Temperature affect all chemical reactions (inorganic. organic or biochemical) (tolerance range -12 °C to >100 °C)
Visible light (320-800 nm) for photosynthesis
Ultraviolet light (1-320nm) causes damage because (1) 260 nm coincides with the absorption maximum of DNA, and (2) the wave length of UV also overlaps with most proteinsí absorption max.
Pressure (atmospheric, hydrostatic & Osmotic)
Pressure, in general, does not have much direct effect on life system, but it can be indirectly affecting water, oxygen, and other resources.
Salinity (salt concentration, mainly affect water availability)
pH and [H+]
pH affects enzymes directly and also influence the dissociation and solubility of many chemicals.
Many enzymatic reactions are oxidation-reduction reactions in which one compound is oxidized and another compound is reduced. The ability of an organism to carry out oxidation-reduction reactions depends on the oxidation-reduction state of the environment, or the Redox potential (Eh)
The redox potential is a relative value measured against the arbitrary 0 point of the normal hydrogen electrode. Any system or environment that accepts electrons from a normal hydrogen electrode is a half-cell that is defined as having a possitive redox potentail; any system donates electrons to this hydrogen electrode is defined as having a negative redox potential. Eh is measured in mV. A high possitive Eh indicates an environment that favors oxidation reaction such as free oxygen. A low negative Eh indicates a strong reducing environment, such as free metals.
So strickly aerobic microorganisms can be active only at positive Eh values, whereas strickly anaerobes can be active only at negative Eh values.
Redox affect the solubility of nutrients especially metal ions.
Oxygen strongly affect redox potential.
Nutrients (Organic and Inorganic)