Pantoea citricola sp. nov. and Pantoea folii sp. nov., two bacteria with plant-growth-promoting traits isolated from the phyllosphere of honey pomelo (Citrus maxima)

Two yellow-pigmented, Gram-negative, facultatively anaerobic, motile and rod-shaped bacterial strains, designated DMYE4 T and HJE1 T , were isolated from healthy leaves of honey pomelo ( Citrus maxima ) in Dabu County, Guangdong Province, PR China. Both strains could produce siderophore and solubilize inorganic phosphate, implicating promising potential in promoting plant growth. Strain DMYE4 T could grow at 15‒37 °C (optimum at 28‒30 °C) and pH 5.0‒8.0 (optimum, pH 5.0) in the presence of 0‒7.0% (w/v) NaCl (optimum, 1.0–3.0%), while strain HJE1 T grew at 10‒37 °C (optimum, 28‒30 °C) and pH 5.0‒8.0 (optimum, pH 5.0) in the presence of 0‒10.0% (w/v) NaCl (optimum, 0%). Phylogenetic analyses based on 16S rRNA gene and genome sequences supported that strains DMYE4 T and HJE1 T belonged to the genus Pantoea and were most closely related to Pantoea vagans LMG 24199 T and Pantoea rodasii LMG 26273 T , respectively. The genome-derived average nucleotide identity values between the novel strains and their closely related type strains were 87.72–94.59% (DMYE4 T ) and 83.52–88.86% (HJE1 T ), and the corresponding digital DNA–DNA hybridization values were 33.9–58.6% and 27.4–36.7%, respectively, which were all below the suggested thresholds recommended for new prokaryotic taxa delimitation. Both strains contained ubiquinone 8 as the predominant respiratory quinone, and their major fatty acids (>10% of the total amount) were C 16 : 0 , summed feature 3 (C 16 : 1 ω 7c and/or C 16 : 1 ω 6 c ) and summed feature 8 (C 18 : 1 ω 7 c and/or C 18 : 1 ω 6 c ). The genomic DNA G+C contents of strains DMYE4 T and HJE1 T were 55.05 and 53.86 mol%, respectively. Based on this polyphasic taxonomic study, strains DMYE4 T and HJE1 T represent two distinct novel species within the genus Pantoea , for which the names Pantoea citricola sp. nov. and Pantoea folii sp. nov. are proposed, respectively. The type strains are DMYE4 T (=GDMCC 1.4184 T =JCM 36484 T ) and HJE1 T (=GDMCC 1.4186 T =JCM 36485 T ).