Nocardia flavorosea sp. nov.

This study describes the formal recognition of Nocardia flavorosea sp. nov., a soil-derived actinomycete strain (JCM 3332T) previously identified informally by Liu et al. in 1983. Researchers employed multiple approaches to establish this as a distinct species: 16S rDNA sequencing, phylogenetic analysis using four tree-making algorithms, DNA-DNA hybridization, and comprehensive phenotypic characterization. Although the strain clusters phylogenetically with Nocardia carnea based on 16S rRNA sequences (99.2% similarity with 100% bootstrap support), DNA-DNA relatedness studies revealed only 2-5% homology between the two organisms, confirming they represent separate genomic species. The new isolate was distinguished from all eleven previously validated Nocardia species using phenotypic properties. N. flavorosea is an aerobic, Gram-positive, partially acid-alcohol-fast actinomycete producing orange substrate mycelium with white to pinkish aerial hyphae. Key characteristics include growth between 25-50°C, degradation of starch but not adenine or casein, and specific fatty acid and mycolic acid profiles typical of Nocardia. The type strain is JCM 3332T, isolated from soil in Yunnan Province, China, with a DNA G+C content of 69 mol%.

Key findings

• Strain JCM 3332T merits recognition as a new species, Nocardia flavorosea sp. nov., based on genotypic and phenotypic data distinguishing it from all eleven previously described Nocardia species
• Although 16S rRNA sequence analysis groups the strain with N. carnea (99.2% similarity), DNA-DNA hybridization showed only 2-5% relatedness, confirming separate genomic species status
• N. flavorosea exhibits characteristic Nocardia chemotaxonomic properties including mycolic acids with 50-56 carbon atoms, specific fatty acid composition, and wall components typical of the genus
• Phenotypic differentiation is evident through unique combinations of substrate degradation patterns, biochemical tests, and growth characteristics, particularly acid production from dulcitol