Gordonia heveisoli sp. nov. and Gordonia gummivorans sp. nov., two natural rubber-degrading actinobacteria isolated from soil in Hevea brasiliensis plantations.

During a survey for natural-rubber-degrading actinobacteria associated with soils from Hevea brasiliensis plantations in Thailand, two strains, ABSL1-1T and ABSL49-1T, were isolated using mineral salts medium with natural rubber as the sole carbon source. Polyphasic taxonomy placed both strains within the genus Gordonia. Strain ABSL1-1T showed the highest 16S rRNA gene sequence similarity to Gordonia otitidis NBRC 100426T (98.5%) and Gordonia soli NBRC 108243T (98.3%), while ABSL49-1T showed the highest similarity to Gordonia polyisoprenivorans DSM 44302T (98.4%). The digital DNA-DNA hybridization (dDDH) and average nucleotide identity based on blast values between ABSL1-1T and closely related type strains were 20.1-20.9%, and 74.1-76.5%, respectively, while those for ABSL49-1T and closely related type strains were 20.6-22.9%, and 74.3-79.1%, respectively. The cell-wall peptidoglycan of both strains contained meso-diaminopimelic acid and the whole-cell sugars comprised ribose, arabinose, galactose and glucose. Both strains contained MK-9(H2) as the major menaquinone and phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside were detected as the polar lipids. The predominant fatty acids of ABSL1-1T were C16:0, and C18:1  ω9c, while those for ABSL49-1T were C16:0, C18:1  ω9c, summed feature 3 (C16:1  ω7c/C16:1  ω6c) and C18:0 10-methyl. The G+C contents of the genomic DNA of strains ABSL1-1T and ABSL49-1T were 67.0 mol% and 66.0 mol%, respectively. Based on the results of a polyphasic taxonomic analysis, strains ABSL1-1ᵀ and ABSL49-1ᵀ represent the type strains of two novel species of the genus Gordonia, for which the names Gordonia heveisoli sp. nov. (type strain ABSL1-1ᵀ=TBRC 15892ᵀ=NBRC 116252ᵀ) and Gordonia gummivorans sp. nov. (type strain ABSL49-1ᵀ=TBRC 15624ᵀ=NBRC 115559ᵀ) are proposed.