Application of the ³H-Leucine incorporation technique for quantifying rates of bacterial secondary production associated with decaying wetland plant litter

The 3H-leucine incorporation technique for quantifying rates of bacterial production has increased in popularity since its original description for bacterioplankton communities. Previous studies examining 3H-leucine-incorporation conditions for bacterial communities in other habitats have reported a wide range of final leucine concentrations to achieve saturation-level uptake. This study assessed the application of the 3H-leucine-incorporation procedure for measuring bacterial production associated with decaying wetland plant litter. Substrate saturation experiments were conducted on three dates for bacteria colonizing decaying litter of Typha angustifolia, Schoenoplectus validus, and Phragmites australis. Incorporation of 3H-leucine into protein exhibited a biphasic saturation curve, with lower apparent Km values ranging from 400 nM to 4.2 μM. Upper apparent Km values ranged from 1.3 to 21.7 μM. These results suggest differential uptake by litter-associated microorganisms, with lower Km values possibly representing bacterial uptake and higher Km values representing a combination of both bacterial and nonbacterial uptake