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Human activities in the Antarctic have resulted in hydrocarbon contamination of these fragile polar soils. Bioremediation is one of the options for remediation of these sites. However, little is known about anaerobic hydrocarbon degradation in polar soils and the influence of bioremediation practices on these processes. Using a field trial at Old Casey Station, Antarctica, we assessed the influence of fertilization on the anaerobic degradation of a 20-year old fuel spill. Fertilization increased hydrocarbon degradation in both anaerobic and aerobic soils when compared to controls, but was of most benefit for anaerobic soils where evaporation was negligible. This increased biodegradation in the anaerobic soils corresponded with a shift in the denitrifier community composition and an increased abundance of denitrifiers and benzoyl-CoA reductase. A microcosm study using toluene and hexadecane confirmed the degradative capacity within these soils under anaerobic conditions. It was observed that fertilized anaerobic soil degraded more of this hydrocarbon spike when incubated anaerobically than when incubated aerobically. We conclude that denitrifiers are actively involved in hydrocarbon degradation in Antarctic soils and that fertilization is an effective means of stimulating their activity. Further, when communities stimulated to degrade hydrocarbons under anaerobic conditions are exposed to oxygen, hydrocarbon degradation is suppressed. The commonly accepted belief that remediation of polar soils requires aeration needs to be reevaluated in light of this new data. [ABSTRACT FROM AUTHOR]

The extremely psychrophilic proteorhodopsin-containing bacterial species Psychroflexus torquis 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 P. torquis 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 P. torquis 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 CO2 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 P. torquis 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.