This thesis examines the taxonomy of, and manganese (II) oxidation by, a supposed species of bacteria known as "Pseudomonas manganoxidans", originally described in the 1970's by Schweisfurth and colleagues. It is shown here that "P. manganoxidans" is more properly considered a member of the common soil and water species Pseudomonas putida. Another manganese-oxidizing species of doubtful taxonomic validity, "Arthrobacter siderocapsulatus", is also shown to be P. putida. Furthermore, it appears that manganese oxidation is a common property of other members of P. putida, not before known to be metal-oxidizers. Some related strains of Pseudomonas were also shown to have the ability to oxidize manganese. Contrary to previous reports, cell-free manganese oxidation in "P. manganoxidans" requires the participation of oxygen, and can be considered enzymatic. The activity is induced by carbon starvation much more than by starvation for ammonium or for phosphate. Heat shock and peroxide shock were not seen to induce manganese oxidation activity, as they do for some other starvation-stress activities. The detailed mechanism of and the purpose for manganese oxidation in this species remain unknown. Pseudomonas putida, as a species well-studied biochemically and genetically, should be useful as a model system for studying a mechanism of bacterial manganese oxidation.