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Applied and Environmental Microbiology, February 2000, p. 499-508, Vol. 66, No. 2
Departament de Biologia Marina i
Oceanografia, Institut de Ciències del Mar-CSIC, E-08039
Barcelona,1 and Institut d'Ecologia
Aquàtica, Universitat de Girona, E-17071
Girona,3 Spain, and
Max-Planck-Institute for Marine Microbiology, D-28359
Bremen, Germany2
Received 6 July 1999/Accepted 4 November 1999
The microbial assemblages of Lake Cisó and Lake Vilar
(Banyoles, northeast Spain) were analyzed in space and time by
microscopy and by performing PCR-denaturing gradient gel
electrophoresis (DGGE) and sequence analysis of 16S rRNA gene
fragments. Samples obtained from different water depths and at two
different times of the year (in the winter during holomixis and in the
early spring during a phytoplankton bloom) were analyzed. Although the
lakes have the same climatic conditions and the same water source, the limnological parameters were different, as were most of the
morphologically distinguishable photosynthetic bacteria enumerated by
microscopy. The phylogenetic affiliations of the predominant DGGE bands
were inferred by performing a comparative 16S rRNA sequence analysis. Sequences obtained from Lake Cisó samples were related to
gram-positive bacteria and to members of the division
Proteobacteria. Sequences obtained from Lake Vilar samples
were related to members of the Cytophaga-Flavobacterium-Bacteroides phylum and to
cyanobacteria. Thus, we found that like the previously reported
differences between morphologically distinct inhabitants of the two
lakes, there were also differences among the community members whose
morphologies did not differ conspicuously. The changes in the species
composition from winter to spring were also marked. The two lakes both
contained sequences belonging to phototrophic green sulfur bacteria,
which is consistent with microscopic observations, but these sequences were different from the sequences of cultured strains previously isolated from the lakes. Euryarchaeal sequences (i.e., methanogen- and
thermoplasma-related sequences) also were present in both lakes. These
euryarchaeal group sequences dominated the archaeal sequences in Lake
Cisó but not in Lake Vilar. In Lake Vilar, a new planktonic
population related to the crenarchaeota produced the dominant archaeal
band. The phylogenetic analysis indicated that new bacterial and
archaeal lineages were present and that the microbial diversity of
these assemblages was greater than previously known. We evaluated the
correspondence between the abundances of several morphotypes and DGGE
bands by comparing microscopy and sequencing results. Our data provide
evidence that the sequences obtained from the DGGE fingerprints
correspond to the microorganisms that are actually present at higher
concentrations in the natural system.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Identification of and Spatio-Temporal Differences
between Microbial Assemblages from Two Neighboring Sulfurous Lakes:
Comparison by Microscopy and Denaturing Gradient Gel
Electrophoresis

*
Corresponding author. Mailing address: Departament de
Biologia Marina i Oceanografia, Institut de Ciències del
Mar-CSIC, P. Joan de Borbó s/n, E-08039 Barcelona, Spain. Phone:
34-932216416. Fax: 34-932217340. E-mail:
casamayor{at}icm.csic.es.
Present address: Netherlands Institute of Sea Research, NL-1790 AB
Den Burg, The Netherlands.
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