This study examines the taxonomic classification of the genus Microellobosporia, which was originally placed in the family Actinoplanaceae due to its sporangial spore production. The authors compare Microellobosporia with genera in Streptomycetaceae and Actinoplanaceae using multiple characteristics. They found that Microellobosporia shares identical cell-wall composition (containing hexosamine, alanine, glutamic acid, glycine, and LL-2,6-diaminopimelic acid) with Streptomyces and related genera, but differs from other Actinoplanaceae members. Serological analysis showed that cell-wall antibodies from Streptomyces griseus reacted with polysaccharide extracts of both Microellobosporia strains. Phage susceptibility studies demonstrated that polyvalent actinophages attacking Microellobosporia strains were exclusive to Streptomycetaceae genera, never affecting Actinoplanaceae members. Additionally, Microellobosporia cultures resembled Streptomyces cultures morphologically. The fundamental spore-formation mechanisms in Microellobosporia sporogenic hyphae showed no essential differences from Streptomyces. Based on these convergent biochemical, serological, and phage-susceptibility data, the authors propose transferring Microellobosporia from Actinoplanaceae to the family Streptomycetaceae.

Key findings

• Microellobosporia possesses identical cell-wall composition to Streptomycetaceae genera, containing LL-2,6-diaminopimelic acid and characteristic amino acids
• Cell-wall antigens of Microellobosporia cross-react with Streptomyces griseus antibodies but not with other Actinoplanaceae members
• Polyvalent actinophages show exclusive susceptibility patterns: attacking Microellobosporia only when they also attack Streptomycetaceae, never affecting Actinoplanaceae genera like Streptosporangium or Actinoplanes
• Spore-formation mechanisms in Microellobosporia show no fundamental differences from Streptomyces despite different morphological presentations
• Authors propose reclassifying Microellobosporia from family Actinoplanaceae to Streptomycetaceae based on convergent biochemical and serological evidence