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Mechanisms of dominance: coexistence of picocyanobacterial genotypes in a freshwater ecosystem

Postius, C. and Ernst, A. (1999) Mechanisms of dominance: coexistence of picocyanobacterial genotypes in a freshwater ecosystem. Archives of Microbiology, 172, 69-75. ISSN 0302-8933.

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Official URL: http://dx.doi.org/10.1007/s002030050742

Abstract

The autotrophic picoplankton of the pelagic zone of the mesotrophic Lake Constance is dominated by phycoerythrin-rich unicellular cyanobacteria phylogenetically related to the marine Synechococcus and Prochlorococcus cluster. In Lake Constance, the abundance of picocyanobacteria shows a recurrent pattern of seasonal variations. Evidence of diverse subpopulations was obtained by electron-microscopic examination of natural water samples and isolated strains that unveiled different surface structures of picocyanobacteria. Further evidence was obtained by DNA analysis of 26 clonal isolates representing 12 different genotypes. Variations in light and nutrient supply revealed distinct abilities of the genetically different strains to cope with these stress situations. Furthermore, cultured heterotrophic nanoflagellates exhibited differential feeding preferences for certain Synechococcus strains. The findings imply that growth and loss rates of the natural cyanobacterial community may be influenced by its genetic composition. Phylogenetic analyses of isolated strains indicated that the physiological diversification of pelagic Synechococcus spp. has occurred during a recent adaptive radiation. An example for genetic mechanisms underlying physiological diversification is indicated by mobile DNA elements found in a Synechocystis strain also isolated from the pelagic zone of Lake Constance. The observations suggest that dominance of Synechococcus spp. was achieved by evolutionary adaptation and coexistence of numerous genotypes generating a physiologically highly diversified population. [KEYWORDS: cyanobacteria; Synechococcus spp.; autotrophic picoplankton; stress factors; physiological diversity; grazing; phylogenetic analysis Sp strain bo-8402; lake-constance; autotrophic picoplankton; phycoerythrin-rich; genetic diversity; water ecosystems; synechococcus; cyanobacteria; bacteria; marine]

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:10777
Deposited On:25 Nov 2011 01:00
Last Modified:31 Mar 2014 10:05

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