Cytobacillus citreus sp. nov., isolated from citrus rhizosphere soil

Abstract

A Gram-stain-positive, rod-shaped and motile strain, designated FJAT-49705^T, was isolated from the citrus rhizosphere soil sample. Strain FJAT-49705^T grew at 20-40 °C (optimum, 30 °C) and pH 6.0-11.0 (optimum, pH 7.0) with 0-5 % (w/v) NaCl (optimum, 2 %). Strain FJAT-49705^T showed high 16S rRNA gene sequence similarity to 'Bacillus dafuensis' FJAT-25496^T (99.7 %) and Cytobacillus solani FJAT-18043^T (98.0 %). In phylogenetic (based on 16S rRNA gene sequences) and phylogenomic trees (based on 71 bacterial single-copy genes), strain FJAT-49705^T clustered with the members of the genus Cytobacillus. MK-7 was the only isoprenoid quinone present. The main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid. The major fatty acids were anteiso-C_{15 : 0} and iso-C_{15 : 0}. The genomic DNA G+C content was 36.9 %. The average nucleotide identity (ANI) values between FJAT-49705^T and 'B. dafuensis' FJAT-25496^T and C. solani FJAT-18043^T were below the cut-off level (95-96 %) recommended as the ANI criterion for interspecies identity. Based on the above results, strain FJAT-49705^T represents a novel species of the genus Cytobacillus, for which the name Cytobacillus citreus sp. nov. is proposed. The type strain is FJAT-49705^T (=CCTCC AB 2019243^T= LMG 31580^T).

Keywords: Cytobacillus citreus sp. nov.; citrus field; polyphasic taxonomy; rhizosphere.