Production of Manganese Oxide Nanoparticles by Shewanella Species

Abstract

Several species of the bacterial genus Shewanella are well-known dissimilatory reducers of manganese under anaerobic conditions. In fact, Shewanella oneidensis is one of the most well studied of all metal-reducing bacteria. In the current study, a number of Shewanella strains were tested for manganese-oxidizing capacity under aerobic conditions. All were able to oxidize Mn(II) and to produce solid dark brown manganese oxides. Shewanella loihica strain PV-4 was the strongest oxidizer, producing oxides at a rate of 20.3 mg/liter/day and oxidizing Mn(II) concentrations of up to 9 mM. In contrast, S. oneidensis MR-1 was the weakest oxidizer tested, producing oxides at 4.4 mg/liter/day and oxidizing up to 4 mM Mn(II). Analysis of products from the strongest oxidizers, i.e., S. loihica PV-4 and Shewanella putrefaciens CN-32, revealed finely grained, nanosize, poorly crystalline oxide particles with identical Mn oxidation states of 3.86. The biogenic manganese oxide products could be subsequently reduced within 2 days by all of the Shewanella strains when culture conditions were made anoxic and an appropriate nutrient (lactate) was added. While Shewanella species were detected previously as part of manganese-oxidizing consortia in natural environments, the current study has clearly shown manganese-reducing Shewanella species bacteria that are able to oxidize manganese in aerobic cultures. IMPORTANCEMembers of the genus Shewanella are well known as dissimilatory manganese-reducing bacteria. This study shows that a number of species from Shewanella are also capable of manganese oxidation under aerobic conditions. Characterization of the products of the two most efficient oxidizers, S. loihica and S. putrefaciens, revealed finely grained, nanosize oxide particles. With a change in culture conditions, the manganese oxide products could be subsequently reduced by the same bacteria. The ability of Shewanella species both to oxidize and to reduce manganese indicates that the genus plays a significant role in the geochemical cycling of manganese. Due to the high affinity of manganese oxides for binding other metals, these bacteria may also contribute to the immobilization and release of other metals in the environment.

From the Surface to the Deep-Sea: Bacterial Distributions across Polymetallic Nodule Fields in the Clarion-Clipperton Zone of the Pacific Ocean

“…Relatives of these Gammaproteobacteria, such as Pseudomonas putida GB-1, contain two multicopper oxidases and thus have the potential to oxidize both Mn(II) and Mn(III) (Geszvain et al, 2013 ). In addition, various Shewanella strains closely related to OTUs found in the present study can reduce Mn under low O 2 conditions, where oxidized Mn is used as a terminal electron acceptor, and therefore have the functional capacity for cycling Mn (Wright et al, 2016 ). Collectively, genetic repertoires catalyzing oxidation-reduction reactions involving Mn-cycling may allow specific gammaproteobacterial OTUs to be successful in the polymetallic-nodule habitat.…”

Uniform and Pitting Corrosion of Carbon Steel by Shewanella oneidensis MR-1 under Nitrate-Reducing Conditions

“…While it is not known if S. oneidensis can oxidize Fe(II) under nitrate-reducing conditions, Shewanella spp. may oxidize Mn(II) under aerobic conditions (49). As such, R2 might be facilitated by nitrate-dependent Fe(II) oxidation by S. oneidensis.…”

Bacterial DNA Extraction Using Individual Enzymes and Phenol/Chloroform Separation

“…Many of these organisms, particularly bacteria, can be pathogenic and are often the causative agent of disease in both humans and other animals ( 1 ). Others play a pivotal role in the cycling of both organic and inorganic material within the environment, which in turn plays a significant role in the bioavailability of nutrients to higher-order organisms ( 2 ). Furthermore, bacterial communities play an essential role in human digestion through the breakdown of sugars and complex carbohydrates, with microbes outnumbering human cells by a factor of ten to one ( 3 ).…”