Requirements for Growth/Multiplication
ALL required nutrientscorrect
pH temperature salinity, moisture redox potential atmosphere
GrowthLiquid vs Solid Media
Liquid: clear >>turbidSolid: individual colonies
each colony derived from a single cell
Growth Event
Absorption of water & nutrientsCatabolism of carbon source
inorganic or organic
Biosynthesis of new cellular components major energy consumption
Cell enlargementCell division ( Binary Fission)
Binary Fission
DNA replicationPlasma membrane invaginateCell wall deposited in invaginated spaceCross wall completedCells separate
Consequences of Binary Fission
Very large number of cells very fastMathematical 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
Logarithmic Plots
Can plot very large Range of numbersPhases of growth demonstratedGeneration time easily calculated
Mathematics of bacterial growth
Generation # Log 2 Log10
0 1 0 0.0001 2 1 0.3012 4 2 0.6023 8 3 0.9034 16 4 1.2045 32 5 1.505 6 64 6 1.8067 128 7 2.1078 256 8 2.408
Cells
Growth curves for exponentially increasing population
Time (hours)
Number of cells
Log number of cells
Calculation of Generation Time
1 5 10Time (hours)
Log phase
Double # cells
Generation time
Log Number of Bacteria
Slope of Log phase proportional to generation time
Time (hours)
Log Number of bacteria
SlowDoubling number
Medium
Fast
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
Sample calculation for K & G
Population increase from 103 to 109 in 10hrsK= (log 109 - log 103) / 0.301 x 10K= 9-3/3.01 = 2 generations/hours
G = 1/K = 1/2 = 0.5 hr/generation
Factors influencing lag phaseAge 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
10 20 30 40 50 60-10 0 70 80 90 100
Temperature (o C)
Rate of Growth
Mesophile
PyschrophilePsychrotroph
Thermophile
Extreme Thermophile
Growth Responses: Temperature
Diauxic Growth
Growth on two carbon sourcesMixed sugarsEach sugar used separatelyGlucose ALWAYS used firstSecond sugar ONLY used when glucose
GONE
Synchronous Growth
Filtration Smaller cells all same size
Temperature shock Hot/cold brings cells to same metabolic state
Starvation deplete medium of selected nutrient
Synchronous vs Asynchronous growth
Time (min)
Number of Cells
Asynchronous growth
Synchronous
growth
Growth in Limited Nutrients
Limiting concentration of Required nutrientYIELD number of cellsLinear increase yield with nutrient conc
Yield = Mass of organisms formed
Mass of nutrients used
Bio-Assay: ProcedureBacterium: CANNOT synthesize nutrientMedium: all growth requirements except nutrient to be
assayedAdd
equal amounts of medium to each tube equal numbers of bacteria to each tube increasing amounts of the nutrient to be assayed
[Unknown]IncubateMeasure growth (turbidity or viable count)
Bio-Assay
[Nutrient] g/ml
Microbial Growth 0
Growth of unknown
0
0
0
0
Growth of known [nutrient]
[Nutrient] in unknown
Vitamin B-12 measurement in Green beans Lactobacillus leichmanni
Chemostat: PrincipleEssential nutrient is limitedGrowth rate(K) controlled by supply rate of nutrientYield controlled by concentration of nutrientDilution rate (D): speed of nutrient flow into the
culture vessel
Flow rate
Vessel volume
D = Steady State
K = D
Chemostat: Sample Results
Dilution Rate of Nutrient
Measurement
Value Generation time
Nutrient conc
Cell density or biomass
Chemostat: ApplicationsGrowing large amounts of cellsIndustrial production
vaccines pharmaceuticals hormones
Long term studies of specific growth phaseSelecting for specific mutantsAquatic systems
Bacterial Growth in Natural Environments
Natural Environments Animal Tissues Soil Water- freshwater- marine Plants
Bacterial Growth in Natural Environments
Active Short bursts of growth & metabolism usually low rates of growth
Quiescent Viable cannot culture
Stressed starvation semi viable
Biofilms: Body Catheter
Foley: • latex silicone
Intravenous:• polyurethane S. epidermidis
Prostheses Hip joints Dental implants voicebox
TamponsIUD