bacterial nutrition

1. Bacterial
nutrition
Prepared By:
Mrs. Pragya Prasad

2. Bacterial Nutrition
• Bacterial cell has its principle
constituent as water(80%) of total
weight.
• Rest is protein, polysaccharides, lipids,
nucleic acids, mucopeptides.

3. Minimum requirement for
growth & multiplication of
bacteria
• Water
• A source of carbon
• Nitrogen
• Inorganic salts
• Water is the vehicle for the entry of all
nutrients into cell and elimination of water.

4. Classification
• Phototrophs : derive energy from
sunlight
• Chemotrophs : obtain energy from
chemical reactions
• Autotrophs : synthesize all organic
compounds
• Heterotrophs : unable to synthesize and
depend on performed organic
compounds.

5. Bacterial requirements
• Oxygen
• Carbon dioxide
• Temperature
• Moist & drying
• H-ion concentration
• Light
• Osmotic effect
• Mechanical and sonic stress

6. Oxygen requirement
• Division is based on influence of oxygen into
growth.
• Aerobic: require o2 for growth
• Anaerobic: growth in absence of oxygen
• Microaerophilic: grow best in low o2 tension.
• Facultative anaerobes: ordinarily aerobic but
can grow in absence of oxygen.
• Aerobic obtain energy through oxidation
• Anaerobes use hydrogen than oxygen

7. CO2
• All require small amount of Co2
• Requirement usually met by co2 in
atmosphere

8. Temperature
• Bacteria vary in requirement of temperature for
growth
• For each species there is a temperature range and
growth does not occur above maximum or below
minimum
• Optimum temperature: temperatute at which growth
occurs best(370
C)
• Mesophilic: Bacteria grow best at 25-400
C.
• Psychrophilic: grow best at temperature below 200
C
eg.(-70
C)
• Thermophies: grow best at higher temperature.(55-
800
C).
• Extreme thermophilic bacteria can grow at 2500
C.
• Thermal death point: lowest temperature that kills a
bacteria under standard condition in a given time.
• At low temperature some species die rapidly but most

9. Moist and drying
• Water is essential to bacterial
protoplasm and drying is lethal
• Treponema is highly sensitive to drying
while other withstand drying for
months.
• Spore may survive in dry state for
several decades.

10. H-ion concentration
• Bacteria are sensitive to variation in pH.
• Each bacteria ahas a pH range, above or
below to that bacteria cant survive.
• Optimum pH are at which bacteria
grows best.
• Bacteria grows best at neutral or
slightly alkaline (pH-7.2-7.6.

11. Light
• Bacteria (except phototropic) grow well
in dark.
• They are sensitive to UV light and
radiations.
• Cultures die if exposed to sunlight.

12. Osmotic effect
• Bacteria are more tolerant to osmotic
variation than most other cells due to
strength of their cell wall.
• Sudden exposure to hypertonic solution
may cause withdrawal of water and
shrinkage of protoplasm (plasmolysis).
• Sudden transfer from a concentrated
solution to a distilled water may cause
plasmoptysis (excess osmotic inhibition
leading to rupture of cells.)

13. Mechanical and sonic stress
• Bacteria have tough cell walls, they may
be ruptured by mechanical stress such
as grinding or vigorous shaking by glass
beads.

14. Thank you