Transcript Growth and multiplication in bacteria
GROWTH AND PHYSIOLOGY OF BACTERIA
Mrs.Rashmi.S
GROWTH
Defined as the orderly increase in the quantity of the cellular components or structures, followed by cell division Bacteria divide by binary fission
Generation Time The time required for a cell to divide or for the population to double .
1 2 4 8 16
Two types of bacterial counts Total count: Total number of cells in the sample Viable count: Number of living cells capable of multiplication
Total count is obtained by: Direct Microscopic counting.
Coulter counter.
Nephalometer.
Determination of the Cell Mass.
Measurement of cell Nitrogen.
Viable count: 1.
Determination of cells by Plate Count 2.
Membrane Filter method
BACTERIAL GROWTH CURVE
Bacterial counts are made at intervals and plotted in relation to time.
Curve exhibits following phases 1.
Lag Phase 2.
3.
4.
Log Phase Stationary Phase Phase of decline
GROWTH CURVE
LAG PHASE:
Characterized by a period during which there is no increase in the number of cells.
Cells enlarge ,as enzymes and metabolic intermediates are built up Duration of Lag phase varies with the Spp., size of the inoculum, nature of the culture medium and environmental factors .
LOG OR EXPONENTIAL PHASE:
Cells start dividing Number increase exponentially by geometric progression with time.
If log of number of cells plotted against time, results in a straight line
STATIONARY PHASE :
Cell division stops due to depletion of nutrients and accumulation of toxic products.
Balance is maintained between cell division and cell death Viable count remains stationary for some time.
PHASE OF DECLINE :
Phase of decrease in the cell number due to cell death Total count continues with out decline.
Viable count decreases
Continuous culture
Maintaining microbial population in logarithmic phase of growth in a constant environment .
Methods of Continuous culture
CHEMOSTAT TURBIDOSTAT
Bacterial Nutrition
Bacteria are classified nutritionally into: PHOTOTROPHS CHEMOTROPHS AUTOTROPHS HETEROTROPHS
Based on Oxygen requirements bacteria are classified into: AEROBES (Eg: Vibrio) ANAEROBES (Eg: Clostridium) MICROAEROPHILLIC (Eg: Helicobacter)
Based on Temperature requirements bacteria are classified into
MESOPHILLIC THERMOPHILLIC PSYCHROPHILLIC
BACTERIAL METABOLISM
OXIDATION FERMENTATION O-R POTENTIAL
FACTORS INFLUENCING BACTERIAL GROWTH
Carbondioxide Temperature Moisture and Drying H + ion concentration Light Osmotic Effect Mechanical and Sonic Stress
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