Iron reduction is an important ecological process in marine environments since availability can be a limiting factor in both the primary productivity of surface waters and the remineralization of organic matter in bottom sediments. The primary objective of this project is to use molecular probes to study the microbial ecology of iron-reducing bacteria in anaerobic marine environments. Ferri-reductase antibody probes, ferri-reductase structural gene probes and genera-specific rRNA probes will be constructed and used to determine: (1) the distribution and (2) the environmental parameters which control expression of iron reduction genes and enzymes in those environments. In order to construct the ferri-reductase molecular probes, the project will initially focus on understanding the process of microbial iron reduction. Shewanella putrefaciens will be used as a model iron-reducing marine organism, selected largely because it is commonly isolated from a variety of marine sources, and because of its unique metabolic versatility: S. putrefaciens is capable of coupling the oxidation of an extensive array of organic compounds to the reduction of many of the respiratory electron acceptors found in marine environments including O2, NO3-, NO2-, MnO2, SO32- and Fe(III). Preliminary molecular work has centered on the isolation and characterization of mutant strains deficient in iron reduction capability. The project will use complimentary genetic and biochemical techniques to clone and characterize the genes and gene products involved in expression of a functional ferri-reductase. Ferri-reductase antibody probes and ferri- reductase structural gene probes will be constructed and used in ecological studies to detect the presence of iron-reducing bacteria in marine waters and sediments, and to determine which environmental parameters control expression of iron reduction genes and enzymes in those environments. Results from the project will provide details on the molecular biology and ecology of microbially-mediated iron reduction in the marine environment.//
