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Journal of Bacteriology, November 2008, p. 7453-7463, Vol. 190, No. 22
0021-9193/08/$08.00+0     doi:10.1128/JB.00909-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Kinetic Analysis of Growth Rate, ATP, and Pigmentation Suggests an Energy-Spilling Function for the Pigment Prodigiosin of Serratia marcescens{triangledown}

Pryce L. Haddix,1* Sarah Jones,1 Pratik Patel,1 Sarah Burnham,1 Kaori Knights,1 Joan N. Powell,2 and Amber LaForm1

Departments of Biology,1 Mathematics, Auburn University Montgomery, P.O. Box 244023, Montgomery, Alabama 36124-40232

Received 1 July 2008/ Accepted 8 September 2008

Serratia marcescens is a gram-negative environmental bacterium and opportunistic pathogen. S. marcescens expresses prodigiosin, a bright red and cell-associated pigment which has no known biological function for producing cells. We present here a kinetic model relating cell, ATP, and prodigiosin concentration changes for S. marcescens during cultivation in batch culture. Cells were grown in a variety of complex broth media at temperatures which either promoted or essentially prevented pigmentation. High growth rates were accompanied by large decreases in cellular prodigiosin concentration; low growth rates were associated with rapid pigmentation. Prodigiosin was induced most strongly during limited growth as the population transitioned to stationary phase, suggesting a negative effect of this pigment on biomass production. Mathematically, the combined rate of formation of biomass and bioenergy (as ATP) was shown to be equivalent to the rate of prodigiosin production. Studies with cyanide inhibition of both oxidative phosphorylation and pigment production indicated that rates of biomass and net ATP synthesis were actually higher in the presence of cyanide, further suggesting a negative regulatory role for prodigiosin in cell and energy production under aerobic growth conditions. Considered in the context of the literature, these results suggest that prodigiosin reduces ATP production by a process termed energy spilling. This process may protect the cell by limiting production of reactive oxygen compounds. Other possible functions for prodigiosin as a mediator of cell death at population stationary phase are discussed.

* Corresponding author. Mailing address: Department of Biology, Room 311B Goodwyn Hall, Auburn University Montgomery, P.O. Box 244023, Montgomery, AL 36124-4023. Phone: (334) 244-3333. Fax: (334) 244-3826. E-mail: phaddix{at}aum.edu

{triangledown} Published ahead of print on 19 September 2008.

Journal of Bacteriology, November 2008, p. 7453-7463, Vol. 190, No. 22
0021-9193/08/$08.00+0     doi:10.1128/JB.00909-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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