ABSTRACT
Brock and Brock introduced microautoradiography (MA) as a tool for the study of activities by individual aquatic microorganisms from natural samples. The technique has subsequently been used to address a variety of ecological questions regarding bacterial activities in natural aquatic systems. MA is also useful for determining labeling specificity, that is, whether targeted microorganisms take up labeled substrates at the exclusion of nontargel microorganisms. Microautoradiography is performed on microbes that have been concentrated on membrane filters. Briefly, slides are coated with emulsion and the filter is placed face down on the liquid emulsion. The emulsion is then hardened by cooling and drying. Cells and developed silver grains can then be detected with fluorescence and bright-field microscopy. Autoradiographs are examined using a combination of epifluorescence and bright-field illumination. Bright-field illumination can be used to scan autoradiographs for clusters of silver grains, while epifluorescence illumination is used to verify that the cluster of silver grains is associated with a microbial cell.
