Proteorhodopsin in the ubiquitous marine bacterium SAR11.
ABSTRACT Proteorhodopsins are light-dependent proton pumps that are predicted to have an important role in the ecology of the oceans by supplying energy for microbial metabolism. Proteorhodopsin genes were first discovered through the cloning and sequencing of large genomic DNA fragments from seawater. They were later shown to be widely distributed, phylogenetically diverse, and active in the oceans. Proteorhodopsin genes have not been found in cultured bacteria, and on the basis of environmental sequence data, it has not yet been possible to reconstruct the genomes of uncultured bacterial strains that have proteorhodopsin genes. Although the metabolic effect of proteorhodopsins is uncertain, they are thought to function in cells for which the primary mode of metabolism is the heterotrophic assimilation of dissolved organic carbon. Here we report that SAR11 strain HTCC1062 ('Pelagibacter ubique'), the first cultivated member of the extraordinarily abundant SAR11 clade, expresses a proteorhodopsin gene when cultured in autoclaved seawater and in its natural environment, the ocean. The Pelagibacter proteorhodopsin functions as a light-dependent proton pump. The gene is expressed by cells grown in either diurnal light or in darkness, and there is no difference between the growth rates or cell yields of cultures grown in light or darkness.
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ABSTRACT: Bacteria that utilize sunlight to supplement metabolic activity are now being described in a range of ecosystems. While it is likely that phototrophy provides an important competitive advantage, the contribution that these microorganisms make to the bioenergetics of polar marine ecosystems is unknown. In this minireview, we discuss recent advances in our understanding of phototrophic bacteria and highlight the need for future research.Biology 01/2012; 1(3):542-56.
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ABSTRACT: A pure culture of an Actinobacterium previously described as Candidatus Rhodoluna lacicola strain MWH-Ta8 was established and deposited in two public culture collections. Strain MWH-Ta8T represents a free-living planktonic freshwater bacterium obtained from hypertrophic Meiliang Bay, Lake Taihu (Peoples Republic of China). The strain was characterized by phylogenetic and taxonomic investigations, as well as by determination of its complete genome sequence. Strain MWH-Ta8T is noticeable due to its unusually low values of cell size (0.05 μ(3)), genome size (1.43 Mbp), and G + C content of DNA (51.5 mol%). Phylogenetic analyses based on 16S rRNA and rpoB gene sequences suggested that strain MWH-Ta8T is affiliated with the family Microbacteriaceae with Pontimonas salivibrio being its closest related relative among the currently described species within this family. Strain MWH-Ta8T and the type strain of P. salivibrio shared a 16S rRNA sequence similarity of 94.3%. The cell-wall peptidoglycan of strain MWH-Ta8T was of type B2β (B10), containing 2,4-diaminobutyric acid as the diamino acid. The predominant cellular fatty acids were anteiso-C15:0 (36.5%), iso-C16:0 (16.5%), anteiso-C15:0 (15.6%) and iso-C14:0 (8.9%), and the major (> 10%) menaquinones were MK-11 and MK-12. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and two unknown glycolipids. The combined phylogenetic, phenotypic and chemotaxonomic data clearly suggest that strain MWH-Ta8T represents a novel genus and species in the family Microbacteriaceae, for which the name Rhodoluna lacicola gen. nov., sp. nov. is proposed. The type strain of Rhodoluna lacicola is MWH-Ta8T (=DSM 23834T, =LMG 26932T).International Journal of Systematic and Evolutionary Microbiology 07/2014; · 2.80 Impact Factor
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ABSTRACT: Marine metatranscriptome data was generated as part of a study investigating the bacterioplankton communities towards the end of a diatom-dominated spring phytoplankton bloom. This genomic resource article reports a metatranscriptomic dataset from amidst the winter time prior to the occurrence of the spring diatom bloom. Up to 58% of all sequences could be assigned to predicted genes. Taxonomic analysis based on expressed 16S ribosomal RNA genes identified Alphaproteobacteria and Gammaproteobacteria as the most active community members.Marine Genomics 11/2014; · 1.97 Impact Factor