9614005 SHAPIRO In the relationship between phytoplankton and their associated bacteria, it is assumed that the bacteria derive nutrition from phytoplankton exudates, and that phytoplankton utilize the bacteria as a source of specific vitamins, a source of N or P, or as an alternate carbon source. This SGER project hypothesizes that a major role of this association relates to metal reduction and acquisition. Thus, the phycosphere will be examined as a symbiotic zone of active metal reduction by bacteria and uptake by phytoplankton. As a first step in examining this hypothesis, the researchers will determine whether there are replicable assemblages of bacteria living in close association with phytoplankters, and whether these associations are capable of metal reduction. During this SGER project phytoplankton clones from the Oregon coast will be established and will subsequently be tested with 16s rRNA probe analysis for common marine bacterial genera, including Shewanella putrefaciens, a common metal-reducing species. Population analysis of bacteria associated with phytoplankton natural samples, using DNA amplification, will permit the researchers to characterize bacteria associated with phytoplankton whether or not they are amenable to culturing techniques. Natural samples will be probed with 16s rRNA probes generated from the amplified DNA. The significance of this research lies in its potential to provide a mechanism, based on symbiosis, for metal uptake by phytoplankton. This may prove critical in understanding those regions of the world's oceans where metal limitation of primary production is strongly suggested. ***
