Is characterization of a single isolate sufficient for valid publication of a new genus or species? Proposal to modify Recommendation 30b of the Bacteriological Code (1990 Revision)

From 1990 to 2000, the number of published named taxa based upon new isolat es at species and genus levels in International Journal of Systematic and E volutionary Microbiology, formerly international Journal of Systematic Bact eriology, have increased by approximately four- and sevenfold,, respectivel y. New taxa based upon characterization of only a single isolate remained a t around 40% for both categories. The Bacteriological Code (1990 Revision) has no recommendations on the number of strains required for definition of new taxa. For a few groups, a minimum number of 5-10 strains has been sugge sted in minimal standards. Since an exponential increase in new taxa can be expected in the future, the authors discuss problems related to naming new species and genera based upon descriptions of a single isolate and suggest that this practice is re-evaluated. It is proposed that the following shou ld be added to Recommendation 30b of the Bacteriological Code: 'Description s should be based on as many strains as possible (minimum five), representi ng different sources with respect to geography and ecology in order to be w ell characterized both phenotypically and genotypically, to establish the c entre (from which the type strain could be chosen) and the extent of the cl uster to be named. In addition, comparative studies should be performed, in cluding reference strains that represent neighbouring species and/or genera , in order to give descriptions that are sufficiently detailed to allow dif ferentiation from these neighbours'.