Bacteria Genomes - THIOBACILLUS DENITRIFICANS

Thiobacillus are colourless, rod-shaped, Gram-negative strictly aerobic respiratory bacteria with polar flagella. They are obligate autotrophic organisms, meaning they require organic carbon both as an electron and carbon source. They obtain nutrients by oxidizing iron and sulfur. Thiobacillus do not form spores. Their life cycle is typical of bacteria, with reproduction by division.

Thiobacillus denitrificans is a widely distributed chemolithoautotrophic bacterium T. denitrificans is best known for its ability to couple the oxidation of inorganic sulfur compounds (such as hydrogen sulfide and thiosulfate) to denitrification, although it was recently found to couple the anaerobic oxidation of Fe(II) to denitrification as well. Among the inorganic electron donors that T. denitrificans can utilise are poorly-soluble minerals containing reduced iron and/or sulfur, such as pyrite (FeS2) and FeS.

T. denitrificans differs from many known chemolithotrophic sulfur-oxidizing bacteria (such as Acidithiobacillus ferrooxidans) in that it is a facultative anaerobe (it can respire aerobically or via denitrification) rather than an obligate aerobe and lives at circumneutral rather than acidic pH.

From an environmental perspective, T. denitrificans is a natural agent for intrinsic bioremediation of a major groundwater contaminant (nitrate). Many recent studies have shown that chemolithoautotrophic denitrification with pyrite or other reduced sulfur minerals as electron donors can be an important means of natural remediation of nitrate-contaminated groundwater. Nitrate contamination of groundwater is a pervasive and high-priority concern in rural and urban areas throughout the industrialised world. In addition to its remediation role in natural nitrate-contaminated environments, T. denitrificans has been used in engineered water treatment systems for nitrate removal.

Thiobacillus denitrificans, first isolated by Beijerinck over a century ago was one of the first nonfilamentous bacteria ever described to be capable of growth on inorganic sulfur compounds as sole energy sources. Strain ATCC 25259 was obtained from the American Type Culture Collection (ATCC). This strain was originally isolated in the 1960s and was deposited with the ATCC in 1969. The complete genome sequence of ATCC 25259 is the first to become available for an obligately chemolithoautotrophic, sulfur-compound-oxidizing, beta-proteobacterium.

T. denitrificans is the best studied of the very few obligate chemolithoautotrophic species known to couple denitrification tosulfur-compound oxidation ( Thiomicrospira denitrificans and Thioalkalivibrio thiocyanodenitrificans also have this ability).

References:

http://genome.jgi-psf.org/finished_microbes/thide/thide.home.html
http://rice.tigr.org/tigr-scripts/CMR2/GenomePage3.spl?database=nttd01