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Applied and Environmental Microbiology, October 2005, p. 5850-5857, Vol. 71, No. 10
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.10.5850-5857.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Photoheterotrophic Metabolism of Acrylamide by a Newly Isolated Strain of Rhodopseudomonas palustris

David A. Wampler and Scott A. Ensign*

Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300

Received 14 February 2005/ Accepted 26 April 2005

Acrylamide, a neurotoxin and suspected carcinogen, is produced by industrial processes and during the heating of foods. In this study, the microbial diversity of acrylamide metabolism has been expanded through the isolation and characterization of a new strain of Rhodopseudomonas palustris capable of growth with acrylamide under photoheterotrophic conditions. The newly isolated strain grew rapidly with acrylamide under photoheterotrophic conditions (doubling time of 10 to 12 h) but poorly under anaerobic dark or aerobic conditions. Acrylamide was rapidly deamidated to acrylate by strain Ac1, and the subsequent degradation of acrylate was the rate-limiting reaction in cell growth. Acrylamide metabolism by succinate-grown cultures occurred only after a lag period, and the induction of acrylamide-degrading activity was prevented by the presence of protein or RNA synthesis inhibitors. 13C nuclear magnetic resonance studies of [1,2,3-13C]acrylamide metabolism by actively growing cultures confirmed the rapid conversion of acrylamide to acrylate but failed to detect any subsequent intermediates of acrylate degradation. Using concentrated cell suspensions containing natural abundance succinate as an additional carbon source, [13C]acrylate consumption occurred with the production and then degradation of [13C]propionate. Although R. palustris strain Ac1 grew well and with comparable doubling times for each of acrylamide, acrylate, and propionate, R. palustris strain CGA009 was incapable of significant acrylamide- or acrylate-dependent growth over the same time course, but grew comparably with propionate. These results provide the first demonstration of anaerobic photoheterotrophic bacterial acrylamide catabolism and provide evidence for a new pathway for acrylate catabolism involving propionate as an intermediate.

* Corresponding author. Mailing address: Department of Chemistry and Biochemistry, Utah State University, 0300 Old Main Hill, Logan, UT 84322. Phone: (435) 797-3969. Fax: (435) 797-3390. E-mail: ensigns{at}cc.usu.edu.

Applied and Environmental Microbiology, October 2005, p. 5850-5857, Vol. 71, No. 10
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.10.5850-5857.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.





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