Clostridial Origin

Another study (Self and Stadtman 2000) described the purification of XDH from C. purinolyticum, a purine-fermenting strain originally isolated as an adenine-fermentor (Dtirre et al. 1981). Selenium was labile (cyanolyzable) and required for XDH activity. Similar to XDH from E. barkeri, XDH from C. purinolyticum consisted of three subunits (determined by SDS-PAGE). However, XDH from C. purinolyticum was significantly stable when isolated under aerobic conditions. Although these reports solidify the previously speculative data that selenium is present as a labile cofactor in clostridial XDH, the exact nature of selenium and the molecules to which... 

Bayer et al. (7) succeeded in reconstituting clostridial ferredoxin from a, a -dipyridyl-treated apoferredoxin in the presence of ferrous ion without the presence of a labile sulfur source. Based on this observation, they proposed that labile sulfur originates from cysteinyl residues in the presence of iron. Contrary to their finding, Rabinowitz and his coworkers (21, 33) demonstrated that the reconstitution of clostridial ferredoxin from mersaryl-, a, a -dipyridyl-, and trichloroacetic acid-treated apo-ferredoxins absolutely requires the addition of hydrogen sulfide. Consequently, they concluded that cysteine is not the source of labile sulfur . 

It is interesting to note that the UV spectrum for the ferredoxin from chromatium, a photosynthesizing bacteria, suggests that it is very similar, if not identical, to that of the ferredoxin from clostridia, which are nonphotosynthetic organisms. It was originally suggested that this is a form of ferredoxin intermediate between the plant type and the clostridial type, because chemical analysis suggested that the iron content was intermediate between the chloroplast and clostridial type ferredoxin. 

Jones, D.T. and Keis, S. (1995) Origins and relationships of industrial solvent-producing clostridial strains. FEMS Microbiol. Rev., 17, 223-232. 

Johnson JL, Toth J, Santiwatanakul S, Chen J-S (1997) Cultures of Clostridium acetobutylicurrf from various collections comprise Clostridium acetobutylicum, Clostridium beijerinckii, and two other distinct types based on DNA-DNA reassociation. Int J Syst Bacteriol 47 420-424 Jones DT, Keis S (1995) Origins and relationships of industrial solvent-producing clostridial strains. FEMS Microbiol Rev 17 223—232 Jones DT, Woods DR (1986) Acetone-butanol fermentation revisited. Microbiol Rev 50 484-524... 

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