AME 73:185-194 (2014)  -  DOI: https://doi.org/10.3354/ame01716

Diurnal expression of SAR11 proteorhodopsin and 16S rRNA genes in coastal North Atlantic waters

Raphaël Lami1,2,3,*, David L. Kirchman1

1University of Delaware, School of Marine Science and Policy, Lewes, Delaware 19958, USA
2Sorbonne Universités, UPMC Univ Paris 06, USR 3579, LBBM, Observatoire Océanologique, 66650 Banyuls-sur-Mer, France
3CNRS, USR 3579, LBBM, Observatoire Océanologique, 66650 Banyuls-sur-Mer, France
*Corresponding author:

ABSTRACT: Proteorhodopsins (PR) are phylogenetically widespread and highly expressed proton pumps in marine bacterial communities, including in the SAR11 clade, one of the most common clades in the oceans. The relationships between PR expression, light and cell activity remain unclear, especially in natural environments. We examined these relationships during 3 diurnal studies in spring, summer and fall in Delaware coastal waters. The abundance of genes and transcripts of SAR11 PR, SAR11 16S rRNA and total bacterial 16S rRNA were monitored using a quantitative PCR approach. We found that the expression of SAR11 PR was 2.5-fold higher during the day than at night. However, SAR11 16S rRNA levels remained constant during the day and night on all cruises, suggesting that the growth-related activity of SAR11 was not directly affected by sunlight. There was a tight correlation between expression of PR in SAR11 and photosynthetically active radiation, but not with other environmental parameters. Our data support the hypothesis that light affects PR expression by SAR11 populations, but the energy from PR appears to contribute relatively little to supporting bacterial growth-related activity in marine waters.


KEY WORDS: Marine bacteria · SAR11 · Proteorhodopsin · Quantitative PCR


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Cite this article as: Lami R, Kirchman DL (2014) Diurnal expression of SAR11 proteorhodopsin and 16S rRNA genes in coastal North Atlantic waters. Aquat Microb Ecol 73:185-194. https://doi.org/10.3354/ame01716

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