WHEN NUTRIENT LIMITATION PLACES BACTERIA IN THE DOMAINS OF SLOW GROWTH - METABOLIC, MORPHOLOGICAL AND CELL-CYCLE BEHAVIOR

Growth systems appropriate for studying mass transfer in different bacterial environments are reviewed. Fed batch and recycling fermentors are suited to modelling nutrient limitation and slow growth. Use of these two growth systems reveals the existence of three growth rate regions, or domains, defined by maintenance energy demands, nucleotide regulation, metabolism, and physiological behavior. They are exemplified in Escherichia coli by domain-dependent synthesis of attachment antigens, heat-labile toxin, and inducible enzymes. Distribution of the bacterial population among cell cycle stages changes with growth rate domain because lengths of the stages differ in their dependence on growth rate. This produces subpopulations whose ratios vary with growth rate and that are likely to differ in both molecular composition and stress resistance.