Measurements of Heme Levels and Respiration Rate in Salmonella enterica Serovar Typhimurium

This chapter describes assays for the measurement of heme levels and the rate of respiration in bacteria. An assay of ALA supplementation is described, in which the effect of exogenous ALA in reversing sensitivity to hydrogen peroxide is an indication of a reduced flow through the heme biosynthesis pathway. A protocol for measurement of the relative amount of heme by a fluorescence assay, based on stripping the iron from the heme moiety, leaving a protoporphyrin molecule which fluoresces following excitation at 400 nm, is also provided. Finally, a method for the measurement of respiration (oxygen consumption) rate is provided. In this method, the respiration of the cell population is expressed as the specific respiration rate during one doubling time of the population.