Cr(III) Oxidation and Cr Toxicity in Cultures of the Manganese(II)-Oxidizing<i>Pseudomonas putida</i>Strain GB-1

Murray, Karen J.; Mozafarzadeh, Mylene L.; Tebo, Bradley M.

doi:10.1080/01490450590945988

Cited by 51 publications

(45 citation statements)

References 37 publications

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“…In this defined artificial seawater medium, SG-1 can recycle Mn quickly to oxidize large amounts of Cr(III) (e.g., Figure 1), which supports the idea that the presence of Mn(II)-oxidizing bacteria should be considered when determining the environmental fate of Cr-even when only trace amounts of Mn are present. In environmental systems which contain many more potential organic ligands for the Cr(III), Cr oxidation could be even faster, similar to what was seen with studies of Pseudomonas in two different freshwater media (15). Mn(II)-oxidizing bacteria are found in a variety of environments, and can oxidize Mn(II) even when levels of O 2 are extremely low (37), so any Cr(III) that is present has the potential to be rapidly, though indirectly, oxidized by these bacteria.…”

Section: Resultssupporting

confidence: 73%

“…Comparisons to synthetic oxides showed that this oxide was more similar to vernadite and acid birnessite than to the more crystalline synthetic triclinic birnessite. The biological Mn oxides produced by Pseudomonas putida have been shown to oxidize Cr(III) to Cr(VI) (15,16). Surprisingly, in growth medium with low levels of organics, the Cr(VI) produced was less toxic to the bacteria than the original Cr(III) (15).…”

Section: Introductionmentioning

confidence: 99%

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Cr(III) Is Indirectly Oxidized by the Mn(II)-Oxidizing Bacterium Bacillus sp. Strain SG-1

Murray

Tebo

2006

Environ. Sci. Technol.

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Manganese oxides are the only known oxidants of Cr(III) in the environment, and predictions of the fate of Cr(III) have been based on Cr(III) oxidation rates with well-characterized Mn(III,IV) oxide minerals. Our research, however, indicates that the presence of Mn(II)-oxidizing bacteria, may accelerate these rates through the production of very reactive Mn oxides or intermediates formed in the oxidation process. Experiments with the Mn(II)-oxidizing Bacillus sp. strain SG-1 show that this bacterium can accelerate Cr(III) oxidation compared to both abiotic and biologically produced Mn oxides. Initial rates of Cr(III) oxidation by biogenic oxides were approximately 7 times faster than Cr(III) oxidation rates by equivalent amounts of synthetic δ-MnO 2 and 25 times faster by SG-1 spores with Mn(II). Cr(III) oxidation by SG-1 is not direct; Mn is required, but only in small amounts, indicating that it is recycled. Cr(III) oxidation is inhibited above 5 μM dissolved Mn(II), while Mn(II) oxidation is not, suggesting that the processes are controlled by different mechanisms. These results illustrate the need to consider bacterial activity and the concentration of Mn when predicting the potential for Cr(III) oxidation.

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Section: Resultssupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Cr(III) Is Indirectly Oxidized by the Mn(II)-Oxidizing Bacterium Bacillus sp. Strain SG-1

Murray

Tebo

2006

Environ. Sci. Technol.

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“…SG-1 is a convenient model organism for enzymatic Mn(II) oxidation due to the oxidation occurring while the cells are in a nonvegetative state excluding the complications from growth and metabolism. However, Mn(II) oxidation is widespread (23), and indirect Cr(III) oxidation has been shown in Pseudomonas putida, which oxidizes Mn(II) during late log phase (17,32). It is possible that Co(II) could be indirectly oxidized by other Mn(II)-oxidizing bacteria.…”

Section: Discussionmentioning

confidence: 99%

Indirect Oxidation of Co(II) in the Presence of the Marine Mn(II)-Oxidizing Bacterium Bacillus sp. Strain SG-1

Murray

Webb

Bargar

et al. 2007

Appl Environ Microbiol

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Cobalt(II) oxidation in aquatic environments has been shown to be linked to Mn(II) oxidation, a process primarily mediated by bacteria. This work examines the oxidation of Co(II) by the spore-forming marine Mn(II)-oxidizing bacterium Bacillus sp. strain SG-1, which enzymatically catalyzes the formation of reactive nanoparticulate Mn(IV) oxides. Preparations of these spores were incubated with radiotracers and various amounts of Co(II) and Mn(II), and the rates of Mn(II) and Co(II) oxidation were measured. Inhibition of Mn(II) oxidation by Co(II) and inhibition of Co(II) oxidation by Mn(II) were both found to be competitive. However, from both radiotracer experiments and X-ray spectroscopic measurements, no Co(II) oxidation occurred in the complete absence of Mn(II), suggesting that the Co(II) oxidation observed in these cultures is indirect and that a previous report of enzymatic Co(II) oxidation may have been due to very low levels of contaminating Mn. Our results indicate that the mechanism by which SG-1 oxidizes Co(II) is through the production of the reactive nanoparticulate Mn oxide.

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“…Identifying signals or conditions that regulate oxidation could provide some insight into the role of Mn(II) oxidation in the cell. Aside from a requirement for oxygen (28) and iron (27,30), as well as the observation that oxidation occurs in stationary phase (23), very little is known about this regulation.…”

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Identification of a Two-Component Regulatory Pathway Essential for Mn(II) Oxidation in Pseudomonas putida GB-1

Geszvain

Tebo

2010

Appl Environ Microbiol

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Bacterial manganese(II) oxidation has a profound impact on the biogeochemical cycling of Mn and the availability of the trace metals adsorbed to the surfaces of solid Mn(III, IV) oxides. The Mn(II) oxidase enzyme was tentatively identified in Pseudomonas putida GB-1 via transposon mutagenesis: the mutant strain GB-1-007, which fails to oxidize Mn(II), harbors a transposon insertion in the gene cumA. cumA encodes a putative multicopper oxidase (MCO), a class of enzymes implicated in Mn(II) oxidation in other bacterial species. However, we show here that an in-frame deletion of cumA did not affect Mn(II) oxidation. Through complementation analysis of the oxidation defect in GB-1-007 with a cosmid library and subsequent sequencing of candidate genes we show the causative mutation to be a frameshift within the mnxS1 gene that encodes a putative sensor histidine kinase. The frameshift mutation results in a truncated protein lacking the kinase domain. Multicopy expression of mnxS1 restored Mn(II) oxidation to GB-1-007 and in-frame deletion of mnxS1 resulted in a loss of oxidation in the wild-type strain. These results clearly demonstrated that the oxidation defect of GB-1-007 is due to disruption of mnxS1, not cumA::Tn5, and that CumA is not the Mn(II) oxidase. mnxS1 is located upstream of a second sensor histidine kinase gene, mnxS2, and a response regulator gene, mnxR. In-frame deletions of each of these genes also led to the loss of Mn(II) oxidation. Therefore, we conclude that the MnxS1/MnxS2/MnxR two-component regulatory pathway is essential for Mn(II) oxidation in P. putida GB-1.

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Cr(III) Oxidation and Cr Toxicity in Cultures of the Manganese(II)-OxidizingPseudomonas putidaStrain GB-1

Cited by 51 publications

References 37 publications

Cr(III) Is Indirectly Oxidized by the Mn(II)-Oxidizing Bacterium Bacillus sp. Strain SG-1

Cr(III) Is Indirectly Oxidized by the Mn(II)-Oxidizing Bacterium Bacillus sp. Strain SG-1

Indirect Oxidation of Co(II) in the Presence of the Marine Mn(II)-Oxidizing Bacterium Bacillus sp. Strain SG-1

Identification of a Two-Component Regulatory Pathway Essential for Mn(II) Oxidation in Pseudomonas putida GB-1

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