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Applied and Environmental Microbiology, July 2009, p. 4391-4397, Vol. 75, No. 13
0099-2240/09/$08.00+0     doi:10.1128/AEM.01567-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

CO2 Production as an Indicator of Biofilm Metabolism{triangledown} ,{dagger}

Otini Kroukamp and Gideon M. Wolfaardt*

Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada

Received 9 July 2008/ Accepted 30 March 2009

Biofilms are important in aquatic nutrient cycling and microbial proliferation. In these structures, nutrients like carbon are channeled into the production of extracellular polymeric substances or cell division; both are vital for microbial survival and propagation. The aim of this study was to assess carbon channeling into cellular or noncellular fractions in biofilms. Growing in tubular reactors, biofilms of our model strain Pseudomonas sp. strain CT07 produced cells to the planktonic phase from the early stages of biofilm development, reaching pseudo steady state with a consistent yield of ~107 cells·cm–2·h–1 within 72 h. Total direct counts and image analysis showed that most of the converted carbon occurred in the noncellular fraction, with the released and sessile cells accounting for <10% and <2% of inflowing carbon, respectively. A CO2 evolution measurement system (CEMS) that monitored CO2 in the gas phase was developed to perform a complete carbon balance across the biofilm. The measurement system was able to determine whole-biofilm CO2 production rates in real time and showed that gaseous CO2 production accounted for 25% of inflowing carbon. In addition, the CEMS made it possible to measure biofilm response to changing environmental conditions; changes in temperature or inflowing carbon concentration were followed by a rapid response in biofilm metabolism and the establishment of new steady-state conditions.

* Corresponding author. Mailing address: Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada. Phone: (416) 979-5000, ext. 4051. Fax: (416) 979-5044. E-mail: gwolfaar{at}ryerson.ca

{triangledown} Published ahead of print on 3 April 2009.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, July 2009, p. 4391-4397, Vol. 75, No. 13
0099-2240/09/$08.00+0     doi:10.1128/AEM.01567-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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