At low osmotic potentials, water molecules move into cells which may cause expansion and rupturing. At high osmotic potentials, water moves out of cells and results in dehydration and shriveling. Organisms are somewhat protected from osmotic shock by their rigid cell walls and some generate intracellular chemicals for osmotic balance. Soil organisms live in environment of constantly changing osmotic pressure even in non-saline soils because of change in soil moisture content. Range of fluctuation more narrower in the subsurface.
Variations are diurnal and seasonal.
Microbes vary widely in regard to ability to initiate growth over certain range of temperature. Cardinal temperatures for given organism or microbial process can be defined General shape of temperature response curve similar for most organisms. Most soil organisms are adapted to survival over wide range of temperature and can survive low temps. Soil acidity is natural or comes from acid rain, heavy use of fertilizers. At charged surfaces may be much more acidic than adjacent solution.