Isolation and pan-genome analysis of Acinetobacter junii SC22, a heavy metal(loid)s resistant and plant growth promoting bacterium, from the Zijin Gold and Copper mine

Excess heavy metals can be toxic to plants and microbes. The application of plant growth promoting bacteria (PGPB) in agriculture has gained global attention for promising sustainable development, including in heavy metals polluted soil. However, the metal resistance and plant growth promoting determinants of strains belonging to the genus Acinetobacter remain poorly understood. Here, we characterize strain SC22, and analyzed the complete genome of strain SC22. The influence of inoculating with this strain on soybean growth by pot experiment was also analyzed. Our results showed that strain SC22 displayed high As(III) and Cu(II) resistance and high IAA production. The presence of operons such as, merRACDT, zntA and 4 znuABC, czcABCD and arsRBCH, and trpRABCDFS encode functions enabling strain SC22 to survive under extremely highly heavy metal contaminated environments and also produce plant hormones. The inoculation of strain SC22 stimulated soybean growth. Strains belonging to the genus Acinetobacter have an open pan-genome, and ArsH encoded on the core genome displayed differences to ArsH encoded on the genome of other Acinetobacter that were isolated from different habitats. These findings suggest the potential use of strain Acinetobacter junii SC22 in bioremediation and subsequent plant growth promotion in heavy metal polluted environments.