Proteomic Insight
into Functional Changes of Proteorhodopsin-Containing
Bacterial Species <i>Psychroflexus torquis</i> under Different
Illumination and Salinity Levels
- Publication date
- Publisher
Abstract
The extremely psychrophilic proteorhodopsin-containing
bacterial
species <i>Psychroflexus torquis</i> is considered to be
a model sea-ice microorganism, which has adapted to an epiphytic lifestyle.
So far, not much is known about proteorhodopsin-based phototrophy
and associated life strategies of sea ice bacteria, although it has
been previously shown that <i>P. torquis</i> can gain growth
advantage from light using a proteorhodopsin proton pump, the activity
of which is influenced by environmental salinity. The comprehensive
quantitative proteomic study performed here indicated that <i>P. torquis</i> responds to changing salinity and illumination
conditions. Proteins in the electron-transfer chain were down-regulated
at a suboptimal salinity level, TonB-dependent transporters increased
in abundance under supra-optimal salinity and decreased under suboptimal
salinity. In addition, several anaplerotic CO<sub>2</sub> fixation
proteins and three putative light sensing proteins that contain PAS
and GAF domains became more abundant under illumination. Furthermore,
central metabolic pathways (TCA and glycolysis) were also induced
by both salinity stress and illumination. The data suggest that <i>P. torquis</i> responded to changes in both light energy and
salinity to modulate membrane and central metabolic proteins that
are involved in energy production as well as nutrient uptake and gliding
motility processes that would be especially advantageous during the
polar summer ice algal bloom