FIG. 3.

Examples of microautoradiograms of [³⁵S]DMSP-labeled (A) and [³H]Leu-labeled (B) bacteria observed under transmitted light (for exposed silver grains) and epifluorescence microscopy (for DAPI stain). White arrows point to DAPI-stained nonradiolabeled cells, while black arrows point to DAPI-stained radiolabeled cells. Note morphological diversity of labeled cells and low background of exposed silver grains compared to labeled cells. The [³⁵S]DMSP and [³H]Leu microautoradiograms are from a nutrient-enriched sample on days 2 and 8 of the DIME (Gulf of Mexico, June 2000).