Effects of Bacterial Manganese Oxidation on Intracellular Manganese
Authors:Vu Ha, Brenda Hall, Sophia Hernandez, Allison Nguyen
Mentor:Hope Johnson, Associate Professor of Biology, California State University Fullerton
Bacteria can oxidize manganese (Mn) (II) to manganese Mn(III or IV) oxides, but little is known as to why they are able to do this. An understanding of why these bacteria oxidize Mn(II) may contribute significantly to advances in bioremediation. Mn oxidizing bacteria can play a role in bioremediation because the Mn oxides they produce can oxidize and sequester heavy metals. Erythrobacter sp. SD-21, a marine alpha-proteobacteria, and Pseudomonas putida sp. GB-1, a freshwater gamma proteobacteria, both oxidize Mn(II) to Mn(III or IV). Research performed in our laboratory suggests that Mn(II) oxidation causes an increase in the bacteria’s intracellular concentration of Mn. For this reason, we determined whether the intracellular Mn that accumulates when P. putida GB-1 and Erythrobacter sp. SD-21 oxidizes Mn is associated with the protein or small molecules in the cell. We found that the intracellular Mn was largely associated with the <3k fraction (small molecule fraction) in both Erythrobacter sp. SD-21 and P. putida GB-1. High intracellular Mn has been shown to protect cells from oxidative stress. Protein carbonylation, an indicator of oxidative stress, was determined and compared between cells grown in the presence and absence of Mn(II) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting. Higher intracellular Mn did not reduce protein carbonylation thus not protecting the proteins during oxidative stress.