Field and Programs

Isolation and cultivation of extremophiles
It is now well known that microbial life can prevail, even thrive in the harshest environments. The biochemistry, molecular biology and evolution of these ‘extremophilic’ prokaryotes have recently come under intense scrutiny because of their general scientific curiosity and their potential for industrial applications. A novel anaerobic thermophilic bacterium named CBS-1 has been successfully isolated from a hot spring of Changbai Mountains, China. The results of physiological, biochemical and phylogenetic analysis indicated that this strain is a new species belonging to Fervidobacterium genus.

Structure-function relationship and molecular evolution of thermophilic enzymes
In order to gain a deep insight into the basic catalysis and stability mechanism of thermophilic enzyme, specialized techniques such as random mutagenesis, site-directed mutagenesis and kinetic assay were explored on thermostable esterase, glutamate dehydrogenase, phospholipase A2 and inorganic pyrophosphatase. The substrate specificity and optimal pH of esterase from Aeropyrum pernix K1 were altered by error-prone PCR and hot-spot site saturation mutagenesis.
Crystal structures of thermophilic enzyme can further elucidate the stability mechanism from a molecular level and provide a substantial rudiment for the rational design for the enzymes. Cooperating with Tsinghua university, our group has successfully resolved the crystal structures of thermophilic esterase, inorganic pyrophosphatase and histone. A reduction in thermolabile residues, additional aromatic residues, and more intimate association between subunits all contribute to the larger thermophilicity of Pho-PPase. The thermophilic archaeal histone HPhA has a larger hydrophobic contact area, an increased number of hydrogen bonds and a reduced solvent-accessible area. The identification of structural features that make thermophilic proteins more adaptable to extreme temperature should prove helpful for future biotechnology applications.
Bioinformatics techniques, such as molecular structure modeling and molecular dynamics simulation, have been applied to illuminate the Structure-function relationship and molecular evolution of thermophilic enzymes. The possible structural and functional effects of the mutations of thermostable esterase on the substrate discrimination were discussed based on molecular dynamics simulation studies. How a single amino acid governs the substrate discrimination of the enzyme of the POP family was confirmed.

Biotechnology application
Genome shuffling provides a new tool for cell and metabolic engineering that requires no sequence information or sophisticated genetic tools. Through mutagenesis and genome shuffling, we have screened out improved lactobacillus which can increase the production of L-lactic acids for the industrial production of L-lactic acid.
A hyperthermophilic archaeal histone from Pyrococcus horikoshii OT3 is an efficient and unharmful DNA carrier in gene transfer for gene therapy. Herewith, we recently engaged with establishing an efficient transfection method by using physiological agents and physiological conditions which will not perturb or damage cells, and which can be used in vivo.