The application of micro-autoradiographic techniques to ecological studies

Abstract

Microscopy and radioactive isotopes, common tools of the limnologist, have been combined with photography to enable us to detect radioactivity at the cellular level, with a considerable increase in the amount of information that can be gained from a single experiment. Except for a darkroom, safelight and water bath, no specialized equipment is required. Autoradiography can be not only a useful adjunct to other radioactivity experiments but it can also be used as a sole method to study nutrition and physiology in the laboratory as well as in the natural environment. Simple biochemical extraction methods are presented, and autoradiographic results obtained from experiments based on these methods are used as an example to show how the autoradiograms can be analyzed and to demonstrate the validity of the autoradiographic techniques. Detailed information describes how autoradiography can be used to evaluate the mode and rate of growth of bacteria. Methods for the preparation of specimens, handling of liquid autoradiographic emulsion, and developing the autoradiograms are presented in considerable detail; some of these techniques have been adapted in our own laboratory to meet the needs of the limnologist. Particular attention has been paid to the precautions which should be taken to insure successful use of these techniques. Photomicrographs of auto-radiographs of various organisms from different habitats illustrate the results obtained.