Chapter 11 - Physiological Methods

Abstract

Measurement of microbial activity can provide an indication of the general health of the environment and can be used to evaluate the impact of a disturbance on the microbial community. This chapter describes various types of microbial activity measurements in both pure culture and environmental samples. Activity measurements in pure culture include measurement of substrate utilization, terminal electron acceptor (TEA) utilization, cell mass increase, and carbon dioxide evolution. Utilization of aromatic compounds such as benzene can be measured by the UV spectrophotometer; while, high-performance liquid chromatograph (HPLC) is used for both qualitative and quantitative estimation of a wide variety of compounds such as sugars. The primary activity of the microbial community in undisturbed environments is carbon respiration, and measurement of carbon respiration can be used for the determination of basal rate of microbial activity in soil samples, microbial biomass determination, and biological oxygen demand (BOD). Radiolabelled tracers can be incorporated into the cellular macromolecules—such as proteins or nucleic acids—to monitor the increase in biomass of a bacterial population. The advent of new approaches including functional genomics and proteomics such as microarrays, two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), and matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF-MS) allows investigation of environmental microbial physiology from a much more holistic perspective.