Microbial processing of lead in the environment is poorly understood. Studies of prokaryotic tolerance and resistance to soluble lead have revealed two general mechanisms. The first of these is an active efflux mechanism, a frequent heavy metal resistance strategy. The second mechanism appears to be precipitation of the lead to an insoluble form, previously identified by the PI to be Pb9(PO4)6. The primary objectives of this project are: (1) to generate collections of transposon-induced lead hyper-precipitator and non-precipitator mutants of the freshwater bacterium Caulobacter crescentus; (2) to use the inserted transposon sequences to amplify segments of the disrupted genes via PCR techniques; (3) to determine the identity of the disrupted genes via sequence analysis of the resulting PCR products; and (4) to develop a defined medium that will permit a better understanding of the medium conditions required for Pb9(PO4)6 precipitation. The results collected from these analyses will be used to develop a model describing the generation and regulation of Pb9(PO4)6 precipitation. Long-term implications of the study include a greater understanding of heavy metal resistance and possibly the development of lead bioremediation procedures. The research environment established by this project will integrate student participation into both the execution of the research and the dissemination of the project's results. Furthermore, this study has a strong potential to create new interdisciplinary projects involving engineering undergraduates -- particularly in the areas of chemical and environmental engineering -- in both the research laboratory and the classroom.
