EX. 8 Bacterial Growth and Nutrition Flashcards
Physical factors controlling microbial growth
Temperature, Oxygen, pH, and Osmotic conditions
Laboratory incubator is usually set at +35C to +37C
Mesophiles
What is required to be incorporated in the culture media ?
NaCl
Able to grow over wide ranges of water activity or osmotic concentration
Osmotolerant
Requires high levels of sodium chloride, usually above about 0.2M, to grow
Halophile
Growth optimum between pH 0 and 5.5
Acidophile
Growth optimum between pH 5.5 and 8
Neutrophile
Growth optimum between pH 8 and 11.5
Alkalophile
Grows well at 0C and has an optimum growth temperature of 15C or lower
Psychrophile
Can grow at 0-7C; has an optimum growth temperature between 20 and 30C and maximum around 35C
Psychrotroph
Growth optimum around 20-45C
Mesophile
Grow at 55C or higher, optimum often between 55 and 65C
Thermophile
Has an optimum between 80 and about 113C
Hyperthermophile
Completely dependent on atmospheric O2 for growth
Obligate aerobe
Grows equally well in presence or absence of O2
Aerotolerant anaerobe
Does not require O2 for growth, but grows better in its presence
Facultative anaerobe
Require O2 levels below 2-10% for growth and is damaged by atmospheric O2 levels (20%)
Microaerophile
Does not tolerate O2 and dies in its presence
Obligate anaerobe
Growth more rapid at hydrostatic pressures
Barophilic
Chemical requirements for controlling microbial growth
Carbon and energy sources, Carbon Dioxide, Inorganic and Organic ions
Requires increased CO2 (5-10%)
Capnophiles
Essential elements in all living cells
Carbon
Required for the synthesis of enzymes and other cellular proteins as well as nucleic acids
Nitrogen
Needed for nucleotides, the nucleic acids RNA and DNA, the energy storage molecule, ATP, and for structural phospholipids of the cell membrane
Phosphorus
Essential component of some amino acids from disulfide linkages between different parts of polypeptide chains and contribute to the folding of the chains into the correct secondary and tertiary protein structure
Sulfur
Trace elements
magnesium, iron, cobalt, phosphate, potassium
Sugar loving
Saccharophilic
Can only grow in an environment supplemented with a particular growth facto that is not required by wild strain (protoroph)
Auxotroph
Molecular arrangement (vitamin)
Cyanocobalamin (B12)
One-carbon metabolism
Folic acid
Transfer of acyl group
Lipoic acid
Precursor of coenzyme A
Pantothenic acid
Amino acid metabolism
Pyridoxine (B6)
Precursor of NAD and NADP
Niacin (nicotinic acid)
Precursor of FAD and FMN
Riboflavin (B2)
Substances that promote growth of the organism and are provided by various body fluids and tissues in vivo and form of yeast extract and blood or blood products in vitro
Growth factors
increase in bacterial numbers, not an increase in the size of the individual cells
Bacterial Growth
Period of Adaptation
Lag Phase
When the cell synthesizes new enzymes, cofactors, and essential metabolic intermediates, and the intercellular pools of nutrients are established
Lag Phase
Microorganisms are growing and dividing at the maximal rate possible
Logarithmic or exponential phase (Log phase)
Usually used in biochemical and physiological studies
Logarithmic or exponential phase (Log phase)
Rate of growth is constant
Logarithmic or exponential phase (Log phase)
This phase is “balanced growth” where all cellular constituents are manufactured at constant rates relative to each other
Logarithmic or exponential phase (Log phase)
The rates of synthesis of cell components vary relative to one another until a new balanced state is reached due to change in nutrient levels or other environmental conditions
Unbalanced growth
Where culture is transferred from a nutritionally poor medium to a richer one
Shift-up
There is lag while the cells first construct new ribosomes to enhance their capacity for protein synthesis
Shift-up
Culture is transferred from a rich medium to a poor one
Shift-down
There is a lag in growth because cells need time to make the enzymes required for the biosynthesis of unavailable nutrients
Shift-down
Phase where many important secondary metabolites are produces under the limited nutritional conditions
Stationary phase or phase of equilibrium
Cells living = Cells dying due to exhaustion of nutrients and the production of toxic metabolic products
Stationary phase or phase of equilibrium
Population growth eventually ceases
Stationary phase or phase of equilibrium
Attained by bacteria at a population level of around 10^9 cells per ml
Stationary phase or phase of equilibrium
- The result of a genetic response triggered in starving, stationary phase cells
- Cells become dormant without changes in morphology
- Once the appropriate conditions are available microbes resume growth
Viable but nonculturable (VBC)
- Fraction of microbial population is genetically programmed to die after growth ceases
- Some cells die and the nutrients the leak enable the eventual growth of those cells in the population that did not initiate cell death
- Dying cells are thus “altruistic” they sacrifice themselves for the benefit of the large population
Programmed cell death
Gradually the rate of the cell division stops completely, some of the cells die, so that the number of viable cells is reduced
Death phase/ Logarithmic decline phase/ phase of decline/ senescence
Incubated in a closed culture vessel with a single batch of medium
Batch culture
No fresh medium is provided during incubation
Batch culture
Observed in bacteria able to utilize two different carbon sources
Biphasic growth
System that can maintain a microbial population in exponential growth, growing at a known rate and constant biomass concentration for extended periods
Continuous culture system
Constructed so that the rate at which sterile medium is fed into culture vessel is the same as the rate at which the media containing microorganisms is removed
Chemostat
Possesses and essential nutrient in limiting quantities
Chemostat
Growth rate is determined by the rate at which new medium is fed into the growth chamber; the final cell density depends on the concentration of the limiting nutrient
Chemostat
Has a photocell that measures the turbidity (absorbance) of the culture in the growth vessel
Turbidostat
Flow rate of media through the vessel is automatically regulated to maintain a predetermined turbidty
Turbidostat
Time required for a cell to divide or population to double
Generation/doubling time
Generation time for Pseudomonas
14 minutes
Generation time for Staphylococcus aureus
30 minutes
Generation time for Mycobacterium tuberculosis
15 - 24 hours
Generation time for Treponema pallidum
33 hours
Useful in determining the amount of time that passes before disease symptoms appear in infected individuals
Generation/doubling time
A direct method used to measure volume of bacterial suspension is placed within a defined area on a microscope slide and are counted
Direct microscopic count
Advantages to this direct method are:
- easy, inexpensive, quick
- gives information about the size and morphology of microorganisms
Direct microscopic count
A disadvantage to this direct method is that to determine population size accurately, the microbial population must be relative large because only a small volume of the population is sampled
Direct microscopic count
Specially designed slides have chambers of known depth with an etched grid on the chamber bottom
Counting chamber
Counting chambers included in Direct microscopic count
Breed count method, Petroff-Hausser counting chamber, Hemocytometer, and Electronic cell counter
Can be used for counting prokaryotes
Petroff-Hausser counting chamber
Can be used for both prokaryotes and eukaryotes
Hemocytometer
For larger microorganisms (protists and yeast)
Electronic cell counter (Coulter)
A direct method used when quantity of bacteria is very small
Filtration/ Membrane filtration technique
A direct method where a sample is filtered through a thin membrane filter whose pores are too small to allow bacteria to pass the filter
Filtration/ Membrane filtration technique
A thin membrane filter used in Filtration/ Membrane filtration technique
Black polycarbonate membrane filter
A most frequently used direct method of measuring bacterial population
Plate count/ Viable cell count
A direct method that assumes each live bacterium grows and divides to produce one colony
Plate count/ Viable cell count
An advantage to this direct method are:
- measures the number of viable cells
- simple, sensitive, and widely used in food, water, and soil analysis
Plate count/ Viable cell count
Disadvantages to this direct method are:
- low count result if clumps of cells are not broken up
- takes time for visible colonies to form
Plate count/ Viable cell count
The hot agar used in ___ may injure or kill sensitive cells
Pour-plate technique
___ sometimes give higher counts
Spread-plate technique
This technique begins with a sample being pipetted onto surface of agar plate
Spread-plate technique
This technique begins with a sample being pipetted into a sterile plate
Pour-plate technique
A direct method used when the microorganism cannot grow on solid media
Most probable number (MPN) method
This direct method is based on the fact that the greater the number of bacteria in a sample, the more dilution is needed to reduce the density to the point at which no bacteria are left to grow in the tubes in a dilution series
Most probable number (MPN) method
An indirect method measured by spectrophotometer (colorimeter)
Turbidity/ Spectophotometry
An indirect method where as the bacteria multiply in a liquid medium, the medium becomes turbid, or cloudy with cells
Turbidity/ Spectophotometry
An indirect method where when the concentration of bacteria reaches about 10^7 cells per ml, the medium appears slightly cloudy or turbid
Turbidity/ Spectophotometry
An indirect method where they measure the amount of a certain metabolic product
Metabolic Activity
An indirect method used where cells growing in liquid medium are collected by centrifugation, washed, dried in an over, and weighed
Dry Weight
An indirect method used for filamentous organisms
Dry Weight
An indirect method that is not time consuming and not very sensitive
Dry Weight
This direct method is for counting bacteria in milk
Breed Count Method
