Identification of Molecular Pathways Underlying Mn(II) Oxidation in Pseudomonas resinovorans

Manganese oxidation in Pseudomonas resinovorans strain MOB-513 has been previously linked to biofilm formation via the second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP), although the specific molecular components mediating this regulation have not yet been identified. Here we investigate the genetic network underlying Mn(II) oxidation in MOB-513. After transposon mutagenesis, several mutants with differences in Mn(II) oxidation were identified. Targeted analysis of the non-oxidising mutants with Tn insertion disrupting pilC, algR, and hk05390 genes, encoding a core Type IV pilus (Tfp) component, a regulator of pilus biogenesis, and an uncharacterised histidine kinase, respectively, revealed that their phenotype correlated with impaired biofilm formation, reduced intracellular c-di-GMP levels, and decreased Tfp production. We identified two regulators associated with a c-di-GMP-dependent pathway linked to Mn(II) oxidation in MOB-513. The hyper-oxidising strain containing a transposon insertion in the promoter region of the dgc05792 gene showed upregulation of multiple Mn(II)-oxidising enzymes. RR05389 further modulates intracellular c-di-GMP levels and Mn(II) oxidation and functions as a putative cognate response regulator with the histidine kinase HK05390. Together, these results expand our understanding of the molecular pathways underlying Mn(II) oxidation and identify new targets for optimising biological manganese removal.