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Applied and Environmental Microbiology, March 2006, p. 2200-2205, Vol. 72, No. 3
0099-2240/06/$08.00+0 doi:10.1128/AEM.72.3.2200-2205.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Zeki Naal,2,
Charles Moore,1
Emerilis Casado-Rivera,2
Hector D. Abruña,2
John D. Helmann,1 and
James P. Shapleigh1*
Cornell University, Department of Microbiology, Wing Hall, Ithaca, New York 14853,1 Cornell University, Department of Chemistry and Chemical Biology, Ithaca, New York2
Received 15 August 2005/ Accepted 9 January 2006
A series of experiments was undertaken to learn more about the impact on other bacteria of nitric oxide (NO) produced during denitrification. The denitrifier Rhodobacter sphaeroides 2.4.3 was chosen as a denitrifier for these experiments. To learn more about NO production by this bacterium, NO levels during denitrification were measured by using differential mass spectrometry. This revealed that NO levels produced during nitrate respiration by this bacterium were in the low µM range. This concentration of NO is higher than that previously measured in denitrifiers, including Achromobacter cycloclastes and Paracoccus denitrificans. Therefore, both 2.4.3 and A. cycloclastes were used in this work to compare the effects of various NO levels on nondenitrifying bacteria. By use of bacterial overlays, it was found that the NO generated by A. cycloclastes and 2.4.3 cells during denitrification inhibited the growth of both Bacillus subtilis and R. sphaeroides 2.4.1 but that R. sphaeroides 2.4.3 caused larger zones of inhibition in the overlays than A. cycloclastes. Both R. sphaeroides 2.4.3 and A. cycloclastes induced the expression of the NO stress response gene hmp in B. subtilis. Taken together, these results indicate that there is variability in the NO concentrations produced by denitrifiers, but, irrespective of the NO levels produced, microbes in the surrounding environment were responsive to the NO produced during denitrification.
Present address: Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Disorders, National Institutes of Health, Bethesda, MD 20892.
Present address: College of Pharmaceutical Sciences USP Ribeirão Preto, São Paulo, Brazil.
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