80 C Psychrophiles open ocean water is between 1 and 3 C. Artic and Antartic regions are cold. Adaptation membranes rich in unsaturated fatty acids Thermophiles hot springs all over the world fermenting compost Adaption thermostable proteins with usually a few changes in the amino acid sequence when compared to a mesophile's protein saturated fatty acids in their membranes Acidity and alkalinity Most environments are between 5 and 9 and optima are between these values, around neutral pH of 7. Acidophiles live at low pH Obligate acidophiles such as Thiobacillus. Important to biotechnology since they have hydolytic proteases that function at alkaline pH and are used in household cleaners. Water availability - bacteria need water as a solvent.
Water availability is expressed as water activity - how much water is available.
Water moves from high water activity values to lower values in the process of osmosis . Different bacteria have different tolerances towards low water activities. In fact, preservation process takes advantage of lower water activity which causes plasmolysis or pulling away of the membrane from the cell wall. This inhibits cell growth. Oxygen - 1.