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Seasonal bloom dynamics and ecophysiology of the freshwater sister clade of SAR11 bacteria 'that rule the waves' (LD12)


Salcher, M M; Pernthaler, J; Posch, T (2011). Seasonal bloom dynamics and ecophysiology of the freshwater sister clade of SAR11 bacteria 'that rule the waves' (LD12). ISME Journal, 5(8):1242-1252.

Abstract

Alphaproteobacteria are common members of marine bacterioplankton assemblages, but are believed to be rare in lacustrine systems. However, uncultured Alphaproteobacteria of the freshwater LD12 lineage form a tight monophyletic sister group with the numerically dominant bacteria in marine epipelagic waters, the SAR11 clade or genus Pelagibacter. Comparative rRNA sequence analysis reveals a global occurrence of LD12 bacteria in freshwater systems. The association of genotypic subclades with single-study systems moreover suggests a regional diversification. LD12 bacteria exhibit distinct and annually recurring spatio-temporal distribution patterns in prealpine lakes, as assessed by seasonally resolved vertical profiling and high-throughput cell counting. During the summer months, these ultramicrobacteria can form cell densities in the surface (epilimnetic) water layers that are comparable to those of their marine counterparts (>5 x 10(8) cells per l). LD12 bacteria had a pronounced preference for glutamine and glutamate over 7 other amino acids in situ, and they exhibited substantially higher uptake of these two substrates (and glycine) than the microbial assemblage in general. In addition, members of LD12 were also able to exploit other monomeric sources of organic carbon such as glucose, fructose or acetate. LD12 seemed to follow an oligotrophic lifestyle with slow but efficient uptake already at low substrate concentrations. Thus, LD12 bacteria do not only share phenotypic and metabolic traits with Pelagibacter, but also seem to thrive in the analogous spatiotemporal niche in freshwaters. The two groups together form one of the rare monophyletic lineages of ultramicrobacteria that have successfully traversed the barrier between marine and freshwater habitats. The ISME Journal (2011) 5, 1242-1252; doi:10.1038/ismej.2011.8; published online 17 March 2011

Alphaproteobacteria are common members of marine bacterioplankton assemblages, but are believed to be rare in lacustrine systems. However, uncultured Alphaproteobacteria of the freshwater LD12 lineage form a tight monophyletic sister group with the numerically dominant bacteria in marine epipelagic waters, the SAR11 clade or genus Pelagibacter. Comparative rRNA sequence analysis reveals a global occurrence of LD12 bacteria in freshwater systems. The association of genotypic subclades with single-study systems moreover suggests a regional diversification. LD12 bacteria exhibit distinct and annually recurring spatio-temporal distribution patterns in prealpine lakes, as assessed by seasonally resolved vertical profiling and high-throughput cell counting. During the summer months, these ultramicrobacteria can form cell densities in the surface (epilimnetic) water layers that are comparable to those of their marine counterparts (>5 x 10(8) cells per l). LD12 bacteria had a pronounced preference for glutamine and glutamate over 7 other amino acids in situ, and they exhibited substantially higher uptake of these two substrates (and glycine) than the microbial assemblage in general. In addition, members of LD12 were also able to exploit other monomeric sources of organic carbon such as glucose, fructose or acetate. LD12 seemed to follow an oligotrophic lifestyle with slow but efficient uptake already at low substrate concentrations. Thus, LD12 bacteria do not only share phenotypic and metabolic traits with Pelagibacter, but also seem to thrive in the analogous spatiotemporal niche in freshwaters. The two groups together form one of the rare monophyletic lineages of ultramicrobacteria that have successfully traversed the barrier between marine and freshwater habitats. The ISME Journal (2011) 5, 1242-1252; doi:10.1038/ismej.2011.8; published online 17 March 2011

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Plant and Microbial Biology
Dewey Decimal Classification:580 Plants (Botany)
Language:English
Date:1 August 2011
Deposited On:05 Mar 2012 16:07
Last Modified:05 Apr 2016 15:40
Publisher:Nature Publishing Group
ISSN:1751-7362
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:10.1038/ismej.2011.8
PubMed ID:21412347
Permanent URL: http://doi.org/10.5167/uzh-59995

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