AME 80:223-242 (2017)  -  DOI:

Winter mixing impacts gene expression in marine microbial populations in the Gulf of Aqaba

D. Miller1, U. Pfreundt2,3, S. Hou2, S. C. Lott2, W. R. Hess2, I. Berman-Frank1,*

1Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel
2Genetics and Experimental Bioinformatics, Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany
3Present address: ETH Zürich, Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, Stefano-Franscini-Platz 5, 8093 Zürich, Switzerland
*Corresponding author:

ABSTRACT: In aquatic systems, changes in temperature and irradiance fundamentally characterize the water column and regulate microbial population structure and function. In systems with stable thermal stratification, the warm surface mixed layer is typically nutrient impoverished, limiting biological production. In periods of destratification, convective mixing of the water column exposes the microorganisms inhabiting these mixed systems to rapid variations in light availability and spectra. We explored the impact of winter deep-mixing (500 m deep mixed layer) on microbial communities from the surface (2.5 m) and the aphotic waters (440 m) in the Gulf of Aqaba by examining changes in both population composition and function via DNA and RNA sequencing. The greatest fraction of 16S sequences was assigned to Euryarchaeota, while metatranscriptomes were dominated by Synechococcus transcripts. Community composition was highly similar at both depths, yet transcription profiles differed. Phototrophic organisms found at the photic surface overexpressed genes related to catabolism and energy metabolism, while genes affiliated with biosynthesis were overexpressed at the aphotic depth. Similar transcriptional trends were observed in the non-photoautotrophs SAR11, Euryarchaeota, and Thaumarchaeota, with niche partitioning based on differential utilization of nitrogen and phosphorus occurring between the 2 archaeal groups. We did not detect upregulated expression of cyanobacterial genes indicative of mixotrophy or glycogen metabolism in the aphotic zone, suggesting they survive the aphotic period by utilizing photosynthates produced in the photic zone. Indications for a mixotrophic lifestyle were observed for prasinophytes, with genes related to phagocytosis overexpressed at the aphotic depth compared with the surface.

KEY WORDS: Deep mixing · Red Sea · Metatranscriptomics · Cyanobacteria · SAR11 · Archaea · Prasinophytes

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Cite this article as: Miller D, Pfreundt U, Hou S, Lott SC, Hess WR, Berman-Frank I (2017) Winter mixing impacts gene expression in marine microbial populations in the Gulf of Aqaba. Aquat Microb Ecol 80:223-242.

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