Methylobacterium litchii sp. nov., Methylobacterium guangdongense sp. nov. and Methylorubrum subtropicum sp. nov., isolated from the phyllosphere of litchi.

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Three aerobic, pink-pigmented, Gram-negative, motile and rod-shaped bacterial strains, designated SD21T, SI9T and SB2T, were isolated from the phyllosphere of healthy litchis collected from three main producing sites of Guangdong Province, PR China. The 16S rRNA gene analysis showed that strains SD21T and SI9T belonged to the genus Methylobacterium (Mtb.) with the highest similarity to Mtb. komagatae DSM 19563T (98.7%) and Mtb. phyllosphaerae CBMB27T (99.8%), respectively, while strain SB2T belonged to the genus Methylorubrum (Mtr.) and showed the highest similarity to Mtr. suomiense DSM 14458T (98.6%). Phylogenomic analysis based on 92 core genes clearly showed that the most closely related type strains of SD21T, SI9T and SB2T were Mtb. komagatae DSM 19563T, Mtb. phyllostachyos ICMP 17619T and Mtr. salsuginis CGMCC 1.6474T, respectively. The ANI and dDDH values between the three isolates and their most closely related type strains were 85.6‒90.1% and 29.5‒40.4%, respectively, much below the threshold values for species delimitation. The isolates showed clear differences from their closely related type strains in terms of growth conditions, enzyme activities, substrates assimilation and contents of the major fatty acids. They all took summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) as the major fatty acid, ubiquinone 10 as the predominant respiratory quinone and phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine as the major polar lipids. The phenotypic, phylogenetic and chemotaxonomic analyses with genome comparison strongly support that the isolates represent three distinct novel species within the genera of Methylobacterium and Methylorubrum, for which the names Methylobacterium litchii sp. nov., Methylobacterium guangdongense sp. nov. and Methylorubrum subtropicum sp. nov. are proposed, with SD21T (=GDMCC 1.4327T=KCTC 8300T), SI9T (=GDMCC 1.4329T=KCTC 8298T) and SB2T (=GDMCC 1.4328T=KCTC 8299T) as the type strains, respectively.