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Applied and Environmental Microbiology, November 1999, p. 5089-5099, Vol. 65, No. 11
Fossil Fuels and Environmental Geochemistry
Postgraduate Institute (NRG)1 and Centre
for Molecular Ecology,
Received 23 March 1999/Accepted 21 July 1999
The diversity and ecology of natural communities of the
uncultivated bacterium Achromatium oxaliferum were studied
by use of culture-independent approaches. 16S rRNA gene sequences were PCR amplified from DNA extracted from highly purified preparations of
cells that were morphologically identified as A. oxaliferum present in freshwater sediments from three locations in northern England (Rydal Water, Jenny Dam, Hell Kettles). Cloning and sequence analysis of the PCR-amplified 16S rRNA genes revealed that multiple related but divergent sequences were routinely obtained from the A. oxaliferum communities present in all the sediments
examined. Whole-cell in situ hybridization with combinations of
fluorescence-labelled oligonucleotide probes revealed that the
divergent sequences recovered from purified A. oxaliferum
cells corresponded to genetically distinct Achromatium
subpopulations. Analysis of the cell size distribution of the
genetically distinct subpopulations demonstrated that each was also
morphologically distinct. Furthermore, there was a high degree of
endemism in the Achromatium sequences recovered from
different sediments; identical sequences were never recovered from
different sampling locations. In addition to ecological differences that were apparent between Achromatium communities from
different freshwater sediments, the distribution of different
subpopulations of Achromatium in relation to sediment redox
profiles indicated that the genetically and morphologically distinct
organisms that coexisted in a single sediment were also ecologically
distinct and were adapted to different redox conditions. This result
suggests that Achromatium populations have undergone
adaptive radiation and that the divergent Achromatium
species occupy different niches in the sediments which they inhabit.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Natural Communities of Achromatium
oxaliferum Comprise Genetically, Morphologically, and Ecologically
Distinct Subpopulations
*
Corresponding author. Mailing address: Fossil Fuels and
Environmental Geochemistry Postgraduate Institute (NRG), University of
Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom. Phone: 44 (0)
191 222 7024. Fax: 44 (0) 191 222 5431. E-mail:
i.m.head{at}newcastle.ac.uk.
Applied and Environmental Microbiology, November 1999, p. 5089-5099, Vol. 65, No. 11
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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