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Applied and Environmental Microbiology, March 2001, p. 1375-1379, Vol. 67, No. 3
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.3.1375-1379.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Factors Affecting Catalase Expression in Pseudomonas aeruginosa Biofilms and Planktonic Cells

Jesse R. Frederick,1 James G. Elkins,1 Nikki Bollinger,1 Daniel J. Hassett,2 and Timothy R. McDermott1,3,*

Center for Biofilm Engineering1 and Department of Land Resources and Environmental Sciences,3 Montana State University, Bozeman, Montana 59717, and Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-05242

Received 29 August 2000/Accepted 14 December 2000

Previous work with Pseudomonas aeruginosa showed that catalase activity in biofilms was significantly reduced relative to that in planktonic cells. To better understand biofilm physiology, we examined possible explanations for the differential expression of catalase in cells cultured in these two different conditions. For maximal catalase activity, biofilm cells required significantly more iron (25 µM as FeCl3) in the medium, whereas planktonic cultures required no addition of iron. However, iron-stimulated catalase activity in biofilms was still only about one-third that in planktonic cells. Oxygen effects on catalase activity were also investigated. Nitrate-respiring planktonic cultures produced approximately twice as much catalase activity as aerobic cultures grown in the presence of nitrate; the nitrate stimulation effect could also be demonstrated in biofilms. Cultures fermenting arginine had reduced catalase levels; however, catalase repression was also observed in aerobic cultures grown in the presence of arginine. It was concluded that iron availability, but not oxygen availability, is a major factor affecting catalase expression in biofilms.

* Corresponding author. Mailing address: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717. Phone: (406) 994-2190. Fax: (406) 994-3933. E-mail: timmcder{at}montana.edu.

Applied and Environmental Microbiology, March 2001, p. 1375-1379, Vol. 67, No. 3
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.3.1375-1379.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.