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Applied and Environmental Microbiology, July 2002, p. 3467-3477, Vol. 68, No. 7
0099-2240/02/$04.00+0 DOI: 10.1128/AEM.68.7.3467-3477.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Laboratory of Microbial Ecology, Center for Ecological and Evolutionary Studies, University of Groningen, 9751 NN Haren, The Netherlands,1 Department of Industrial Microbiology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland,2 Department of Biological Sciences, University of Idaho, Moscow, Idaho 83844-30513
Received 15 October 2001/ Accepted 16 April 2002
To assess the extent of genotypic and phenotypic diversity within species of purple nonsulfur bacteria found in aquatic sediments, a total of 128 strains were directly isolated from agar plates that had been inoculated with sediment samples from Haren and De Biesbosch in The Netherlands. All isolates were initially characterized by BOX-PCR genomic DNA fingerprinting, and 60 distinct genotypes were identified. Analyses of 16S rRNA gene sequences of representatives of each genotype showed that five and eight different phylotypes of purple nonsulfur bacteria were obtained from the Haren and De Biesbosch sites, respectively. At the Haren site, 80.5% of the clones were Rhodopseudomonas palustris, whereas Rhodoferax fermentans and Rhodopseudomonas palustris were numerically dominant at the De Biesbosch site and constituted 45.9 and 34.4% of the isolates obtained, respectively. BOX-PCR genomic fingerprints showed that there was a high level of genotypic diversity within each of these species. The genomic fingerprints of Rhodopseudomonas palustris isolates were significantly different for isolates from the two sampling sites, suggesting that certain strains may be endemic to each sampling site. Not all Rhodopseudomonas palustris isolates could degrade benzoate, a feature that has previously been thought to be characteristic of the species. There were differences in the BOX-PCR genomic fingerprints and restriction fragment length polymorphisms of benzoate-coenzyme A ligase genes and form I and form II ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) genes between benzoate-degrading and non-benzoate-degrading genotypes. The ability to distinguish these two Rhodopseudomonas palustris groups based on multiple genetic differences may reflect an incipient speciation event resulting from adaptive evolution to local environmental conditions.
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