Sixty-eight Actinoplanes isolates from freshwater sediments were compared through 89 unit characters with marker strains of the genera Actinoplanes, Ampullariella, Dactylosporangium, Micromonospora, Planobispora, Spirillospora and Streptosporangium. The data were examined using the simple matching, Jaccard and pattern coefficients and clustering was achieved using the unweighted pair group method with arithmetic averages algorithm. The numerical classification was only marginally affected by the statistics used or by test error, estimated at 5%. Most of the environmental isolates were recovered in five major clusters that were equated with taxospecies. Seven major, nine minor and 29 single-member clusters defined by the S(SM) coefficient at the 83% similarity (S-) level, were assigned to two aggregate groups circumscribed at the 68% S-level. The first cluster group was composed of strains belonging to the genera Actinoplanes (including Ampullariella), Dactylosporangium and Micromonospora and the second included representatives of the genera Planobispora, Planomonospora, Spirillospora and Streptosporangium. Selected Actinoplanes strains subjected to chemical analyses contained complex mixtures of straight- and branched-chain fatty acids, tetrahydrogenated menaquinones with nine isoprene units as the predominant isoprenologue, and major amounts of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol; the representative environmental isolates were also shown to contain meso- and hydroxydiaminopimelic acid; the principal wall sugars were arabinose, galactose, glucose, mannose and xylose. The chemical and numerical taxonomic data support the integrity of established species of Actinoplanes, with the exception of Actinoplanes caeruleus, and show that the five major clusters encompassing environmental isolates merit the rank of species. It is proposed that the five novel taxa be assigned to the genus Actinoplanes as Actinoplanes consettensis sp. nov., Actinoplanes derwentesis sp. nov., Actinoplanes durhamensis sp. nov., Actinoplanes humidus sp. nov., and Actinoplanes palleronii sp. nov. Similarly, the genera Actinoplanes, Dactylosporangium, Micromonospora and Pilimelia have many properties in common and it is proposed that they be classified in the family Micromonosporaceae Krassilnikov 1938; an emended description of this taxon is given. The family Streptosporangiaceae fam. nov. is proposed to accommodate organisms assigned to the genera Microbispora, Microtetraspora, Planobispora, Planomonospora and Streptosporangium.
