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Applied and Environmental Microbiology, February 2009, p. 897-906, Vol. 75, No. 4
0099-2240/09/$08.00+0 doi:10.1128/AEM.01830-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Community-Level Analysis of psbA Gene Sequences and Irgarol Tolerance in Marine Periphyton
K. M. Eriksson,1*
A. K. Clarke,1
L.-G. Franzen,2
M. Kuylenstierna,3
K. Martinez,4 and
H. Blanck1
Department of Plant and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Göteborg, Sweden,1 Halmstad University, Box 823, SE-301 18 Halmstad, Sweden,2 Department of Marine Ecology, University of Gothenburg, Sven Lovén Centre for Marine Sciences Kristineberg, SE-450 34 Fiskebäckskil, Sweden,3 Spanish National Research Council—IIQAB-CSIC, Department of Ecotechnology, Josep Pascual Vila, Jordi Girona 18-26, 08034 Barcelona, Spain4
Received 7 August 2008/ Accepted 5 December 2008
This study analyzes psbA gene sequences, predicted D1 protein sequences, species relative abundance, and pollution-induced community tolerance in marine periphyton communities exposed to the antifouling compound Irgarol 1051. The mechanism of action of Irgarol is the inhibition of photosynthetic electron transport at photosystem II by binding to the D1 protein. The metagenome of the communities was used to produce clone libraries containing fragments of the psbA gene encoding the D1 protein. Community tolerance was quantified with a short-term test for the inhibition of photosynthesis. The communities were established in a continuous flow of natural seawater through microcosms with or without added Irgarol. The selection pressure from Irgarol resulted in an altered species composition and an inducted community tolerance to Irgarol. Moreover, there was a very high diversity in the psbA gene sequences in the periphyton, and the composition of psbA and D1 fragments within the communities was dramatically altered by increased Irgarol exposure. Even though tolerance to this type of compound in land plants often depends on a single amino acid substitution (Ser264
Gly) in the D1 protein, this was not the case for marine periphyton species. Instead, the tolerance mechanism likely involves increased degradation of D1. When we compared sequences from low and high Irgarol exposure, differences in nonconserved amino acids were found only in the so-called PEST region of D1, which is involved in regulating its degradation. Our results suggest that environmental contamination with Irgarol has led to selection for high-turnover D1 proteins in marine periphyton communities at the west coast of Sweden.
* Corresponding author. Mailing address: Sven Lovén Centre for Marine Sciences, Kristineberg 566, SE-450 34 Fiskebäckskil, Sweden. Phone: 46 523 18538. Fax: 46 523 18502. E-mail: martin.eriksson{at}dpes.gu.se
Published ahead of print on 16 December 2008.
Applied and Environmental Microbiology, February 2009, p. 897-906, Vol. 75, No. 4
0099-2240/09/$08.00+0 doi:10.1128/AEM.01830-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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