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

• Published in: Aquatic Microbial Ecology
• Main Authors: Lami, Raphaël, Kirchman, David L.
• Other Authors: Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), PIERRE FABRE-EDF (EDF)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), School of Marine Science and Policy, College of Earth, Ocean, and Environment Newark (CEOE), University of Delaware Newark -University of Delaware Newark
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Marine bacteria; SAR11; Proteorhodopsin; Quantitative PCR; [SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology; [SDV.BBM.GTP]Life Sciences [q-bio]/Biochemistry; Molecular Biology/Genomics [q-bio.GN]; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; North Atlantic
• Online Access: https://hal.sorbonne-universite.fr/hal-02906988; https://hal.sorbonne-universite.fr/hal-02906988/document; https://hal.sorbonne-universite.fr/hal-02906988/file/a073p185.pdf; https://doi.org/10.3354/ame01716

International audience 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 un- clear, especially in natural environments. We examined these relationships during 3 diurnal stud- ies 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.