factors affecting growth of microorganism

1. PHYSICAL FACTORS
THE GROWTH OF
MICRORGANISM
Guided by: Presented by:
Dr.Monika sogani Raj & Sakshi sharma
Associate professor Bsc biotecnology
Manipal university jaipur iv semester

2.  An orderly increase in the quantity of all the
cellular constituents.
 The growth of microorganisms is influenced by
various physical and chemical factor of their
environment.
 Physical factor- temperature,pH ,osmotic
pressure, hydrostatic pressure, and radiation
 Chemical factors- oxyegen,
carbon,nitrogen,phosphorus,sulfur,etc.

3. Temperature
pH
Osmotic pressure
Hydrostatic pressure
Radiation
pressure

4.  Temperature is the most important factor that
determines the rate of growth, multiplication, survival,
and death of all living organisms.
 High temperatures damages microbes by denaturing
enzymes,transport carriers and other proteins.
 Microbial membranes are disrupted by temperatures
extremes.
 At very low temperature membranes also solidify and
enzymes also do not fuction properly

5. Minimum growth temperature
Optimum growth temperature
Maximum growth temperature

6.  The lowest at which organism grow is the minimum growth
temperature.
 The temp at which the most rapid rate of multiplication
growth.
 The highest at which growth occurs.
A temperature only slightly above this point frequently kills the
microorganisms by inactivating critical enzyme s

7. Growth rate v/s temperature

8. Classification of bacteria
according to growth temperature

9. 1. The term cryophiles was first used by S.Schmidth-
Nelson.
2. Extremeophilic organism that are capable of
growth and reproduction in cold temperatures.
3. Temperature range:-20 ̊CTO +10 ̊C.
4. Examples: Oscillatoria, chlamydomnas
nivalis,methanogenium, etc.

10. 1. Grows best in moderate temperature.
2. Temperature range: 20 ̊C to 45 ̊C.
3. Example: Escherichia coli ,strptococcus
phneumonia, etc

11. 1. Have optimal and maximal growth temperatures
above 15 and 20 ̊C respectively.
2. Pyschrotrophic bacteria and funji are the principal
cause of spoilage of refrigerated food.
3. Example: pseudomonas ,Aeromonas, Bacillus,
Clostridium etc.
4. Cold tolerant bacteria.

12. 1. Derived from greek word thermotita
meaning heat and philia meaning love.
2. Heat loving ,microorganism.
3. Grow at 50 ̊C or higher.Their growth
minimum is usually around 45 ̊C amd often
optima between 50 to 80 ̊C.
4. Examples:Thermus aquaticus,Geogemma
barassil,etc.

13. 1. Thrives in extremely hot environments.
2. Temperature range: 80 C to 113 C.
3. First discovered byThomas d.Brock in 1965, in
hot springs in yellowstone national park.
4. The cell membranes contain high levels of
saturated fatty acids to retain its shape at high
temperatures.
5. Examples : Sulfolobus , Methanococcus
jannaschii ,thrmotogo, etc

14. 1. pH refers to negative logarithm of hydrogen
ion concentration.
2. Microbial growth is strongly affected by the
pH of the medium
3. Drastic variations in cytoplasmic pH disrupt
the plasma membrane or inhinit the activity
of enzymes and membranes transport
proteins.

17. What about microbes that live at pH extremes?
 Drastic variations in cytoplasmic pH can harm microorganisms by
disrupting the plasma membrane or inhibiting the activity of enzymes
and membrane transport proteins. Most microbes die if the internal pH
drops much below 5.0 to 5.5. Changes in the external pH also can alter
the ionization of nutrient molecules and thus reduce their availability to
the organism.
 Extreme alkaliphiles such as Bacillus alcalophilus maintain their
internal pH dose to neutrality by exchanging internal sodium ions for
external protons.
 Acidophiles use a variety of measures to maintain a neutral internal pH.
These include the transport of cations (e.g., potassium ions) into the
cell, thus decreasing the movement of H+ into the cell; proton
transporters that pump H+ out if they get in; and highly impermeable
cell membranes.

18.  The importance of oxygen to the growth of an organism
correlates with the, processes it uses to conserve energy.
 Almost all energy-conserving metabolic processes involve
the movement of electrons through a series of membrane-
associated electron carriers called an electron transport
chain (ETC).
 . Oxygen serves as the terminal electron acceptor for the
ETC in the metabolic process called aerobic respiration. In
addition, aerobic eukaryotes employ Oz in the synthesis of
sterols and unsaturated fatty acids.
 Facultative anaerobes do not require Oz for growth but
grow better in its presence. In the presence of oxygen, they
use O2 as the terminal electron acceptor during aerobic
respiration.

19. The different relationships with 02 are due to
several factors, including the inactivation of
proteins and the effect of toxic O2 derivatives.
Enzymes can be inactivated when sensitive
groups such as sulfhydryls are oxidized.
Toxic O2 derivatives are formed when cellular
proteins such as flavoproteins transfer
electrons to 02•
These toxic O2 derivatives are called reactive
oxygen species (ROS), and they can damage
proteins, lipids, and nucleic acids. ROS include
the superoxide radical, hydrogen peroxide, and
the most dangerous hydroxyl radical.


21.  Organisms that spend their lives on land or the
surface of water are always subjected to a
pressure of 1 atmosphere (atm; 1 atm is -0.1
megapascal, or MPa for short) and are never
affected significantly by pressure.Other
organisms, including many bacteria and
archaea, live in the deep sea (ocean depths of
1,000 m or more), where the hydrostatic
pressure can reach 600 to 1,100 atm and the
temperature is about 2 to 3°C.These high
hydrostatic pressures affect membrane fluidity
and membrane-associated function.

22.  Ultraviolet (UV) radiation can kill microorganisms due to its
short wavelength (approximately from 10 to 400 nm) and
high energy.
 The most lethal UV radiation has a wavelength of 260 nm,
the wavelength most effectively absorbed by and
damaging to DNA.
 Longer wavelengths of UV light (near-UV radiation; 325 to
400 nm) can also harm microorganisms because they
induce the breakdown of the amino acid tryptophan to
toxic photoproducts.These toxic photoproducts plus the
near-UV radiation itself produce breaks in DNA strands.
 Even visible light, when present in sufficient intensity, can
damage or kill microbial cells. Usually pigments called
photosensitizers and 02 are involved

23.  A selectively permeable plasma membrane separates
microorganisms from their environment, they can be
affected by changes in the osmotic concentration of their
surroundings.
 If a microorganism is placed in a hypotonic solution (one
with a lower osmotic concentration), water will enter the
cell and cause it to burst unless something is done to
prevent the influx of water or inhibit plasma membrane
expansion.
 Conversely, if it is placed in a hypertonic solution (one
with a higher osmotic concentration), water will flow out
of the cell. In microbes that have cell walls, the
membrane shrinks away from the cell wall-a process
called plasmolysis.

24. . These osmophiles include Some microbes
are adapted to extreme hypertonic
environments halophiles, which require
the presence of NaCl at a concentration
above about 0.2 M.
The first approach used by halophiles is to
maintain high levels of inorganic compatible
solutes such as potassium chloride (KCl) in the
cytoplasm. The second approach is to increase
the internal osmotic concentration with organic
compatible solutes such as choline, betaine, and
amino acids such as proline and glutamic acid

25.  http://www.nptel.ac.in
 Prescotts in microbiology

26. Thank you