BACTERIA GROWTH

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BACTERIA GROWTH CULTURE BACTERIA ARE
UBIQUITOUS, THEREFORE, THEY CAN BE ISOLATED FROM
ANY ENVIRONMENT ON EARTH. WE MUST, THEREFORE,
APPRECIATE THEIR VARIED HABITATS STRATEGIES
USED IN ADAPTING TO DIFFERENT HABITATS . TO
BEST STUDY BACTERIA, WE MUST BE ABLE TO GROW THEM
IN CULTURE. FACTORS AFFECTING THEIR
GROWTH MAY BE PHYSICAL NUTRITIONAL AND AS SUCH
THEY MAY BE CLASSIFIED BASED ON THESE FACTORS.
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BACTERIA GROWTH CULTURE PHYSICAL FACTORS
pH, Temperature, Oxygen, Moisture, Osmotic
Pressure Radiation pH (ACIDOPHILES,
NEUTROPHILES AND ALKALIPHILES) INDICATE pH
optimum Acidophiles OPTIMUM pH lt
4 Neutrophiles OPTIMUM pH 6 -
7 Alkaliophiles OPTIMUM pH 8 to
9 TEMPERATURE MOST SPECIES OF BACTERIA MY
TOLERATE A 30O TEMPERATURE RANGE. BASED ON THE
TEMP RANGE THEY MAY BE CLASSIFIESD AS
Psychrophiles 15o to 20oC (many grow well at
0oC) None inhabit the human body but some
cause spoilage of refrigerated foods.
Mesophiles 25o to 40oC (human pathogens
included in this group). Thermophiles 50o to
60oC (Many found in compost heaps a few even
tolerate temperatures as high as 110oC).
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BACTERIA GROWTH CULTURE
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BACTERIA GROWTH CULTURE Oxygen Aerobes
Require oxygen to grow Anaerobes Do not
require oxygen for growth Obligate aerobes
Must have free O2 for respiration. Obligate
or strict anaerobes killed by free
O2. Microaerophiles grow best in presence
of small amounts of free O2. Facultative
anaerobes carry out aerobic respiration when
O2 is present but shifts to anaerobic respiration
in its absence. Aerotolerant anaerobes
Survive in the presence of O2 but do not use
it in their metabolism.
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BACTERIA GROWTH CULTURE
Note aerobic growth at top of broth
Note aerobic growth lower in broth
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BACTERIA GROWTH CULTURE
Example 2 Growth in agar
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BACTERIA GROWTH CULTURE WHY IS OXYGEN TOXIC TO
SOME BACTERIA? IT MAY INACTIVATE PROTEINS (e.g.,
inactivation of sulfhydryl groups due to
oxidation) PRODUCTION OF TOXIC OXYGEN
DERIVATIVES (e.g., O2 e- -----gt O2-.
(superoxide radical) O2-. e- 2H -----gt
H2O2 (hydrogen peroxide) H2O2 e- H -----gt
H2O OH. (hydroxyl radical) Superoxide
radical, hydrogen peroxide hydroxyl radical are
extremely toxic. They are powerful
oxidizing agents Hydroxyl radical are most
toxic With half life of micro-seconds They react
with most organic molecules resulting in their
destruction Obligate aerobes facultative
anaerobes protect themselves because the possess
the enzymes SUPEROXIDE DISMUTASE CATALASE
2O2-. 2H ---SUPEROXIDE DISMUTASE-------------
--------gt O2 H2O2 2H2O2 ---CATALASE--------
-------------gt 2H2O O2
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BACTERIA GROWTH CULTURE AEROTOLERANT
BACTERIAMAY LACK CATALASE BUT ALMOST ALWAYS HAVE
SUPEROXIDE DISMUTASE ALL STRICT ANAEROBES LACK
BOTH ENZYMES HAVE NO STRATEGY TO DEAL WITH
TOXIC OXYGEN PRODUCTS
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BACTERIA GROWTH CULTURE SHIFTING BATERIA TO
EXTREME TEMPERATURES (1) RESULT IN DISRUPTION
OF MEMBRANE PEARMEABILITY DUE TO INCREASED
FLUIDITY OF THE LIPID BILAYER. (2) LEADS TO
LOSS OF SOLUTES. (3) HIGH PROTON PERMEABILITY
(LOSS OF PROTON CIRCUIT) ADAPTATION TO EXTREME
TEMPERATURES BY THERMOPHILES REQUIRE (1) ENZYME
SYSTEMS THAT TOLERATE HIGH TEMPERATURES (2)
CHANGES IN THE LIPID COMPOSITION TO MAINTAIN
MEMBRANE FLUIDITY - AT LOW TEMPERATURE,
SHORT-CHAIN FATTY ACIDS UN-SATURATED FATTY ACIDS
USED (HELPS MEMBRANE TO REMAIN FLUID DUE TO
KINKS THAT HELP TO PREVENT CLOSE PACKING OF OF
LIPID CHAINS). BRANCHED CHAIN FATTY ACIDS ARE
SOMETIMES REPLACE THE UNSATURATED FATTY ACIDS. -
AT HIGH TEMPERATURES SATURATED FATTY ACIDS USED
IN MEMBRANE.
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BACTERIA GROWTH CULTURE
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BACTERIA GROWTH CULTURE pH HOMEOSTASIS
(MAINTAINING CYTOPLASMIC pH (pHi ) DESPITE
FLUCTUATIONS IN IN THE EXTERNAL pH). - THE
CYTOPLASMIC MEMBRANE ACTS AS FIRST BARRIER SINCE
IT IS RELATIVELY IMPERVIUS TO IONS. -
ACIDOPHILES NEUTROPHILES USE PROTON PUMPS
POTASSIUM TRANSPORT SYSTEMS TO MAINTAIN pHi IN
NEUTRAL RANGE. - ALKALOPHILES Na CIRCUITS
ARE OF MAJOR IMPORTANCE.
Alkalophiles exchange internal Na Ions for
external H
Neutrophiles acidophiles exchange K for H
using antiport transport system
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BACTERIA GROWTH CULTURE BACTERIA GROWTH IN
CULTURE TWO TYPES OF CULTURES (1) BATCH
CULTURE OR CLOSED SYSTEM - SINGLE BATCH
OF GROWTH MEDIA IN CLOSED VESSEL - NO
FRESH MEDIA ADDED - DURING INCUBATION,
NUTRIENT CONCENTRTION DECLINES AS
WASTE CONCENTRATION INCREASED (2) CONTINUOUS
CULTURE OR OPEN SYSTEM - CONTINUAL
PROVISION OF NUTRIENTS - CONTINUAL
REMOVAL OF WASTE - EXPONENTAL GROWTH
MAINTAINED FOR EXTENDED PERIOD
- MAINTAINS CONSTANT BIOMAS CONCENTRATION (
OF CELLS) - TWO MAJOR TYPES
OF SYSTEMS (A) CHEMOSTAT (B)
TURBIDOSTAT BACTERIA REPLICATION IS BY BINARY
FISSION GROWTH CAN BE PLOTTED AS THE
LOGARITHYM OF CELL VERSUS INCUBATION TIME
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BACTERIA GROWTH CULTURE
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BACTERIA GROWTH CULTURE WHEN BACTERIA ARE
INTRODUCED INTO FRESH CULTURE MEDIUM THE GROWTH
CURVE FOR A BATCH CULTURE HAS FOUR PHASES (1)
LAG PHASE (2) LOG OR EXPONENTIAL PHASE (3)
STATIONARY PHASE (4) DEATH PHASE LAG (A
RETOOLING PERIOD) MAY BE DUE TO SWITCHING FROM
ONE MEDIUM TO ANOTHER, REQUIRING NEW ENZYME
SYNTHESIS CELLS MAY REQUIRE THE SYNTHESIS OF NEW
FACTOR, RIBOSOMES OR ATP NO INCREASE IN
CELL OCCURS PHASE VARIES IN LENGTH DEPENDING
ON THE CONDITIONS FROM WHICH THE INNOCULUM IS
TAKEN (OLD VS NEW CULTURE SWITCHING FROM MEDIUM
WITH A DIFFERENT COMPOSITION e.g., GLUCOSE AS
CARBON ENERGY SOURCE TO LACTOSE AS CARBON
ENERGY SOURCE)
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BACTERIA GROWTH CULTURE EXPONENTIAL PHASE RATE
OF GROWTH AND DIVISION IS MAXIMUM RATE OF GROWTH
IS CONSTANT, i.e., DOUBLING OCCURS AT REGULAR
INTERVALS CELLS ARE MOST UNIFORM IN CHEMICAL
PHYSIOLOGICAL PROPERTIES STATIONARY
PHASE POPULATION GROWTH CEASES (DEATH RATE
REPLICATION RATE) OCCURS IN BACTERIA CULTURES AT
CONCENTRATIONS ABOUT 109 CELLS/ml FACTORS THAT
TRIGGER THIS PHASE INCLUDE - ESSENTIAL NUTRIENT
DEPLETION, - OXYGEN (AEROBES)DEPLETION, -
TOXIC WASTE ACCUMULATION (e.g., ORGANIC ACIDS DUE
TO FERMENTATION VERY SIGNIFICANT IN
ANAEROBIC CULTURES DEATH PHASE DEATH RATE
GREATER THAN REPLICATION RATE CELL NUMBER MAY
NOT APPEAR TTO DECREASE EXPONENTIALLY DUE TO LACK
OF LYSIS. VIABILITY COUNT IS NECESSARY TO
CONFIRM DEATH