Natural and genetically engineered aerobic bacteria are being evaluated for their potential of forming protective biofilms on the types of alloys used in power plant service water and fire protection systems. In the laboratory, some strains have given rise to large decreases in the corrosion rates of such alloys suggesting that these aerobic bacteria have the potential of significantly extending component lifetime. The use of protective microbes in closed-loop systems may also greatly reduce the need for corrosion inhibitors and biocides, not only in power plants, but also in refineries, and other industrial plants. Such reductions could potentially save the USA billions of dollars annually and eliminate the impact of these chemicals on the environment. Field tests have been initiated to determine the viability and effectiveness of these strains in industrial settings. The laboratory development and preliminary field testing of these bacteria are described.