Introduction to the Physiology and Biochemistry of the Genus Clostridium

The genus Clostridium was created by Prazmowski in 1880. Four criteria presently classify an organism as a Clostridium: (1) the ability to form endospores; (2) restriction to an anaerobic energy metabolism; (3) the inability to carry out a dissimilatory reduction of sulfate; and (4) the possession of a gram-positive cell wall, which may react gram-negative. These criteria are met by an otherwise diverse assembly of microorganisms, and the genus Clostridium has grown to be one of the largest genera among prokaryotes. A total of 83 species are listed in Bergey’s Manual of Systematic Bacteriology (Cato et al., 1986). Since this list was compiled, a number of new species have been described, while others, such as C. tetanomorphum and C. cylindrosporum, have been omitted (see Chapter 1). In this chapter the span of properties found among the Clostridia will be outlined. Additional information on the general taxonomy, the general properties of Clostridia, and clostridial fermentations may be found in a number of recent reviews (Barker, 1961, 1978, 1981; Wood, 1961; Thauer et al., 1977; Gottschalk and Andreesen, 1979; Gottschalk et al., 1981; Booth and Mitchell, 1987).