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Applied and Environmental Microbiology, September 2003, p. 5186-5191, Vol. 69, No. 9
0099-2240/03/$08.00+0 DOI: 10.1128/AEM.69.9.5186-5191.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Bastiaan Star,1 Louis A. Huisman,1 Jan C. Gottschal,1 and Larry J. Forney2*
Laboratory of Microbial Ecology, Center for Ecological and Evolutionary Studies, University of Groningen, 9751 NN Haren, The Netherlands,1 Department of Biological Sciences, University of Idaho, Moscow, Idaho 83844-30512
Received 22 January 2003/ Accepted 4 June 2003
The biogeography of the purple nonsulfur bacterium Rhodopseudomonas palustris on a local scale was investigated. Thirty clones of phototrophic bacteria were isolated from each of five unevenly spaced sampling locations in freshwater marsh sediments along a linear 10-m transect, and a total of 150 clones were characterized by BOX-PCR genomic DNA fingerprinting. Cluster analysis of 150 genomic fingerprints yielded 26 distinct genotypes, and 106 clones constituted four major genotypes that were repeatedly isolated. Representatives of these four major genotypes were tentatively identified as R. palustris based on phylogentic analyses of 16S rRNA gene sequences. The differences in the genomic fingerprint patterns among the four major genotypes were accompanied by differences in phenotypic characteristics. These phenotypic differences included differences in the kinetics of carbon source use, suggesting that there may be functional differences with possible ecological significance among these clonal linages. Morisita-Horn similarity coefficients (CMH), which were used to compare the numbers of common genotypes found at pairs of sampling locations, showed that there was substantial similarity between locations that were 1 cm apart (CMH,
0.95) but there was almost no similarity between locations that were
9 m apart (CMH,
0.25). These calculations showed there was a gradual decrease in similarity among the five locations as a function of distance and that clones of R. palustris were lognormally distributed along the linear 10-m transect. These data indicate that natural populations of R. palustris are assemblages of genetically distinct ecotypes and that the distribution of each ecotype is patchy.
Present address: Department of Microbiology, University of Iowa, Iowa City, IA 52242.
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