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Chapter 34 : Bacterial Secondary Productivity
Planktonic heterotrophic bacteria (bacterioplankton) are now recognized to be a large and metabolically active group that contributes significantly to the biomass and to the flow of carbon in aquatic systems. Various methods available to determine bacterial biomass production (BBP), those that employ radiolabeled precursors to estimate the rate of synthesis of nucleic acids and proteins have become the most widely used and are the focus of this chapter. In this chapter, the rationale, advantages, and disadvantages of the most commonly used methods based on the incorporation of thymidine (TdR) and leucine (Leu) methods are discussed. In addition, methods to determine empirically a conversion factor from thymidine or leucine incorporation to cells produced is presented as well as several procedures designed to test various assumptions of these methods. Alternative methods to determine BBP that do not rely on the uptake of radiolabeled compounds are also discussed in the chapter. The BBP measurement methods presented in this chapter estimate the total BBP and do not provide information on the relationship between bacterial diversity and metabolism. The chapter concludes with a review of novel methods that combine measurements of BBP with microscopy and molecular techniques to determine the proportion of total bacteria that are active, and the contribution to total BBP of specific phylogenetic groups.