Genomic and Functional Characterization ofPriestia megateriumMOD5IV isolated from the rhizosphere ofCaesalina spinosa(Mol.): Enhancing Phytoremediation Potential in Multi-Metal Contaminated Soils

Heavy metal contamination poses a global threat due to its widespread occurrence and the high toxicity of these elements. Among various methods, phytoremediation has emerged as a preferred approach for the bioremediation of heavy metal-contaminated soils. The search for microorganisms facilitating phytoremediation has become critical to advance ecosystem remediation efforts. Plant growth-promoting bacteria (PGPB) have garnered significant attention in recent decades. In this context, the strain MOD5IV was isolated from the rhizosphere of aCaesalpinia spinosaplant thriving on mining waste in Andacollo, Chile. This strain was initially selected for its plant growth-promoting properties.

This study comprehensively analyzed this strain’s functional and genomic characteristics. MOD5IV exhibited notable PGPB features, including phosphate and potassium solubilization, nitrogen fixation, phytohormone production, and growth promotion ofArabidopsis thaliana. Genomic analysis revealed a chromosome size of 5,254,635 bp and nine distinct plasmids hosting over six thousand genes. Phylogenetic analysis classified the strain within the speciesPriestia megaterium. Functional annotation identified 16 genes associated with tolerance to metals and metalloids, including arsenic (arsB/arsC) and copper (copC/copD), as well as genes conferring resistance to cadmium, lead, mercury, zinc, and cobalt. Accordingly, this strain exhibited robust tolerance to multiple metals, notably copper, arsenic, chromium, cadmium, and lead. Regarding its PGPB capabilities, MOD5IV possesses genes related to siderophore production, nutrient solubilization, IAA synthesis, and nitrogen fixation. Furthermore, MOD5IV promotes the growth ofC. spinosagrown on tailings in laboratory experiments, increasing its capacity to accumulate copper. Overall,Priestia megateriumMOD5IV exhibits promising traits for microbe-assisted phytoremediation of metal-contaminated soils.