13] Fluorescent probes applied to physiological characterization of bacterial biofilms

Abstract

Progress in the development of in situ , intracellular fluorescent labels and probes has facilitated the rapid assessment of microbial physiology without cultivation. Labels most often have inherent fluorescence regardless of their being flee, nonspecifically bound, or bound to their cellular target. The probes most applicable to biofilm systems are those that remain nonfluorescent until acted on by the cellular target. The advantages of using these types of labels and probes include the direct, single cell assessment of (1) physiological status, (2) specific metabolic activities, (3) gene expression, and (4) total cell densities. Biofilm composition heterogeneity is influenced directly by constituents from the overlying bulk phase adsorbing or precipitating onto and into the biofilm matrix and intrabiofilm deposition of microbially secreted products. Individually or collectively, these constituents may influence the performance of a label or probe. This chapter provides a list of characteristics that should be considered when choosing a label or probe. It also provides some insights into the complexities of selecting an appropriate label or probe for investigating the microbial physiology of biofilm systems.