Seasonal and spatial community dynamics in the meromictic Lake Cadagno
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O R I G I N A L PA P E R
Philipp P. Bosshard · Rolf Stettler · Reinhard Bachofen
Seasonal and spatial community dynamics in the meromictic Lake Cadagno
Received: 21 October 1999 / Revised: 20 June 2000 / Accepted: 20 June 2000 / Published online: 2 August 2000 © Springer-Verlag 2000
Abstract The seasonal and spatial variations in the community structure of bacterioplankton in the meromictic alpine Lake Cadagno were examined by temporal temperature gradient gel electrophoresis (TTGE) of PCR-amplified 16S rDNA fragments. Two different amplifications were performed, one specific for the domain Bacteria (Escherichia coli positions 8–536) and another specific for the family Chromatiaceae (E. coli positions 8–1005). The latter was followed by semi-nested reamplification with the bacterial primer set, allowing comparison of the two PCR approaches by TTGE. The TTGE patterns of samples from the chemocline and the anoxic monimolimnion were essentially identical, whereas the oxic mixolimnion displayed distinctively different banding patterns. For samples from the chemocline and the monimolimnion, dominant bands in the Bacteria-specific TTGE profiles comigrated with bands obtained by the semi-nested PCR approach specific for Chromatiaceae. This observation suggested that Chromatiaceae are in high abundance in the anoxic water layer. All dominant bands were excised and sequenced. Changes in the community structure, as indicated by changes in the TTGE profiles, were observed in samples taken at different times of the year. In the chemocline, Chromatium okenii was dominant in the summer months, whereas Amoebobacter purpureus populations dominated in autumn and winter. This change was confirmed by fluorescent in situ hybridization. Key words 16S rDNA · Temporal temperature gradient gel electrophoresis · Fluorescent in situ hybridization · Population dynamics · Meromixis · Bacterioplankton · Chemocline · Bacterial diversity · Chromatiaceae · Purple sulfur bacteria
P. P. Bosshard (✉) · R. Stettler · R. Bachofen Institute of Plant Biology, Department of Microbiology, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland e-mail: [email protected], Tel.: +41-1-6348286, Fax: +41-1-6348204
Abbreviations TTGE Temporal temperature gradient gel electrophoresis · DGGE Denaturing gradient gel electrophoresis · FISH Fluorescent in situ hybridization
Introduction The introduction of molecular biological techniques in microbial ecology has fundamentally changed our view of microbial diversity. It is nowadays accepted that only a minor part of the naturally occurring microbial species has been cultivated so far. Through the use of molecular techniques, many new phylotypes and new phylogenetic divisions have been described (Hugenholtz et al. 1998). Although the microbial diversity of various ecosystems has been investigated, relatively little is known about the temporal population dynamics of the species inhabiting these ecosystems. Recently developed techniques such as denaturing gradient gel electrophoresis (DGGE) and flu
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