Rowbotham and Cross describe the characterization and formal naming of Rhodococcus coprophilus sp. nov., a previously unnamed aerobic actinomycete known informally as 'Lspi' (Large spored pink irregular). The organism was commonly isolated from herbivore dung and aquatic habitats. Using numerical taxonomic analysis, the authors examined 36 bacterial strains and found that Lspi strains formed a homogeneous cluster distinct from related nocardioforms at the 69% similarity level. Based on morphological, chemotaxonomic, and numerical analyses, they assigned Lspi to the 'rhodochrous' complex within the genus Rhodococcus. The organism exhibits characteristic features including coccoid cells derived from fragmenting mycelium, orange-red pigmented colonies with central papillae, partial photochromogenicity, and a requirement for thiamin. Whole-cell chemotaxonomy revealed meso-diaminopimelic acid and type IV cell wall composition typical of the rhodochrous group. The authors also propose that the genus Rhodococcus be applied to most species within the poorly defined 'rhodochrous' complex, rather than their previous scattered classification among Nocardia, Mycobacterium, Jensenia, Corynebacterium, and Gordona. Strain CUB687 was designated as the type strain.

Key findings

• Lspi strains form a distinct homogeneous cluster separated from other nocardioforms at 69% similarity in numerical taxonomy analysis, warranting recognition as a new species Rhodococcus coprophilus
• Lspi morphology is characteristic: cells are Gram-positive cocci with coccoid elements derived from fragmenting mycelium, orange-red colonies with central papillae, and require thiamin for optimal growth
• Chemotaxonomic analysis confirms type IV cell wall composition with meso-diaminopimelic acid, arabinose, and galactose; mycolic acid mobility and DNA GC content (60-64 mol%) align with the rhodochrous complex
• The genus Rhodococcus is proposed as appropriate for accommodating most species in the ill-defined 'rhodochrous' complex, consolidating strains previously scattered among multiple genera including Nocardia, Mycobacterium, and Jensenia