Psychrotolerant and microaerophilic bacteria in boreal groundwater

Abstract Growth temperature and microaerophily of 39 phylogenetically different isolates from boreal oxygen-deficient groundwater were studied. Based on growth temperatures, the isolates were mainly psychrotolerant bacteria as 35 grew at 2 degrees C and only three at 35 degrees C. Growth rates in the range of 4-35 degrees C fitted the Ratkowsky square root model well. Optimum temperatures of the groundwater isolates varied between 18 and 30 degrees C. In semisolid glucose and PYGV media, 59% and 28% of the isolates, respectively, preferred microaerophilic growth and 33% were catalase-negative. The microaerophilic isolates had the highest sensitivity to H(2)O(2) whereas sensitivity to the superoxide generator paraquat was similar among microaerophilic and aerobic isolates. The results show that the cold (6-8 degrees C) and oxygen-deficient groundwater harbors psychrotolerant and microaerophilic bacteria of different phylogenetic origins which are well adapted to their environment.