This material was originally published in the Purdue Cytometry CD-ROM Series . Flow Cytometry and Microbiology A flow cytometric study of stationary phase gene expression in E.coli using lacZ reporter gene fusion. Thus information on the heterogeneity of cells within a culture can be obtained. The population with the largest fluorescence contained the smaller cells, demonstrating that a decrease in cell size, which indicates the onset of stationary phase, was accompanied by an increase in expression of rpoS. Introduction Growth can be defined as the orderly increase of all chemical components. In a medium to which they have become fully adapted, bacteria are in a state of balanced growth, during which an increase in biomass is accompanied by a comparable increase of all other measurable properties of the population, e.g., protein, DNA, RNA etc.
Batch growth is carried out in a finite volume of nutrients and is characterised by four phases.
Lag phase occurs directly after inoculation during which time the cells undergo a change in chemical composition before they are capable of growth. Exponential phase is a time of maximum growth where cell number increases exponentially. Bacteria held in a nongrowing state eventually die, from depletion of cellular energy amongst other things, the death phase is a linear decrease in number of viable cells with time. The transition between exponential and stationary phases involve unbalanced growth as the cells change their chemical composition, physiology and genetic status. Schematic diagram showing growth of E.coli in batch culture portraying the various growth phases and the point of rpoS induction.