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Categorii: Tot - radiation - temperature - ph - solute

realizată de Nuraisyah Talib 10 ani în urmă

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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