9407776 Tebo Bacteria are known to be important agents in the transformations of metals in the environment, however, in most cases the biochemical mechanisms by which metals are transformed are poorly understood. This proposal focuses on the bacterial oxidation of manganese (Mn) to particulate Mn(III,IV) oxides, mineral phases that adsorb many other metals and which are strong oxidants capable of oxidizing a number of toxic xenobiotic, aromatic, and other organic compounds and hydrogen sulfide. Bacillus strain SG-1 is a marine bacterium whose spores bind and oxidize Mn. SG-1 spores also bind other heavy metals such as cadmium, zinc and cobalt, the latter of which it also oxidizes. Because SG-1 is active over a side range of conditions of low and high ionic strength (freshwater and seawater), pH, temperature, and Mn concentration ( mM) it may also have useful application for a variety of different technologies involving metal precipitation, immobilization and recovery. Thus, this organism is a good model system both for understanding the mechanisms of the biogeochemical cycling of metals in the environment and for studying the potential biotechnological applications of metal precipitation by bacteria. In our previous research with SG-1 we have developed a genetic system and have evidence that Mn(II) oxidation is catalyzed by a spore coat protein. We propose to further characterize the genes involved in Mn oxidation, to isolate the active Mn oxidizing protein and characterize its metal binding and oxidizing properties, and to determine whether the Mn oxidation (mnx) genes we have identified in SG-1 have homologs in other Bacillus species or environmental Mn oxidizing isolates. The fundamental knowledge resulting from these studies may ultimately form the basis for technologies for environmental remediation and metal recovery and recycling. %%% Metal pollution is frequently a problem in the environment. unlike many other kinds of toxic substances, metals ca nnot be destroyed, only transformed from one form to another. For most metals, certain forms are toxic while others are either non-toxic or less toxic. In most cases, it is the dissolved forms of metals that are toxic whereas their solid forms are not. Bacteria transform metals between their various forms. In some cases these are very general mechanisms not specific to particular metals. In other cases they are highly specific. It is important to study the mechanisms bacteria use to transform metals to understand the behavior of metals in the environment and ultimately employ bacteria for clean up of metal pollution or recovery of valuable metals. This proposal focuses on an organism that transforms dissolved metals to solid forms. It is a marine bacterium that forms spores which are dormant seed-like structures. The spores do the metal transformations and accumulate metals on their cell surfaces. Because the spores are resistant to many kinds of damage they can capture metals from water under a wide range of conditions making them suitable for environmental applications. In previous work we have cloned some of the genes involved in metal capture. It appears that a protein on the surface of the spores is responsible. Such proteins could be genetically engineered for specific purposes. The goal of this research is to isolate and study this protein and to learn whether such protein are found in other bacteria that transform metals. ***
