Global changes: Bacterial populations, environmental pressures and the future of predicting antimicrobial resistance and pathogenicity

Robert Koch quickly recognised that there was no universal environmental condition which would support the growth of all bacteria. Bacterial cells within clonal populations can show phenotypic variation due to internal stochastic processes. Variation between individual cells can be beneficial as well as detrimental to the survival of a population exposed to stress such as change in environmental conditions and many other variables such as selective antibiotic pressure. Variation in the level of proteins relevant for growth or survival among individual cells in a population is likely to play a role in drug resistance and disease. Cells reproduce by incorporating metabolite molecules and die at rates dependent on their gene expression and environmental states.