作者：Nuraisyah Talib 9 年以前
256
distribution of microorganism
Microorganisms are influenced by various physical and chemical factors that affect their growth and distribution. One major physical factor is radiation, particularly sunlight, which provides essential UV radiation but can also cause DNA damage.
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Distribution of microorganism Physical factors radiation slight damage of UV is reversible - photoreactivation UV radiation damage :formation of thymine dimers most important criteria : intensity of light wavelenght duration visible light, UV radiation, infrared rays and radio waves major source of radiation :sunlight pressure -barophilic
-piezophilic
-barotolerant
-eztreme barophiles deep sea ->600-1,100 atm -> barotolerant inhibit chemical rxn land or surface of water -> pressure 1 atm temperature 1)psychrophiles ->opt : -5-10°C
2)psychrotrophs ->opt : 20-30°C
3)mesophiles ->opt : 20-45°C
4)thermophiles ->opt : 45-65°C
5)hyperthermophiles ->opt : 90-100°C solute & water activity quantity of water availability=water activity hypertonic solution (high [osmotic]) hypotonic solution(low [osmotic]) Chemical factors trace elements not necessary to specifically provide for function of enzyme or metabolism e.g : Fe, Mn, Mg, Cu, Zn special growth factor e.g. : Legionella pneumophila -specific nutrient eg. amino acid,/vitamin in low concentration
-absence : cannot grow nitrogen, phosphorus & sulfur carbon -chemical building block for cells
-source of energy water for cellular function, metabolism as solvent oxygen concentration aerobes
facultative anaerobes
aerotolerant anaerobes|
strict/obligate anaerobes
microaerophiles pH acidophiles : optima pH 0 to 5.5
neutrophiles : optima pH 5.5 and 8.0
alkalophiles : optima pH 8.5 to 11.5
extreme alkalophiles : optima above pH 10 Growth limitation by
environmental factors Shelford's Law of Tolerance Liebig's Law of the Minimum
