Bacteria Genomes - THERMUS THERMOPHILUS

Thermus thermophilus is a Gram-negative , aerobic eubacterium which can grow at temperatures ranging from 50 to 82C.

The organism, strain HB27, was originally isolated from a natural thermal environment in Japan. Optimal growth occurs at 68C and pH 7.0. The strain exhibits a high competence for natural transformation and is therefore amenable to genetic manipulation.

Most extreme thermophiles that live in geothermal environments are strict anaerobes as a consequence of the adaptation to the low solubility of oxygen at these temperatures. However, Thermus species are an exception because they are strictly aerobic chemorganotrophs. For example Thermus thermophilus HB8 is able to grow anaerobically in the presence of nitrate due to synthesis of the nitrate reductase complex encoded by the nar operon. Expression from this operon is induced under low oxygen concentrations when nitrate is present. T. thermophilus HB27 however, was unable to grow under these anaerobic conditions. Researchers demonstrate that the ability to grow anaerobically by nitrate reduction can be transferred to the aerobic strain HB27 by conjugation. This conjugation event is dependent on the integration of a conjugative plasmid containing the nar operon into the HB8 chromosome which can then mobilise the chromosome in an Hfr-like (high frequency of recombination) mechanism which can also mobilize other chromosomal markers in a time-dependent way.

Besides the interest in basic research, e.g. the structural basis of protein thermostability or the adaptation strategies for survival at high temperatures, biotechnological applications of some thermostable enzymes contribute to the interest in T. thermophilus. This intrinsic stability and resistance to denaturing physical and chemical factors are considerable advantages in industrial processes. Some enzymes of Thermus species are already used in biotechnological applications such as DNA polymerase, an indispensable enzyme used in PCR techniques. Other fields of application for thermostable enzymes are starch-processing ( e.g. -amylases, glucose isomerases), organic synthesis ( e.g. esterases, lipases, proteases), diagnostics, waste treatment, pulp and paper manufacture ( e.g. xylanases), and animal feed and human food (amino acid and vitamin synthesis).

Researchers have begun to make comparisons between the mesophilic bacterium Deinococcus radiodurans and T. thermophilus. Both organisms share a similar set of proteins, although their genomes lack extensive synteny. Many new genes of potential interest for biotechnological applications were found in T. thermophilus HB27. Candidates include various proteases and key enzymes of other fundamental biological processes such as DNA replication, DNA repair and RNA maturation.

References:

http://www.g2l.bio.uni-goettingen.de/projects/c_proj_tt.html
http://www.tsukuba.ac.jp/eng/index.html
http://www.nature.com/
http://www.science.siu.edu/microbiology/micr460/460%20Pages/460.horizanaerob.html