Affiliation:
1. Key Laboratory of Agricultural Microbiomics and Precision Application (MARA), Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Key Laboratory of Agricultural Microbiome (MARA), State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, PR China
2. College of Plant Protection, South China Agricultural University, Guangzhou 510642, PR China
Abstract
Three novel Gram-stain-positive, aerobic and rod-shaped bacterial strains, designated RHCKG28T, RHCJP20T and RHCKG23T, were isolated from phyllosphere of healthy citrus leaves collected from Renhua County in Guangdong Province, PR China. 16S rRNA gene sequences comparison and phylogenetic analyses showed that they all belonged to the genus
Curtobacterium
, among which strain RHCKG28T showed the highest similarity to
Curtobacterium herbarum
NBRC 103064T (99.3 %), while strains RHCJP20T and RHCKG23T showed 99.2 and 99.0 % similarity to
Curtobacterium citreum
JCM 1345T, respectively. Phylogenomic analysis showed that the three novel strains were most closely related to
C. citreum
JCM 1345T and
Curtobacterium albidum
JCM 1344T. The novel strains could be distinguished from their closely related type strains in terms of enzyme activities, substrate assimilation and fatty acid profiles. In addition, the average nucleotide identity and digital DNA–DNA hybridization values between the novel strains and closely related type strains were 84.4‒89.5 % and 24.5‒34.1 %, respectively, which were below the threshold values for species delimitation. They all took anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0 as the major fatty acids, menaquinone 9 (MK-9) as the sole predominant respiratory quinone, and ornithine as the principal cell-wall diamino acid. The major polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol and several unidentified glycolipids. The phenotypic, genotypic and chemotaxonomic data supported that they represent three distinct novel species of the genus
Curtobacterium
, for which the names Curtobacterium caseinilyticum sp. nov., Curtobacterium subtropicum sp. nov. and Curtobacterium citri sp. nov. are proposed, with RHCKG28T (=GDMCC 1.2667T=JCM 34828T), RHCJP20T (=GDMCC 1.2668T=JCM 34829T) and RHCKG23T (=GDMCC 1.2669T=JCM 34830T) as the type strains, respectively.
Funder
the Science and Technology Program of Guangdong Province
the GDAS’ Project of Science and Technology Development
the Guangdong Strategic Special Fund for Rural Revitalization
the Guangdong Special Support Program
Subject
General Medicine,Ecology, Evolution, Behavior and Systematics,Microbiology