Curtobacterium phyllosphaerae sp. nov. and Curtobacterium guangdongense sp. nov., isolated from the citrus phyllosphere.

Abstract

Two yellow-pigmented, Gram-stain-positive and aerobic bacterial strains, designated RRHDQ10^T and RRHDQ66^T, were isolated from citrus leaves collected from a well-known production area located in Renhua County of Guangdong Province, P. R. China. The 16S rRNA gene comparison showed that strain RRHDQ10^T shared the highest similarity to Curtobacterium ammoniigenes NBRC 101786^T (98.32%) and Curtobacterium albidum DSM 20512^T (98.32%), and strain RRHDQ66^T shared that to Curtobacterium flaccumfaciens JCM 9670^T (99.86%) and Curtobacterium allii 20TX0166^T (99.86%). Phylogenetic analyses based on the 16S rRNA gene and genome sequences showed that they belonged to the genus Curtobacterium, among which strain RRHDQ10^T was most closely related to C. ammoniigenes NBRC 101786^T, and strain RRHDQ66^T showed a close relationship with C. flaccumfaciens JCM 9670^T and Curtobacterium herbarum NBRC 103064^T. The genome-derived average nucleotide identity between the two strains and their closely related type strains was below 82.06% and 85.55%, respectively, and the corresponding digital DNA-DNA hybridization values were below 22.3% and 26.2%, respectively. Anteiso-C_15:0 and iso-C_16: 0 were their major fatty acids. Moreover, summed feature 8 (C_18:1  ω7c and/or C_18:1  ω6c) and anteiso-C_17 : 0 served as major components in strains RRHDQ10^T and RRHDQ66^T, respectively. They took menaquinone-9 (MK-9) as the predominant respiratory quinone and ornithine as the principal cell-wall diamino acid. Their major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and three unidentified glycolipids. The genomic DNA G+C contents of strains RRHDQ10^T and RRHDQ66^T were 71.2 and 70.5 mol%, respectively. Based on phenotypic, genotypic and chemotaxonomic analyses, they should be considered as two novel species of the genus Curtobacterium, for which the names Curtobacterium phyllosphaerae sp. nov. and Curtobacterium guangdongense sp. nov. are proposed, with RRHDQ10^T (=GDMCC 1.2671^T=JCM 34831^T) and RRHDQ66^T (=GDMCC 1.2666^T= JCM 34827^T) as the type strains, respectively.