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ISME J. 2011 Oct;5(10):1641-51. doi: 10.1038/ismej.2011.36. Epub 2011 Apr 7.

Light-induced transcriptional responses associated with proteorhodopsin-enhanced growth in a marine flavobacterium.

Author information

1
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Abstract

Proteorhodopsin (PR) is a photoprotein that functions as a light-driven proton pump in diverse marine Bacteria and Archaea. Recent studies have suggested that PR may enhance both growth rate and yield in some flavobacteria when grown under nutrient-limiting conditions in the light. The direct involvement of PR, and the metabolic details enabling light-stimulated growth, however, remain uncertain. Here, we surveyed transcriptional and growth responses of a PR-containing marine flavobacterium during carbon-limited growth in the light and the dark. As previously reported (Gómez-Consarnau et al., 2007), Dokdonia strain MED134 exhibited light-enhanced growth rates and cell yields under low carbon growth conditions. Inhibition of retinal biosynthesis abolished the light-stimulated growth response, supporting a direct role for retinal-bound PR in light-enhanced growth. Among protein-coding transcripts, both PR and retinal biosynthetic enzymes showed significant upregulation in the light. Other light-associated proteins, including bacterial cryptochrome and DNA photolyase, were also expressed at significantly higher levels in the light. Membrane transporters for Na(+)/phosphate and Na(+)/alanine symporters, and the Na(+)-translocating NADH-quinone oxidoreductase (NQR) linked electron transport chain, were also significantly upregulated in the light. Culture experiments using a specific inhibitor of Na(+)-translocating NQR indicated that sodium pumping via NQR is a critical metabolic process in the light-stimulated growth of MED134. In total, the results suggested the importance of both the PR-enabled, light-driven proton gradient, as well as the generation of a Na(+) ion gradient, as essential components for light-enhanced growth in these flavobacteria.

PMID:
21472017
PMCID:
PMC3176510
DOI:
10.1038/ismej.2011.36
[Indexed for MEDLINE]
Free PMC Article

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