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Applied and Environmental Microbiology, September 2005, p. 5404-5410, Vol. 71, No. 9
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.9.5404-5410.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Extracellular DNA in Single- and Multiple-Species Unsaturated Biofilms

R. E. Steinberger and P. A. Holden*

Donald Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106

Received 1 September 2004/ Accepted 29 March 2005

The extracellular polymeric substances (EPS) of bacterial biofilms form a hydrated barrier between cells and their external environment. Better characterization of EPS could be useful in understanding biofilm physiology. The EPS are chemically complex, changing with both bacterial strain and culture conditions. Previously, we reported that Pseudomonas aeruginosa unsaturated biofilm EPS contains large amounts of extracellular DNA (eDNA) (R. E. Steinberger, A. R. Allen, H. G. Hansma, and P. A. Holden, Microb. Ecol. 43:416-423, 2002). Here, we investigated the compositional similarity of eDNA to cellular DNA, the relative quantity of eDNA, and the terminal restriction fragment length polymorphism (TRFLP) community profile of eDNA in multiple-species biofilms. By randomly amplified polymorphic DNA analysis, cellular DNA and eDNA appear identical for P. aeruginosa biofilms. Significantly more eDNA was produced in P. aeruginosa and Pseudomonas putida biofilms than in Rhodococcus erythropolis or Variovorax paradoxus biofilms. While the amount of eDNA in dual-species biofilms was of the same order of magnitude as that of of single-species biofilms, the amounts were not predictable from single-strain measurements. By the Shannon diversity index and principle components analysis of TRFLP profiles generated from 16S rRNA genes, eDNA of four-species biofilms differed significantly from either cellular or total DNA of the same biofilm. However, total DNA- and cellular DNA-based TRFLP analyses of this biofilm community yielded identical results. We conclude that extracellular DNA production in unsaturated biofilms is species dependent and that the phylogenetic information contained in this DNA pool is quantifiable and distinct from either total or cellular DNA.

* Corresponding author. Mailing address: Bren Hall, UCSB, Santa Barbara, CA 93106-5131. Phone: (805) 893-3195. Fax: (805) 893-7612. E-mail: holden{at}bren.ucsb.edu.

Applied and Environmental Microbiology, September 2005, p. 5404-5410, Vol. 71, No. 9
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.9.5404-5410.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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