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 DMYE4T and HJE1T, 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 DMYE4T 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 HJE1T 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 DMYE4T and HJE1T belonged to the genus Pantoea and were most closely related to Pantoea vagans LMG 24199T and Pantoea rodasii LMG 26273T, respectively. The genome-derived average nucleotide identity values between the novel strains and their closely related type strains were 87.72-94.59% (DMYE4T) and 83.52-88.86% (HJE1T), 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 C16 : 0, summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c) and summed feature 8 (C18 : 1  ω7c and/or C18 : 1  ω6c). The genomic DNA G+C contents of strains DMYE4T and HJE1T were 55.05 and 53.86 mol%, respectively. Based on this polyphasic taxonomic study, strains DMYE4T and HJE1T 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 DMYE4T (=GDMCC 1.4184T=JCM 36484T) and HJE1T (=GDMCC 1.4186T=JCM 36485T).