BACTERIAL NUTRITION AND BACTERIAL GROWTH Flashcards
lowest temp at w/c the organism can grow
Minimum temperature requirement
temp at w/c organisms grow best
Optimum temperature requirement
highest temperature at w/c organisms can grow
Maximum temperature requirement
Min 0oC
Opt 15 oC
Max 20 oC
Psychrophile
Min 45 oC
Opt 50 – 60 oC
Max 250 oC
Thermophile
Min 15 – 20 oC
Opt 20 – 40 oC
Max 45 oC
Mesophile
normal range of pH
7.35-7.45
grows in pH below 4
Acidophile
grows in pH greater than 8
Alkalinophile
grows in pH 6.5 to 7.5
Neutrophile
Bacteria often produce [?] that could inhibit their own growth
acids
To maintain the proper pH, [?] are included in the medium
buffers
Requires higher osmotic pressure; Not pathogenic
Osmophile
require higher conc. of salts (30%); live in sea water
Halophile
Can withstand an environment with high salt concentration (2%)
Halotolerant
“extreme halophiles”
Osmophile
“obligate halophiles”
Halophile
“facultative halophiles”
Halotolerant
example of Halophile
Vibrio parahaemolyticus
example of Halotolerant
Staphylococcus aureus
Major Elements
Carbon Hydrogen Oxygen Nitrogen Sulfur
Minor Elements
Phosphorus Potassium Magnesium Iron Calcium
Trace Elements
Manganese Cobalt Zinc Copper Molybdenum
Growth Factors
Purines and Pyrimidine
Amino acids
Vitamins
Structural backbone of living matter
CARBON
Needed for all organic compounds
CARBON
Half of the dry weight of bacteria is made up of
CARBON
Used in protein synthesis
Nitrogen and Sulfur
Use in DNA and RNA synthesis
Nitrogen and Phosphorus
Use of gaseous nitrogen directly from the atmosphere
Nitrogen Fixation
Synthesize sulfur containing amino acids and vitamins such as THIAMINE and BIOTIN
Sulfur
Synthesis of nucleic acids
Phosphorus
Phospholipids of cell membrane
Phosphorus
ATP synthesis
Phosphorus
Cofactor for enzymes
Phosphorus
poisonous to organism
OXYGEN
dependent on enzyme systems
OXYGEN
inability to convert this element can cause problems
OXYGEN
TOXIC FORMS OF OXYGEN
Singlet Oxygen
Superoxide Radicals
Peroxides
Hydroxyl radicals
normal molecular form of oxygen in a higher energy state
Singlet Oxygen
“superoxide anions”
Superoxide Radicals
formed in small amount during respiration
Superoxide Radicals
highly unstable
Superoxide Radicals
from hydrogen peroxide produced from the neutralization of superoxide radicals
Peroxides
most reactive form
Hydroxyl radicals
formed in the cytoplasm by ionizing radiation
Hydroxyl radicals
GROUPS OF BACTERIA ACCORDING TO OXYGEN REQUIREMENT
AEROBES
ANAEROBES
MICROAEROPHILES
CAPNOPHILES (CAPNEIC)
require constant exposure to oxygen
Obligate aerobes
primarily anaerobe that can tolerate the presence of oxygen
Facultative aerobes
has enzymes that convert toxic oxygen derivatives
AEROBES
converts molecular oxygen to hydrogen peroxide
Superoxide dismutase
Hydrogen peroxide is still toxic so it is converted to water and oxygen
Catalase
requires an envi completely free of oxygen
Obligate anaerobes
primarily anaerobe that can tolerate the absence of oxygen
Facultative anaerobes
lives in the absence of oxygen
ANAEROBES
lacks the enzymes SOD and CAT
ANAEROBES
accumulation of toxic oxygen radicals may inhibit growth
ANAEROBES
refers to bacteria that requires low concentrations of oxygen (2 – 7%)
MICROAEROPHILES
cannot grow in the presence of 20 – 21% oxygen
MICROAEROPHILES
cannot grow in the absence of oxygen
MICROAEROPHILES
requires higher concentrations of carbon dioxide (3 – 5%)
CAPNOPHILES
normal concentration of carbon dioxide (1%)
CAPNOPHILES
refers to an increase in bacterial number, not an increase in the size
Bacterial growth
mode of reproduction
Binary Fission
most common method of reproduction of most bacteria
Binary Fission
the interval of time between the successive binary fission of a cell or population
Generation time
time required for a cell to divide and its population to double
Generation time
GT for S. aureus
15 mins
GT for M. tuberculosis
15 hrs
GT for T. pallidium
33 hrs
depends on the condition the bacteria is in
Generation time
optimum condition:
faster GT
As a cell divides, the population
increases
Numerically this is equal to 2 because one cell divides into two raised to the
number of times the cell divided (generations)
GT is useful in determining the [?] before disease symptoms
appear
amount of time that passes
GT is useful in determining the effect of a newly developed [?] on the culture
preservative
PHASES OF GROWTH
Lag phase
Log phase
Stationary phase
Decline phase
adapting to new environment
Lag phase
synthesis of enzyme
Lag phase
no growth rate
Lag phase
Phase of physiologic youth
Lag phase
intense metabolic activity
Lag phase
synthesis of enzymes and various molecules
Lag phase
undergoes binary fission at the fastest rate
Log phase
has the shortest and constant generation time
Log phase
“exponential phase”
Log phase
phase of balanced growth
Log phase
Log phase events:
o symptoms of infection
o appearance of colonies
susceptible to certain antibiotic action
Log phase
separate -> manufacturing of cell wall = interruption to antibiotic action
Log phase
has the highest number of cell
Stationary phase
reproduction = death
Stationary phase
“plateau phase”
Stationary phase
factors of death in Stationary phase
o nutrient depletion
o pH change
o waste accumulation
o acid production
unfavorable envi for growth
production of spores
negative exponential growth
Decline phase
dead cells > viable cells
Decline phase
IN-VITRO ENVIRONMENT
Batch culture system
Continuous culture system
single batch of medium only
Batch culture system
no additional nutrients are added
Batch culture system
waste products are not removed
Batch culture system
“open culture system”
Continuous culture system
Addition of nutrients; Removal of waste
Continuous culture system
sterile medium is fed into the culture vessel at the same rate as the media containing the organism is removed
Chemostat
has a photocell that measures the absorbance or turbidity of the culture in the growth vessel
Turbidostat
METHODS OF DETERMINING BACTERIAL GROWTH
DIRECT METHOD
Direct cell count
Plate count
Membrane Filter technique
METHODS OF DETERMINING BACTERIAL GROWTH
INDIRECT METHOD
Turbidity
Determination of Dry weight
Petroff-Hausser Counting Chamber
Direct cell count
easy, cheap
Direct cell count
gives the size and morphology
Direct cell count
disadvantage: microbial population must
be fairly large for accuracy because it
require a small volume only
Direct cell count
“viable cell counts”
Plate count
Simple and sensitive
Plate count
Prone to inaccurate counts
Plate count
Plate count is expressed in
COLONY FORMING UNITS
CFU
to ensure that some colony counts will be within the range of 30 – 300 colonies; to ensure that some colony counts will be within the range of 30 – 300 colonies
SERIAL DILUTIONS
2 methods of Plate count
o Pour Plate Method
o Spread Plate Method
Done on colonies growing on special membrane filters having pores designated to trap bacteria
Membrane Filter technique
Measures the amount of light that is
transmitted or absorbed through a
solution
Turbidity
Turbidity
Absorbance is DIRECTLY PROPORTIONAL to
bacterial growth
Cells growing in liquid medium are collected by centrifugation, washed, dried in the oven and weighed
Dry weight
