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Light stimulated growth of proteorhodopsin bearing sea-ice psychrophile Psychroflexus torquis is salinity-dependent

Light stimulated growth of proteorhodopsin bearing sea-ice psychrophile Psychroflexus torquis is salinity-dependent
Shi Feng

Authors

Shi Feng1, Shane M Powell1, Richard Wilson2 and John P Bowman1

  1. Food Safety Centre, School of Agriculture Science, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, Australia
  2. Central Science Laboratory, University of Tasmania, Hobart, Tasmania, Australia

Abstract

Proteorhodopsins (PRs) are commonly found in marine prokaryotes and allow microbes to use light as an energy source. In recent studies it was reported that PR stimulates growth and survival under nutrient-limited conditions. In this study we tested the effect of nutrient and salinity stress on the extremely psychrophilic sea-ice bacterial species Psychroflexus torquis, which possesses PR. We demonstrated for the first time that light stimulated growth occurs under conditions of salinity stress rather than nutrient limitation and that elevated salinity is related to increased growth yields, PR levels and associated proton pumping activity. PR abundance in P. torquis also is post-transcriptionally regulated by both light and salinity and thus could represent an adaptation to its sea-ice habitat. Our findings extend the existing paradigm that light provides an energy source for marine prokaryotes under stress conditions other than nutrient limitation.

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