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Growth and Multiplication of Bacteria

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Presentation on theme: "Growth and Multiplication of Bacteria"— Presentation transcript:

1 Growth and Multiplication of Bacteria
Hugh B. Fackrell Sept 1997 Filename: Growth.ppt

2 Requirements for Growth/Multiplication
ALL required nutrients correct pH temperature salinity, moisture redox potential atmosphere

3 Growth Liquid vs Solid Media
Liquid: clear >>turbid Solid: individual colonies each colony derived from a single cell

4 Growth Event Absorption of water & nutrients
Catabolism of carbon source inorganic or organic Biosynthesis of new cellular components major energy consumption Cell enlargement Cell division ( Binary Fission)

5 Binary Fission DNA replication Plasma membrane invaginate
Cell wall deposited in invaginated space Cross wall completed Cells separate

6 Binary Fission Light micrograph

7 Binary Fission

8 Consequences of Binary Fission
Very large number of cells very fast Mathematical progressions arithmetic (1>2>4>6>8>10>12>14>16) geometric(1>2>4>8>16) exponential expression (20 > 21 > 22 >23>24) logarithmic expression(0 >log21>log22>log23>log24

9 Logarithmic Plots Can plot very large Range of numbers
Phases of growth demonstrated Generation time easily calculated

10 Cell Multiplication 1 20 0 l 2 21 log21 ll 4 22 log22 llll
log23 lllllllll log24 lllllllllllllllll

11 Mathematics of bacterial growth
Cells Generation # Log Log10

12 Growth Data #Generation #cells Log10 1 1 0 5 32 1.51 10 1,024 3.01
, , ,048,

13 Growth curves for exponentially increasing population
Number of cells Log number of cells Time (hours)

14 Bacterial Growth Curve
Stationary phase Death phase Log phase Lag phase 1 5 10 Time (hours)

15 Measurement of Growth Constants
G: Generation Time K: Mean Growth Rate Constant G := 1/K

16 G: Generation time Time in minutes or hours for a population of bacteria to double in number

17 Calculation of Generation Time
Log Number of Bacteria Log phase Double # cells Generation time 1 5 10 Time (hours)

18 Slope of Log phase proportional to generation time
Time (hours) Log Number of bacteria Fast Medium Doubling number Slow

19 K: Mean Growth Rate Constant
K= n/t K= (log10Nt - log10Nt0)/ 0.301t N= number of cells n=: number of generations t = time (hr or min) K = 1/slope ( semi log growth plot) Therefore G = 1/K

20 Sample calculation for K & G
Population increase from 103 to 109 in 10hrs K= (log log 103) / x 10 K= 9-3/3.01 = 2 generations/hours G = 1/K = 1/2 = 0.5 hr/generation

21 Factors influencing lag phase
Age of culture inoculum old culture -> long lag young culture-> short lag Size of inoculum few cells -> long lag many cells -> short lag Environment pH, temp, gases,salinity sub optimum -> long lag optimum-> short lag

22 Growth Responses: Temperature
Rate of Growth Thermophile Mesophile Extreme Thermophile Psychrotroph Pyschrophile -10 10 20 30 40 50 60 70 80 90 100 Temperature (o C)

23 Growth Responses: pH pH Rate of Growth Neutrophile Alkalophile
Acidophile 1 2 3 4 5 6 7 8 9 10 11 12 pH

24 Diauxic Growth Growth on two carbon sources Mixed sugars
Each sugar used separately Glucose ALWAYS used first Second sugar ONLY used when glucose GONE

25 Diauxic Growth: 2 carbon sources
[Sugar] Arabinose Glucose Time (hr)

26 Synchronous Growth Filtration Temperature shock Starvation
Smaller cells all same size Temperature shock Hot/cold brings cells to same metabolic state Starvation deplete medium of selected nutrient

27 Synchronous vs Asynchronous growth
Number of Cells Asynchronous growth Synchronous growth Time (min)

28 Growth in Limited Nutrients
Limiting concentration of Required nutrient YIELD number of cells Linear increase yield with nutrient conc Yield = Mass of organisms formed Mass of nutrients used

29 Growth in Limited Nutrients
Total Growth Growth Rate [Nutrient]

30 Applications of Limiting [Nutrient]
Chemostat (continuous culture) Bio-Assay

31 Bio-Assay: Procedure Bacterium: CANNOT synthesize nutrient
Medium: all growth requirements except nutrient to be assayed Add equal amounts of medium to each tube equal numbers of bacteria to each tube increasing amounts of the nutrient to be assayed [Unknown] Incubate Measure growth (turbidity or viable count)

32 Bio-Assay Vitamin B-12 measurement in Green beans
Lactobacillus leichmanni Microbial Growth Growth of known [nutrient] Growth of unknown [Nutrient] in unknown [Nutrient] mg/ml

33 Chemostat Description of Instrument Principle Steady State
Sample Results Application

34 Chemostat: Description of Instrument

35 Chemostat: Principle Essential nutrient is limited
Growth rate(K) controlled by supply rate of nutrient Yield controlled by concentration of nutrient Dilution rate (D): speed of nutrient flow into the culture vessel Steady State K = D Flow rate Vessel volume D =

36 Chemostat: Sample Results
Measurement Value Cell density or biomass Nutrient conc Generation time Dilution Rate of Nutrient

37 Chemostat: Applications
Growing large amounts of cells Industrial production vaccines pharmaceuticals hormones Long term studies of specific growth phase Selecting for specific mutants Aquatic systems

38 Bacterial Growth in Natural Environments
Animal Tissues Soil Water- freshwater- marine Plants

39 Bacterial Growth in Natural Environments
Active Short bursts of growth & metabolism usually low rates of growth Quiescent Viable cannot culture Stressed starvation semi viable

40 Biofilms: Body Catheter Prostheses Tampons IUD Foley: Intravenous:
latex silicone Intravenous: polyurethane S. epidermidis Prostheses Hip joints Dental implants voicebox Tampons IUD

41 Biofilms: Water Dental lines Spacecraft Drinking filters ALL surfacces
Biofilm in gut of a mollusc

42 Biofilms: Disease Cystic fibrosis Ulcers Dental caries
lung-alveolar surface Ulcers Helicobacter jejuni Dental caries Streptococccus spp

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