Rhodococcus folensis sp. nov., an orange-red-pigmented bacterium from mining soil

Abstract

Abstract Mining-impacted environments represent chemically complex ecosystems that may harbor metabolically versatile and pigment-producing microorganisms. During a survey of pigment-producing bacteria from abandoned mining soil in Trabzon, Türkiye, a red-pigmented strain, designated FMA22 T , was isolated and characterized using a polyphasic taxonomic approach. 16 S rRNA gene sequence analysis placed the strain within the genus Rhodococcus , showing the highest similarity to R. corynebacterioides DSM 20,151 T (99.57%), R. kroppenstedtii DSM 44908ᵀ (99.06%) and R. trifolii T8 T (98.96%). The strain was Gram-stain-positive, aerobic and non-motile, and grew at 4–40 °C. Polar lipids included phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, phosphatidylcholine, five unidentified glycolipids, four unidentified lipids, one unidentified phospholipid and one unidentified phosphoglycolipid; MK-8(H2) was the major respiratory quinone. Major fatty acids were C18:1 ω9c, summed feature 3 (C16:1 ω7c/C16:1 ω6c) and C16:0. ANI and dDDH values with the closest relatives were below 76.8% and 20.5%, respectively. The draft genome (4.23 Mb; 67.2 mol% G + C; 4,106 CDSs) harbors a terpene-associated carotenoid cluster containing crtB, crtI and crtY. The orange-red pigment (λmax = 475 nm) showed antioxidant activity (DPPH SC₅₀ = 5.38 mg mL⁻¹; FRAP = 4.34 µmol TE g⁻¹) and weak but measurable HIV-1 reverse transcriptase inhibition (IC₅₀ = 22 mg mL⁻¹). These data support the proposal of Rhodococcus folensis sp. nov., with FMA22ᵀ (= LMG 34144ᵀ = DSM 120048ᵀ) as the type strain.