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 <i>Hevea brasiliensis</i> plantations in Thailand, two strains, ABSL1-1^T and ABSL49-1^T, were isolated using mineral salts medium with natural rubber as the sole carbon source. Polyphasic taxonomy placed both strains within the genus <i>Gordonia</i>. Strain ABSL1-1^T showed the highest 16S rRNA gene sequence similarity to <i>Gordonia otitidis</i> NBRC 100426^T (98.5%) and <i>Gordonia soli</i> NBRC 108243^T (98.3%), while ABSL49-1^T showed the highest similarity to <i>Gordonia polyisoprenivorans</i> DSM 44302^T (98.4%). The digital DNA-DNA hybridization (dDDH) and average nucleotide identity based on blast values between ABSL1-1^T and closely related type strains were 20.1-20.9%, and 74.1-76.5%, respectively, while those for ABSL49-1^T and closely related type strains were 20.6-22.9%, and 74.3-79.1%, respectively. The cell-wall peptidoglycan of both strains contained <i>meso</i>-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 ABSL1-1^T were C_16:0, and C_18:1 <i> </i>ω<i>9c</i>, while those for ABSL49-1^T were C_16:0, C_18:1 <i> </i>ω<i>9c</i>, summed feature 3 (C_16:1 <i> </i>ω<i>7</i>c/_C16:1 <i> </i>ω<i>6c</i>) and C_18:0 10-methyl. The G+C contents of the genomic DNA of strains ABSL1-1^T and ABSL49-1^T 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 <i>Gordonia</i>, for which the names <i>Gordonia heveisoli</i> sp. nov. (type strain ABSL1-1ᵀ=TBRC 15892ᵀ=NBRC 116252ᵀ) and <i>Gordonia gummivorans</i> sp. nov. (type strain ABSL49-1ᵀ=TBRC 15624ᵀ=NBRC 115559ᵀ) are proposed.