Reassociation definition

The definition of a species, whether of higher plants, animals, or microorganisms, has as its basis the principle of genetic isolation. Simply put, members of a species are considered interfertile, whereas genetically separate species are not.3 When measurements of DNA reassociation are used to define species, the extent of DNA relatedness expected between members of a species must first be determined. The discussion at the conclusion of this chapter addresses this issue and offers guidelines for predicting genetic relatedness from the extent of DNA complementarity. 

Staekebrandt E, Goebel BM. Taxonomie note a place for DNA-DNA reassociation and 16S rRNA sequence analysis in the present species definition in baeteriology. Int J Syst Baeteriol. 1994 44 846-9. doi 10.1099/00207713 14-4-846. 

Clostridium beijerinckii (one of the molasses-fermenting butanol-producing clostridia) is less well known than C. acetobutylicum because many strains of this species were previously given different species names. Clostridium beijerinckii replaced C. acetobutylicum for commercial solvent production after the corn-based Weizmann process was phased out in the late 1930s (Johnson and Chen 1995 Jones et al. 2000). Many extant strains of C. beijerinckii have been definitively identified by DNA-DNA reassociation or a combination of traits and are available from culture collections (Cummins and Johnson 1971 Johnson et al. 1997 Keis et al. 2001a). 

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