The physical parameters required for bacterial growth include temperature, pH, and gaseous requirements. Temperature affects bacterial growth rates, with psychrophiles growing at 0-20°C, mesophiles at 25-40°C, and thermophiles at 50-80°C or higher. Bacteria also require specific pH ranges, with acidophiles growing best at pH 0-5.5, neutraphiles at pH 5.5-8, and alkaliphiles at pH 7.5-14. Additionally, bacteria have different oxygen requirements, including aerobic, anaerobic, facultative, aerotolerant, and microaerophilic bacteria. Special cultivation techniques are needed for growing strict anaer

1. Physical parameters required
for growth of bacteria
Dr. Pulipati Sowjanya
Professor & HOD
Dept. of Pharm. Biotechnology
Vignan Pharmacy College
Guntur

2. Temperature
PH
Gaseous Requirement
Physical Parameters

3. The physical factors affects the growth of microorganism.
1) Temperature
Temperature is the most important factor that influences the rate of enzyme catalysed reactions
and rate of growth.
For every organisms there is an optimum temperature for growth and minimum temperature for
inhibiting the growth.
Most extreme the microbes need liquid/ water to grow.
Some algae and fungi grow at 55-600C.
Prokaryotes are grow at 1000C.
Based on temperature the microorganisms are classified into 3 types

4. PSYCHROPHILES
MESOPHILES
THERMOPHILES

5. A) Psychrophiles
They are grow at 00C to 200C and optimum temp 150C.
They isolated from arctic and antarctic habitats. Because 90% is ocean.
The cell membrane of psychrophilic microorganisms have high levels of
unsaturated fatty acid and remain semifluid when cold.
If temperature is more than 150C the cell membrane will disrupts.
Eg: Pseudomonas vibrio

6. B. Mesophiles:
➢Grows best in moderate temperature.
➢Temperature range: 25°C to 40°C and optimum temp 37°C.
➢All pathogenic organisms, warm blooded animals are mesophiles. Examples: Escherichia
coli, Streptococcus pneumoniae, etc.
C. Thermophiles:
➢Derived from Greek word thermotita meaning heat and philia meaning love. Heat-loving
microorganisms.
➢Grow at 50°C to 80°C or higher. Their optimum temp is 45°C.
➢Extreme thermophiles grow at 1100C.
Examples: Thermus aquaticus, Geogemma barossii, etc.

7. ACIDOPHILES
NEUTROPHILES
ALKALOPHILES
PH

8. ACIDOPHILES
Grow between PH 0 and 5.5. Optimum PH 2.0 to 3.5
Examples: Ferroplasma, Thiobacillus thioxidans, Sulfolobus acidocaldarius, etc.
NEUTROPHILES
Grow between pH 5.5 to 8.0. Optimum PH 7.0 to 7.5
Examples: Lactobacillus acidophillus, E. coli, Pseudomonas aerunginosa, etc.
ALKALOPHILES
Grow between pH range of 7.5 to 14. Optimum PH 9.0 to 9.5
Examples: Thermococcus alcaliphilus, etc.

9. 3. Gaseous Requirement:
I. Aerobic: Microbes can grow in presence of oxygen
II. Anaerobic: Microbes can grow in absence of oxygen
III. Facultative anaerobes: Microbes can grow in both aerobic and anaerobic
conditions.
IV. Aerotolerant: Microbes ignore oxygen and grow equally well whether it is
present or not.
V. Microaerophilic: They require less oxygen concentration that that is present in
atmosphere

10. EFFECT OF OXYGEN ON THE GROWTH OF VARIOUS BACTERIA

11. OXYGEN TOXICITY
1. Oxygen inactivation of enzymes: Molecular oxygen can directly oxidize
certain essential reduced groups, such as thiol [-SH] groups or enzymes
resulting in inactivation of enzymes.
2. Damage due to toxic derivatives of oxygen: Various cellular enzymes
catalyze chemical reactions involving molecular oxygen. Some of these reactions
result in addition of a single electron to an oxygen molecule, thereby forming
superoxide radical [O2.-]:
O2 + e- O2.- (1)

12. Superoxide radicals can inactivate vital cell components. Accumulation of these
molecules is leads to even more toxic substances such as hydrogen peroxide [H2O2]
and hydroxyl radical [OH.]
2O2.- + 2H+ O2 + H2O2 (2)
chelated iron
O2.- + H2O2 O2 + OH- + OH
. (3)

13. Aerobic and facultative organisms possess superoxide dismutase enzyme which
eliminates superoxide radicals. The hydrogen peroxide produced by this reaction can
in turn be dissipated by catalase and peroxidase enzymes. But anaerobic bacteria lack
this enzymatic system. Hence oxygen is toxic to anaerobic bacteria.
Catalase
2H2O2 2H2O + O2 (4)
Peroxidase
H2O2 + reduced substrate 2H2O + oxidized substrate (5)

14. CULTIVATION OF ANAEROBIC BACTERIA
The culture media is boiled for several
minutes to drive off the dissolved oxygen.
A reducing agent eg., cysteine is added to
further lower the oxygen content.
Oxygen free nitrogen is bubbled through the
medium to keep it anaerobic.
1. PREREDUCED MEDIA

15. S absence
a.) Glove ports and rubber gloves that
allows operator to perform
manipulations within the chamber.
b.) Air lock with inner and outer
doors.
c.) Air in the chamber is replaced with
nitrogen
d.) The inner door is opened and
media are placed within the
chamber, which contains an
atmosphere of H2+CO2+N2.
e.) A circulator which circulates the
gas atmosphere through pellets of
palladium catalysts
2. ANAEROBIC CHAMBER

16. 3. ANAEROBIC JAR
Media are inoculated and then placed in the jar.
Water is added to the GasPak generator envelope
causing the evolution of H2 and CO2.
The H2 reacts with O2 on the surface of the
palladium catalyst, forming water and
establishing anaerobic conditions. The CO2 aids
the growth of fastidious anaerobes which
sometimes fail to grow or grow only poor, in it
absence.

17. REFERENCES
1. Prescott, Harley and Klein's, Microbiology. 5th edition. 121-130.
2. Gerard J. Tortora, Berdell R. Funke, Christine L. Case.
Microbiology – An Introduction. 10th edition. Pearson. 157-168.
3. Michael J. Pelczar, JR., E.C.S. Chan, Noel R. Krieg.
Microbiology. 5th edition. 99-114.