Isolation and characterization of a novel organic solvent-tolerant Anoxybacillus sp. PGDY12, a thermophilic Gram-positive bacterium

Aims: To isolate and characterize new bacteria capable of tolerating high concentrations of organic solvents at high temperature. Methods and Results: A solvent-tolerant, thermophilic bacterium was isolated from hot spring samples at 55 degrees C. The strain PGDY12 was characterized as a Gram-positive bacterium. It was able to tolerate 100% solvents, such as toluene, benzene and p-xylene on plate overlay and high concentrations of these solvents in liquid cultures. A comparison of growth showed that 0.2% (v/v) benzene and 0.15% (v/v) p-xylene were capable of enhancing the final cell yields. Transmission electron micrographs showed the incrassation of electron-transparent intracellular material and the distorted cytoplasm in case of the cells grown in toluene. A phylogenetic analysis based on 16S rRNA sequence data indicated that the strain PGDY12 was member of the genus Anoxybacillus. Conclusions: The thermophilic, Gram-positive Anoxybacillus sp. PGDY12 exhibited a unique and remarkable ability to tolerate solvents at 55 degrees C. Significance and Impact of the Study: The solvent tolerance properties are less known in thermophilic bacteria. The Anoxybacillus sp. PGDY12 is the first strictly thermophilic bacterium able to tolerate a broad range of solvents. This strain is a promising candidate for use as a high temperature biocatalyst in the biotechnological applications.