Transcript Bacterial Growth

Orderly increase of all of the chemical constituents of
the cell.
Bact.growth-both an increase in the size and no. of the cells.
Net effect an increase in the total mass i.e.biomass.
Bacteria divide by binary fission.
Nuclear division precedes cell division.
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Chemical requirements( macro n micronutrients)
Growth factors(essential n accessory) like thiamine,
riboflavin,nicotinic acid, folic acid, B12.
Physical factors: Environmental conditions: temperature,
pH, osmotic pressure,oxygen,co2,moisture n drying,light,
mechanical n sonic stresses.
Energy sources( photo n chemotrophs)
Generation time( interval of time between two cell divisions
or time required for a bacterium to give rise to two
daughter cells under optimal conditions.)
 Major elements (CHONPS + K, Mg, Fe, Ca)
Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus,
potassium, magnesium, iron, and calcium
Organisms classified based on carbon usage
 Heterotrophs
Use organic carbon as nutrient source.
 Autotrophs
Use inorganic carbon (CO2) as carbon source
 Trace elements (Co, Cu, Ni, Zn, Se, Mg, Wo)
 Cobalt, zinc, copper, molybdenum and manganese
 Required in minute amounts
 Assist in enzyme function
 Nutritional diversity
 Different organisms require the same nutrients but may require
different forms of the nutrients
Element
% dry wgt
Source
Carbon
50
organic compounds or CO2
Oxygen
20
H2O, organic compounds, CO2, and O2
Nitrogen
14
NH3, NO3, organic compounds, N2
Hydrogen
8
H2O, organic compounds, H2
Phosphorus
3
inorganic phosphates (PO4)
Sulfur
1
SO4, H2S, So, organic sulfur compounds
Potassium
1
Potassium salts
Magnesium
0.5
Magnesium salts
Calcium
0.5
Calcium salts
Iron
0.2
Iron salts
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Carbon sources
◦ CO2
◦ organic
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autotroph
heterotroph
Energy sources
◦ sunlight
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phototroph
◦ organic =
chemotroph
◦ Derive both carbon and energy from organic
compnds(chemohetero)
Derives energy from organic compounds and
carbon source from inorganic compounds
A related ancient group…..
Lithoautotroph
Neither sunlight nor organics used, rather
it relies totally on inorganics
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Saprobe – lives on organic matter of dead
organisms
Parasite – lives on organic matter of living
host = pathogens
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Temperature
O2
CO2
pH
Osmotic Pressure(plasmolysis n plasmotysis)
Moisture n drying( lyophilization or freeze drying)
Light
Mechanical n sonic stresses.(grinding n vigorous
shaking with glass beads)
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Psychrophiles: cold-loving
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Mesophiles: moderate temperature-loving
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Thermophiles: heat-loving
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Each has a minimum, optmum, and maximum
growth temperature
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Optimum growth temperature is usually near
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Death above the maximum temp. comes from
enzyme inactivation
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Mesophiles most common group of organisms
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40ºF (5°C) slows or stops growth of most
microbes
the top of the growth rang
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Obligate aerobes – require O2.e.g
pseudomonas,vibrio.
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Facultative anaerobes – can use O2 but also
grow without it.ecoli n staph.
Obligate anaerobes – die in the presence of
O2.clostridia n bacteroides.
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Most bacteria grow between pH 6.5 and
7.5
Acid (below pH 4) good preservative for
pickles n cheeses
Acidophiles can live at low pHe.g
lactobacillus.
Vibrio grows at alkaline pH
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Bacteria divide by binary fission.
No mitosis
Colony: clone of cell derived from a single
parent..millions of bacteria in a single colony
Colonies on soid media
Diffuse growty in liquid media
Logarithmic growth,geometric progression or
exponential growth
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Time required for cell to divide/for
population to double
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Average for bacteria is 1-3 hours
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E. coli generation time = 20 min
◦ 20 generations (7 hours), 1 cell becomes 1
million cells!
◦ Tubercle bacilli 20 hrs
◦ Lepra bacilli 20 days
1.Lag phase
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After inoculation of microorg.in fresh culture
medium, no immediate increase in cell no.
Increase in cell size but no cell division, cells r not
dormant
making new enzymes in response to new
medium(adaptation)
Variable in length
2.Log phase :
exponential growth
◦ Desired for production of products
◦ Most sensitive to drugs and radiation during this
period
◦ Population is most uniform in physiological n
chemical properties
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Stationary phase –
◦ nutrients becoming limiting or waste products
becoming toxic,changes in Ph,decreased o2 tension
◦ death rate = division rate
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Death phase – death exceeds division