Effects of exogenous pyoverdines on Fe availability and their impacts on Mn(II) oxidation by Pseudomonas putida GB-1

Abstract

Pseudomonas putida GB-1 is a Mn(II)-oxidizing bacterium that produces pyoverdine-type siderophores (PVDs), which facilitate the uptake of Fe(III) but also influence MnO2 formation. Recently, a non-ribosomal peptide synthetase mutant that does not synthesize PVD was described. Here we identified a gene encoding the PVDGB-1 (PVD produced by strain GB-1) uptake receptor (PputGB1_4082) of strain GB-1 and confirmed its function by in-frame mutagenesis. Growth and other physiological responses of these two mutants and of wild type were compared during cultivation in the presence of three chemically distinct sets of PVDs (siderotypes n°1, n°2, and n°4) derived from various pseudomonads. Under iron-limiting conditions, Fe(III) complexes of various siderotype n°1 PVDs (including PVDGB-1) allowed growth of wild type and the synthetase mutant, but not the receptor mutant, confirming that iron uptake with any tested siderotype n°1 PVD depended on PputGB1_4082. Fe(III) complexes of a siderotype n°2 PVD were not utilized by any strain and strongly induced PVD synthesis. In contrast, Fe(III) complexes of siderotype n°4 PVDs promoted the growth of all three strains and did not induce PVD synthesis by the wild type, implying these complexes were utilized for iron uptake independent of PputGB1_4082. These differing properties of the three PVD types provided a way to differentiate between effects on MnO2 formation that resulted from iron limitation and others that required participation of the PVDGB-1 receptor. Specifically, MnO2 production was inhibited by siderotype n°1 but not n°4 PVDs indicating PVD synthesis or PputGB1_4082 involvement rather than iron-limitation caused the inhibition. In contrast, iron limitation was sufficient to explain the inhibition of Mn(II) oxidation by siderotype n°2 PVDs. Collectively, our results provide insight into how competition for iron via siderophores influences growth, iron nutrition and MnO2 formation in more complex environmental systems.

Mn(II) Oxidation by the Multicopper Oxidase Complex Mnx: A Coordinated Two-Stage Mn(II)/(III) and Mn(III)/(IV) Mechanism

“…There are many bacterially produced chelating agents, some of which are no doubt responsible for significant Mn­(III) concentrations frequently encountered in a variety of environments. − As demonstrated with PP, MnO 2 formation can be suppressed altogether at sufficiently high chelator concentrations. A case in point is the finding that MnO 2 formation is suppressed in P. putida GB-1, under conditions of iron limitation, due to the expression of the siderophore pyoverdine, which has a stronger affinity for Mn­(III) than for Fe­(III). − …”

Microbial ligand coordination: Consideration of biological significance

“…The speciation of the ferric and manganic citrate complexes was not described [28], and thus is Production of PVD GB1 along with other PVD-type siderophores have been linked to regulation of MnO 2 formation and biofilm production [47,48]. Rhizoferrin ( Figure 3) is a siderophore produced by the fungus Rhizopus arrhizus and by the bacterium Ralstonia picketti [49,50].…”

Effect of Cu(II) and Conserved Copper Binding Sites on Multicopper Oxidase CopA and Characterization of the BioMnOx

“…It is reported that many metal ions could affect the oxidizing activity of MCO, one of which is Cu( ) (Butter eld and Tebo 2017; El Gheriany et al 2009; Lee et al 2014). Many results have been observed that MCOs binds much more Cu than necessary to ll the four Cu sites (Butter eld and Tebo 2017; Musci et al 1993;Roberts et al 2003).…”