Three actinomycetes designated A294, A385 and A448 all produced novel
inhibitors of an enzyme involved in the regulation of mammalian choles
terol metabolism. The organisms were identified as members of the genu
s Actinoplanes using morphological and chemotaxonomic characters. Nume
rical phenetic data obtained for clusters defined at the 77.5% S-sm si
milarity level in the taxonomic study of Actinoplanes and related taxa
by Goodfellow et al. [6], was used to construct a probabilistic ident
ification matrix for the genus Actinoplanes. This was in an attempt to
characterise the producing strains to species level. Identification s
cores for the three organisms, together with two type strains, were de
termined using the MATIDEN program of Sneath [36]. Strains A294 and A3
85 did not identify correctly with any cluster. Strain A448 was identi
fied as Actinoplanes derwentensis. The two type strains identified wit
hin acceptable statistical limits to their correct clusters. Due to th
e absence of other taxonomic criteria with which to speciate members o
f the genus Actinoplanes we recommend that the two unidentified produc
ing strains should be considered novel until such time as further tech
niques become available.