Isolation and characterization of psychrotrophs from subterranean environments

Subterranean environments are potential sources for the isolation of novel microorganisms. Water and soil samples were collected at depths ranging fro m 10 to 1800 meters below the surface, and screening was carried out with a erobic rich and anaerobic minimal media. Two psychrotrophic anal three chem oautotrophic strains were isolated. One of the psychrotrophic isolates, des ignated SN16A, grew at temperatures between -5 and 37 degrees C with optima l growth between 25 and 30 degrees C. The other psychrotroph, designated KB 700A, grew between -10 and 30 degrees C. Little difference in growth rate c ould be observed between 20 and 30 degrees C; however, this strain did not grow at 37 degrees C. KB700A utilized CO2 chemoautotrophically at 30 degree s C, using hydrogen as an energy source. Both strains were characterized bi ochemically. The complete 16S rRNA sequence of KB700A was 98.7% homologous with that of Pseudomonas marginalis. However, the 16S rRNA of SN16A showed only 95.4% identity at maximum-with the corresponding gene of Arthrobacter globiformis-suggesting that this strain may belong to a novel genus. Both s trains exhibited the ability to produce hydrolytic enzymes on plate assays. Our results suggest that subterranean environments are promising sources f or the isolation of psychrotrophic microorganisms.