BIOL2142 Lecture 5: Environmental Factors and Microbial Growth
Document Summary
Most organisms grow in fairly moderate environmental conditions. Grow under harsh conditions that would kill most other organisms. Reduce osmotic concentration of cytoplasm in hypotonic solution mechanosensitive (ms) channels in plasma membrane allow solutes to leave. Increase internal solute concentration with compatible solutes to increase their internal osmotic concentration in hypertonic solutions solutes compatible with metabolism and growth (kcl and organic solutes such as choline, proline and glutamic acid) Maintains solute concentration slightly higher than that in the external environment. Grow optimally in the presence of nacl or other salts at a concentration above about 0. 2m. Require salt concentrations of 2m and 6. 2m (almost saturation point) Cell wall, proteins and plasma membrane require high salt to maintain stability and activity. Solutes and water activity (aw) - water activity ph . Reduced by interaction with solute molecules - osmotic effect. Also equal ratio of solutions vapour pressure (psoln) to that of pure water (pwater) aw = psoln/pwater.
