634, Vol. 70, No. 8
0099-2240/04/$08.00+0 DOI: 10.1128/AEM.70.8.4629-4634.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Department of Environmental Engineering and Science, Clemson University, Clemson, South Carolina 29634,1 Shaw Environmental & Infrastructure, Inc., Stoughton, Massachusetts 02072,2 Westinghouse Savannah River Company, Aiken, South Carolina 29808,3 Lawrence Livermore National Laboratory, Livermore, California 945504
Received 19 January 2004/ Accepted 23 April 2004
Pseudomonas aeruginosa strain NB1 uses chloromethane (CM) as its sole source of carbon and energy under nitrate-reducing and aerobic conditions. The observed yield of NB1 was 0.20 (±0.06) (mean ± standard deviation) and 0.28 (±0.01) mg of total suspended solids (TSS) mg of CM1 under anoxic and aerobic conditions, respectively. The stoichiometry of nitrate consumption was 0.75 (±0.10) electron equivalents (eeq) of NO3 per eeq of CM, which is consistent with the yield when it is expressed on an eeq basis. Nitrate was stoichiometrically converted to dinitrogen (0.51 ± 0.05 mol of N2 per mol of NO3). The stoichiometry of oxygen use with CM (0.85 ± 0.21 eeq of O2 per eeq of CM) was also consistent with the aerobic yield. Stoichiometric release of chloride and minimal accumulation of soluble metabolic products (measured as chemical oxygen demand) following CM consumption, under anoxic and aerobic conditions, indicated complete biodegradation of CM. Acetylene did not inhibit CM use under aerobic conditions, implying that a monooxygenase was not involved in initiating aerobic CM metabolism. Under anoxic conditions, the maximum specific CM utilization rate (k) for NB1 was 5.01 (±0.06) µmol of CM mg of TSS1 day1, the maximum specific growth rate (µmax) was 0.0506 day1, and the Monod half-saturation coefficient (Ks) was 0.067 (±0.004) µM. Under aerobic conditions, the values for k, µmax, and Ks were 10.7 (±0.11) µmol of CM mg of TSS1 day1, 0.145 day1, and 0.93 (±0.042) µM, respectively, indicating that NB1 used CM faster under aerobic conditions. Strain NB1 also grew on methanol, ethanol, and acetate under denitrifying and aerobic conditions, but not on methane, formate, or dichloromethane.
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