Lineage: Bacteria[3914]; Firmicutes[795]; Clostridia[294]; Clostridiales[248]; Clostridiaceae[57]; Clostridium[49]; Clostridium acetobutylicum[1]Clostridium. This genus comprises about 150 metabolically diverse species of anaerobes that are ubiquitous in virtually all anoxic habitats where organic compounds are present, including soils, aquatic sediments and the intestinal tracts of animals and humans. Characteristic of clostridia is the shape of their cells that resembles a drumstick or spindle ("kloster" is Greek for "spindle"). This shape is attributed to the presence of endospores that develop under conditions unfavorable for vegetative growth and distend single cells terminally or sub-terminally. The endospores of many species are extremely sturdy and survive extended boiling in water and exposure to air. Spores germinate under conditions favorable for vegetative growth, such as anaerobiosis and presence of organic substrates. From the evolutionary perspective, clostridia are considered to be the most ancient bacteria. It is believed that present day Mollicutes (Eubacteria) have evolved regressively (i.e., by genome reduction) from gram-positive clostridia-like ancestors with a low GC content in DNA. Several species of clostridia (e.g., C. perfringens, C. botulinum, C. tetani) are known opportunistic toxin-producing pathogens in animals and humans. Some species are capable of producing organic solvents (acetone, ethanol, etc,), molecular hydrogen and other useful compounds. There are also species that can fix molecular nitrogen and thus are important participants in biological turnaround of nitrogen compounds in nature.Clostridium acetobutylicum. This organism is a benign saccharolytic and proteolytic soil bacterium capable of producing a number of organic solvents (solventogenic bacterium) through fermentation of various organic compounds. The first strains of C. acetobutyricum were isolated by Chaim Weizman during the World War I and used to develop industrial starch-based acetone, butanol and ethanol fermentation processes. [Source: NCBI Genome ]