Salt-alkali tolerance, phosphorus-solubilizing ability, and whole genome analysis of Enterobacter cloacae AZ8

Abstract:

Background Soil salinization and available phosphorus deficiency are among the main factors restricting global agricultural development. In this context, the use of functional microorganisms is considered the most promising green improvement solution due to its environmental friendliness and no secondary pollution.Objective Enterobacter cloacae AZ8 is a strain of bacteria isolated by our research group from Egyptian salt-alkali soil samples, with both salt-alkali tolerance and efficient phosphorus solubilization. This study delved into its genome sequence information and molecular mechanisms of salt-alkali tolerance and efficient phosphorus solubilization, aiming to provide a theoretical basis and bacterial resources for salt-alkali soil remediation.Methods This study used the concentration gradient method to test the salt-alkali tolerance of the bacterial strains. The plate method and molybdenum-antimony colorimetric method were employed to preliminarily evaluate the phosphorus-solubilizing effect of the strain. The strain was identified through morphological observation, physiological and biochemical analysis, and 16S rRNA sequencing. Illumina sequencing and PacBio sequencing were employed to obtain the whole genome of AZ8. Bioinformatics methods were used for genome sequence assembly, gene function annotation, and gene prediction to further explore functional genes and elucidate the mechanisms underlying the salt-alkali tolerance and phosphate solubilization of strain AZ8.Results Strain AZ8 grew well under 7.5% NaCl and pH 10.0. It demonstrated significant phosphorus-solubilizing effect, with the highest solubilizing abilities reaching 395.56 μg/mL for organic phosphorus and 363.93 μg/mL for inorganic phosphorus. Whole genome sequencing confirmed that strain AZ8 as E. cloacae and this strain carried multiple phosphorus solubilization-related genes, such as citrate synthase gene (gltA), malate synthase gene (aceB), and inorganic phosphate transport genes (pstA, pstB, pstC, and pstS). In terms of salt-alkali tolerance, the strain carried two Na⁺/H⁺ antiporters NhaA and NhaB, as well as glycine betaine transport-related genes, such as betA, betB, and betT.Conclusion E. cloacae AZ8 has strong salt-alkali tolerance and efficient phosphorus solubilization. Whole genome analysis further reveals the genetic basis and potential mechanisms at the molecular level, providing theoretical guidance for salt-alkali land remediation and phosphorus activation.