Practice 21 - Osmotic pressure and pH effects on microorganisms

Abstract

The growth of microorganisms is affected by the amount of water and hydrogen ions present in their environment. The amount of water entering or leaving the cell depends on the amount of water present in the environment. There are three osmotic solutions depending on water content of environment: isotonic, hypotonic, and hypertonic. The concentration of hydrogen ions, which is designated by the term pH, limits the growth of microorganisms. There is a minimum, optimum, and maximum growth pH for microorganisms. The microorganisms show best growth rate at the optimum pH. The growth rate of microorganisms can be measured in terms of colony-forming unit (cfu) per mL. In this practice, the effects of osmotic pressure and pH on the growth of microorganisms are evaluated.