Bacteria Genomes - SYMBIOBACTERIUM THERMOPHILUS

Symbiobacterium thermophilum is a Gram-negative and tryptophanase-positive thermophile, it is an uncultivable bacterium isolated from compost that depends on microbial commensalism. It does not grow by itself under standard culture conditions; however, when cocultured with Bacillus sp. strain S, it propagates up to 5 x 10 8 cells/ml. S.thermophilus proliferates under both aerobic and anaerobic conditions.

The 16S ribosomal DNA-based phylogeny suggests that this bacterium belongs to an unknown taxon in the Gram-positive bacterial cluster.

Studies have revealed unique features in the S.thermophilus genome. These features suggest that S.thermophilusis adaptable to and can live in various environments, such that its growth requirement could be a substance or a physiological condition that is generally available in the natural environment rather than a highly specific substance that is present only in a limited niche. The genomic information from S.thermophilus offers new insights into microbial diversity and evolutionary sciences, and provides a framework for characterising the molecular basis underlying microbial commensalism.

Also the S.thermophilus genome contains a set of genes involved in endospore formation, and that the organism is actually capable of forming endospores. Till date, the general understanding has been that the ability to form endospores is distributed only in the Bacilli and Clostridia, and hence the sporulation-related genes known thus far have a low GC content. On the other hand, the GC content of the S.thermophilus counterparts was as high as that of the entire genome, which provides the first genetic evidence of the presence of high GC endospore-forming bacterium

A comparative analysis indicated that the genome does not exhibit structural similarity to that of other prokaryotes known so far.

References:

Int. J. Syst. Evol. Microbiol. 50 1829-1832 (2000)
Nucleic Acids Research 32(16):4937-4944 2004