Categories: All - radiation - temperature - ph - solute

by Nuraisyah Talib 9 years ago

245

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.

distribution of microorganism

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