Thymidine Incorporation by the Microbial Community of Standing Dead Spartina alterniflora

Thymidine incorporation by the microbial community on standing dead leaves of Spartina alterniflora did not obey many of the assumptions inherent in the use of the technique in planktonic systems. Incorporation rates of [methly-H]thymidine were nonsaturable over a wide concentration range (10 to 10 nM). Owing to metabolism by both fungi and bacteria, a major fraction of the radiolabel (mean, 48%) appeared in protein. Extraction of the radiolabeled macromolecules was inefficient, averaging 8.8%. Based on an empirically derived conversion factor, 4 x 10 cells . mol of thymidine, doubling times ranged from 4 to 69 h for the epiphytic bacterial assemblage.