Metapseudomonas phytobenefica sp. nov. and Metapseudomonas cellulosilytica sp. nov., two potential novel plant-beneficial bacteria isolated from rhizosphere soil of citrus plants

Two potential novel plant-beneficial bacteria, designated CR1201^T and CR3202^T, were isolated from the rhizosphere soil of citrus in Deqing county, located in Zhaoqing, Guangdong Province, PR China. They could produce indole-3-acetic acid and siderophores. Cells of the two novel strains were Gram-stain-negative, motile with polar flagella, aerobic and non-spore-forming rods. Strain CR1201^T showed high antagonistic activity against the citrus canker pathogen <i>Xanthomonas citri</i> subsp. <i>citri</i>. Phylogenetic analyses based on 16S rRNA gene sequences and 92 core genes showed that strains CR1201^T and CR3202^T belonged to the genus <i>Metapseudomonas</i> and were most closely related to the four validly published species <i>Metapseudomonas lalkuanensis</i> PE08^T, <i>Metapseudomonas boanensis</i> DB1^T, <i>Metapseudomonas furukawaii</i> KF707^T and <i>Metapseudomonas resinovorans</i> LMG 2274^T. The average nucleotide identity and digital DNA-DNA hybridization values between the two isolates and their most closely related type strains were 80.06-92.76% and 19.2-49.8%, respectively, which were well below the threshold values for species delimitation. The genomic DNA G+C content of strains CR1201^T and CR3202^T was 64.5 mol% for both strains. The major fatty acids of strain CR1201^T were identified as summed feature 8 (C_18:1 <i> ω</i>7c and/or C_18:1 <i> ω</i>6c), C_16:0 and C_17:0 cyclo, whereas those of strain CR3202^T were identified as summed feature 8 (C_18:1 <i>ω</i>7c), summed feature 3 (C_16:1 <i>ω</i>7c and/or C_16:1 <i>ω</i>6c) and C_16:0. The predominant quinone for both strains was ubiquinone 10. The polar lipids comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminophospholipid and an unidentified phospholipid. Based on the phenotypic, genotypic, chemotaxonomic analyses and genome comparison, strains CR1201^T and CR3202^T were identified as two novel species within the genus <i>Metapseudomonas</i>, for which the names <i>Metapseudomonas phytobenefica</i> sp. nov. and <i>Metapseudomonas cellulosilytica</i> sp. nov. are proposed, with CR1201^T (=GDMCC 1.4560^T=JCM 37070^T) and CR3202^T (=GDMCC 1.4918^T=CCM 9447^T) as the type strains, respectively.