Multiparameter flow cytometry of bacteria.

The small size of bacteria makes some microbial constituents undetectable or measurable with only limited precision by flow cytometry. Bacteria may also behave differently from eukaryotes in terms of their interaction with dyes, drugs, and other reagents. It is therefore difficult to design multiparameter staining protocols that work, unmodified, across a wide range of bacterial species. This chapter describes reliable flow cytometric methods for assessment of the physiologic states of Gram-negative organisms, on the one hand, and Gram-positive organisms, on the other, based on measurement of membrane potential and membrane permeability. These techniques are useful in the assessment of effects of environmental conditions and antimicrobial agents on microorganisms.