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PHYSICAL FACTORS
INFLUENCING THE GROWTH OF
MICROORGANISMS
Guided by:
Dr. Ruchi Seth
Assistant Professor - I
Department of ...
Growth
 An orderly increase in the quantity of all the cellular
constituents.
 The growth of microorganisms is influence...
Physicalfactorsinfluencingthegrowthofmicroorganisms
Temperature pH
Osmotic
Pressure
Hydrostatic
Pressure
Radiation
Temperature
 Temperature is the most important factor that
determines the rate of growth, multiplication,
survival, and d...
Types of temperature
Minimum growth temperature
Optimum growth temperature
Maximum growth temperature
1. Minimum growth temperature
The lowest temperature at which organisms grow is
the minimum growth temperature.
2. Optimum...
Classification of bacteria according to
growth temperature
 Psychrophiles/cryophiles-
1. The term psychrophile was first used by S.
Schmidt-Nelson.
2. Extremophilic organisms that ...
 Mesophiles-
1. Grows best in moderate temperature.
2. Temperature range: 20°C to 45°C.
3. Examples: Escherichia coli, St...
 Psychrotrophs-
1. Cold‐tolerant bacteria.
2. Have optimal and maximal growth temperatures
above 15 and 20°C, respectivel...
 Thermophiles-
1. Derived from Greek word thermotita meaning
heat and philia meaning love.
2. Heat-loving microorganisms....
 Hyperthermophiles-
1. Thrives in extremely hot environments.
2. Temperature range: 80°C to 113°C.
3. First discovered by...
 pH refers to negative logarithm of hydrogen ion
concentration.
 Microbial growth is strongly affected by the pH of the
...
Classification of bacteria according to pH
 Acidophiles- Grow between pH 0 and 5.5.
Examples: Ferroplasma, Thiobacillus thioxidans, Sulfolobus
acidocaldarius, etc.
...
Osmoticpressure(solutesandwateractivity)
 Osmotic pressure is the minimum pressure which
needs to be applied to a solutio...
Classification of bacteria according
to osmotic pressure
1. Osmotolerant are those microorganisms which can
grow at relati...
HydrostaticPressure
 Force acting per unit area.
Classification of bacteria on the basis
of hydrostatic pressure
 Baroto...
Radiation
 Sunlight-The major source.
 Infrared is the major source of Earth’s heat.
 Ionising rays can produce mutatio...
References
 Microbiology, P.D. Sharma
 www.slideshare.net
 General Microbiology, C.P Powar
Factors affecting the growth of microbes
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Factors affecting the growth of microbes

Microbiology

Factors affecting the growth of microbes

  1. 1. PHYSICAL FACTORS INFLUENCING THE GROWTH OF MICROORGANISMS Guided by: Dr. Ruchi Seth Assistant Professor - I Department of Biotechnology Presented By : Prachi Gupta B.Sc. Biotechnology I-Semester
  2. 2. Growth  An orderly increase in the quantity of all the cellular constituents.  The growth of microorganisms is influenced by various physical and chemical factors of their environment.  Physical factors- Temperature, pH, osmotic pressure, hydrostatic pressure and radiation.  Chemical factors- Oxygen, carbon, nitrogen, phosphorus, sulfur, etc.
  3. 3. Physicalfactorsinfluencingthegrowthofmicroorganisms Temperature pH Osmotic Pressure Hydrostatic Pressure Radiation
  4. 4. Temperature  Temperature is the most important factor that determines the rate of growth, multiplication, survival, and death of all living organisms.  High temperatures damage microbes by denaturing enzymes, transport carriers, and other proteins.  Microbial membrane are disrupted by temperature extremes.  At very low temperatures membranes also solidify and enzymes also do not function properly.
  5. 5. Types of temperature Minimum growth temperature Optimum growth temperature Maximum growth temperature
  6. 6. 1. Minimum growth temperature The lowest temperature at which organisms grow is the minimum growth temperature. 2. Optimum growth temperature The temperature at which the most rapid rate of multiplication occurs. 3. Maximum growth temperature The highest temperature at which growth occurs. A temperature only slightly above this point frequently kills the microorganisms by inactivating critical enzymes.
  7. 7. Classification of bacteria according to growth temperature
  8. 8.  Psychrophiles/cryophiles- 1. The term psychrophile was first used by S. Schmidt-Nelson. 2. Extremophilic organisms that are capable of growth and reproduction in cold temperatures 3. Temperature range: −20°C to +10°C. 4. Examples: Oscillatoria, Chlamydomonas nivalis, Methanogenium, etc.
  9. 9.  Mesophiles- 1. Grows best in moderate temperature. 2. Temperature range: 20°C to 45°C. 3. Examples: Escherichia coli, Streptococcus pneumoniae, etc.
  10. 10.  Psychrotrophs- 1. Cold‐tolerant bacteria. 2. Have optimal and maximal growth temperatures above 15 and 20°C, respectively. 3. Psychrotrophic bacteria and fungi are the principal cause of spoilage of refrigerated food. 4. Examples: Pseudomonas, Aeromonas, Bacillus, Clostridium, etc.
  11. 11.  Thermophiles- 1. Derived from Greek word thermotita meaning heat and philia meaning love. 2. Heat-loving microorganisms. 3. Grow at 50°C or higher. Their growth minimum is usually around 45°C and often optima between 50 and 80°C. 4. Examples: Thermus aquaticus, Geogemma barossii, etc.
  12. 12.  Hyperthermophiles- 1. Thrives in extremely hot environments. 2. Temperature range: 80°C to 113°C. 3. First discovered by Thomas D. Brock in 1965 , in hot springs inYellowstone National Park, Wyoming. 4. The cell membrane contains high levels of saturated fatty acids to retain its shape at high temperatures 5. Examples: Sulfolobus, Methanococcus jannaschii, Thermotoga, etc.
  13. 13.  pH refers to negative logarithm of hydrogen ion concentration.  Microbial growth is strongly affected by the pH of the medium.  Drastic variations in cytoplasmic pH disrupt the plasma membrane or inhibit the activity of enzymes and membrane transport proteins. pH
  14. 14. Classification of bacteria according to pH
  15. 15.  Acidophiles- Grow between pH 0 and 5.5. Examples: Ferroplasma, Thiobacillus thioxidans, Sulfolobus acidocaldarius, etc.  Alkalophiles- Grow between pH range of 7.5 to 14. Examples:Thermococcus alcaliphilus, etc.  Neutrophiles- Grow between pH 5.5 to 8.0 Examples: Lactobacillus acidophillus, E. coli, Pseudomonas aerunginosa, etc. Bacteria prefer media of pH near neutrality, and usually cannot tolerate pH values much below 4-5.
  16. 16. Osmoticpressure(solutesandwateractivity)  Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a SPM.  Types of solution: 1. Hypotonic 2. Isotonic 3. Hypertonic  Water activity of a solution is 1/100 the relative humidity of the solution. It is equivalent to the ratio of the vapour pressure of solution to that of pure water. Water activity= Vapour pressure of solution Vapour pressure of pure water
  17. 17. Classification of bacteria according to osmotic pressure 1. Osmotolerant are those microorganisms which can grow at relatively high salt concentration. Examples: Aeromonas spp., Staphylococcus spp, etc. 2. Halophiles- Grow in the presence of salt at conc. Above 0.2 to 0.6. Examples: Halobacterium halobium
  18. 18. HydrostaticPressure  Force acting per unit area. Classification of bacteria on the basis of hydrostatic pressure  Barotolerant – Does not get affected by increased pressure.  Barophiles/ Piezophiles- Bacteria which grow at moderately high hydrostatic pressures. Examples: Halomonas salaria, xenophyophores, etc.
  19. 19. Radiation  Sunlight-The major source.  Infrared is the major source of Earth’s heat.  Ionising rays can produce mutations which may result in death.  Visible light is beneficial because it is the source of energy for photosynthesis.
  20. 20. References  Microbiology, P.D. Sharma  www.slideshare.net  General Microbiology, C.P Powar

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