Abstract
A gram-negative, nitrogen-fixing, rod-shaped, and motile bacterium, designated as ZJS20(T), was isolated from the sediments of Aegiceras corniculatum in Zhanjiang, Guangdong, China. The growth of strain ZJS20(T) occurred at 10°C-45°C, pH 5.5-8.0, and in 0%-3% (wt/vol) NaCl. Strain ZJS20(T) had the highest sequence similarity of 16S rRNA gene with Pseudaeromonas paramecia PCS8(T) (98.5%), followed by Pseudaeromonas sharmana GPTSA-6(T) (97.1%) and Pseudaeromonas pectinilytica AR1(T) (96.7%). The phylogenetic trees built using 16S rRNA genes and Type (Strain) Genome Server both revealed that strain ZJS20(T) fell into a cluster with Pseudaeromonas sp. strains. The genome of strain ZJS20(T) has a 3,681,671 bp circular chromosome, a G + C content of 62.7%, and 3,320 proteins-coding genes. The genome contains nif and anf genes for the synthesis of Mo- and Fe-nitrogenase and genes related to plant growth-promoting traits. Both the digital DNA-DNA hybridization and average nucleotide identity values between strain ZJS20(T) and type strains of the genus Pseudaeromonas were below the cutoff thresholds for species demarcation. The profiles of the predominant fatty acids, major polar lipids, and respiratory quinone of strain ZJS20(T) were similar to those of other Pseudaeromonas species. According to the above results, strain ZJS20(T) is considered to be a novel species of the genus Pseudaeromonas, with the proposed name Pseudaeromonas aegiceratis sp. nov. The type strain is ZJS20(T) (MCCC 1K08760(T) = KCTC 8214(T)). This study expands the membership of the genus Pseudaeromonas and reveals the potential of this genus to be used as plant growth-promoting bacteria with their outstanding nitrogen-fixation ability.IMPORTANCEPseudaeromonas is a genus known as close to the genus Aeromonas and contains only three species, which were isolated from different sources. Except for the physio-biochemical properties, other characteristics, such as genomic information and functions of the genus, have been reported scarcely to date. Here, the study reports the fourth species (Pseudaeromonas aegiceratis ZJS20(T)) to the genus Pseudaeromonas and reveals its nitrogen-fixation capacity. Comparative genomic analyses revealed that genomes of strain ZJS20(T) and other type Pseudaeromonas strains all contain nif genes (nifBHDKENXV) for the synthesis of Mo-nitrogenase, as well as genes related to phosphate metabolism and auxin synthesis. Therefore, we proposed that Pseudaeromonas sp. could be considered as a new and potential plant growth-promoting bacteria to be used in agriculture, although in-depth experiments are needed in the future to verify their specific plant growth-promoting traits.