Effect of temperature on sulphate reduction, growth rate and growth yield in five psychrophilic sulphate-reducing bacteria from Arctic sediments

Five psychrophilic sulphate-reducing bacteria (strains ASv26, LSv21, PSv29, LSv54 and LSv514) isolated from Arctic sediments were examined for their a daptation to permanently low temperatures, All strains grew at -1.8 degrees C, the freezing point of sea water, but their optimum temperature for grow th (T-opt) were 7 degrees C (PSv29), 10 degrees C (ASv26, LSv54) and 18 deg rees C (LSv21, LSv514), Although T-opt was considerably above the in situ t emperatures of their habitats (-1.7 degrees C and 2.6 degrees C), relative growth rates were still high at 0 degrees C, accounting for 25-41% of those at T-opt. Short-term incubations of exponentially growing cultures showed that the highest sulphate reduction rates occurred 2-9 degrees C above T-op t. In contrast to growth and sulphate reduction rates, growth yields of str ains ASv26, LSv54 and PSv29 were almost constant between -1.8 degrees C and T-opt. For strains LSv21 and LSv514, however, growth yields were highest a t the lowest temperatures, around 0 degrees C. The results indicate that ps ychrophilic sulphate-reducing bacteria are specially adapted to permanently low temperatures by high relative growth rates and high growth yields at i n site conditions.