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120 Cards in this Set

  • Front
  • Back
What are the chemical requirements for microbial growth?
Chemical requirements include:

a. water
b. sources of carbon, nitrogen, sulfur, phosphorus
c. Trace elements
d. oxygen
e. organic growth factors
What are the physical requirements for microbial growth?
Physical requirements include:

a. temperature
b. pH
c. osmotic pressure
What are psychrophiles?
cold-loving microbes
What are mesophiles?
moderate-temperature loving
microbes
What are thermophiles?
heat-loving microbes
What is the minimun growth temperature?
is the lowest temperature at which the species will grow.
What is the optimum growth temperature?
is the temperature at which the species grows best
What is the maximum growth temprature?
is the highest temperature at which growth is possible
What temperatures can a psychrophile grow at?
0-20 degrees C, 15 degrees C optimal
Where can psychrophile organisms be found
mainly in the depths of the oceans and in certain Arctic regions.
Why is the refrigerator good for preserving food?
Microbial reproductive rates decrease at low temperatures
Which organisms are responsible for food spoilage at refrigerator temperatures?
Mesophile
Do microbial reproductive rates increase, decrease or stay the same at low temperatures?
decrease
What is the optimum growth temperature of a mesophile?
25-40 degrees C
What type of organisms are mesophiles?
The most common type of microbe

-includes most of the common spoilage and disease organisms.

An organism that grows best in moderate temperature, neither too hot nor too cold,
What is the optimum growth temperature of thermophiles?
50-60 degrees C is Optimal Temp.
What are the growth temperatures of extreme thermophiles?
thermophiles(Archaea) grow at temperatures well above 90oC, near the boiling point of water
What is the minimum growth temperture of thermophiles?
Many are incapable of growth below 45 degrees C
Which organisms (Psychrophiles, mesophiles, or thermophiles) includes most of the common spoilage and disease causing organisms?
Mesophiles
Organisms important in organic compost piles?
? mesophilic bacteria
What pH do most bacteria grow best?
Most bacteria grow best between pH 6.5 and 7.5
What are acidophiles?
include some bacteria which can tolerate acidity.
-Molds
Molds and yeasts grow best at what pH?
pH 5-6
What are some chemical buffers used in bacterial cultures?
peptones, amino acids, phosphates
Why use chemical buffers in bacterial cultures made in labs?
Bacteria cultured in the laboratory will produce acids which can interfere with their growth, therefore, growth media usually contain buffers which will neutralize the acids.
What happens to bacteria that are put into hypertonic solutions?
cause plasmolysis or shrinkage of the cell.
What are extreme halophiles?
require extreme high salt concentrations to live…obligate halophiles Physical
What are facultative halophiles?
do not require high salt concentrations but are able to grow at salt concentrations up to 2% (which inhibits many other bacteria)

-A species of facultative halophiles can tolerate 15% salt.
What are obligate halophiles?
require extreme high salt concentrations to live
What concentration of salt can facultative halophiles grow up to?
up to 2% (which inhibits many other bacteria)
What is the maximum concentration of salt that a species of facultative halophiles tolerate?
15% salt.
What is the concentration of agar used to solidify media?
1.5% salt.
What happens to bacteria that are put into a hypotonic solution?
can cause some bacteria to lyse, especially if the cell wall is weak
What are the chemical requirements for growth?
Water
Carbon
Nitrogen
Sulfur
Phosphorus
Trace Elements
What are the characteristics of water?
???
Know the 4 functions of water covered in lecture 2 (Chapter 2)
Why is water it important for life?
???
Why is carbon important for life?
-is the structural backbone of living matter
-is needed to form all the organic compounds
What is carbon used for?
is needed to form all the organic compounds
Carbon is mostly trapped in which form?
C02 - Carbon Dioxide
What are chemoheterotrophs?
get most of their carbon from their energy source (organic compounds).
What are chemoautotrophs?
derive their carbon from carbon dioxide.

as well as photoautotrophs
What is nitrogen required for?
protein, ATP, DNA and RNA synthesis
What are the sources for nitrogen?
1. decomposing proteins

2. ammonium ions, which are usually found in organic compounds

3. nitrates (NO3)

4. gaseous nitrogen (N2) directly from the atmosphere (i.e. cyanobacteria)
What is nitrogen fixation?
The process by which they absorb nitrogen gas is called
What is symbiosis?
Symbiosis is a close, prolonged association between two (or more) organisms


Symbiotic nitrogen-fixing bacteria, belonging to the genera Rhizobium and Bradyrhizobium are associated with legumes such as clover, soybeans, alfalfa, beans and peas.
What are legumes?
the fruit of certain bean plants.

clover, soybeans, alfalfa, beans and peas.
Why are the genera Rhizobium and Bradyrhizobim important to legumes?
Because they provide the plants with nitrogen.
What is sulfur required for?
1. the synthesis of sulfur-containing amino acids and, thus, protein synthesis

2. vitamin synthesis such as thiamine and biotin
What are the sources for sulfur?
hydrogen sulfide (H2S), sulfate ions (SO4 2-), sulfur-containing amino acids
What is phosphorus required for?
1. nucleic acids
2. ATP
3. phospholipids of cell membranes
What is the source of phosphorus?
phosphate ion (PO43-)
What are trace elements?
Mineral elements that are only required in very small amounts

Most are essential for enzyme activity as cofactors.
Which chemicals are required as cofactors for enzymes?
Trace Elements:

a. iron
b. copper
c. molybdenum
d. zinc
Where is most oxygen found?
found mainly in the atmosphere and little in water (ocean)
Is oxygen present when earth was formed?
No did not exist.
What are aerobes?
microbes that use molecular oxygen

produce more energy from nutrients anaerobes.
What are obligate aerobes?
Requires oxygen to live.
What are facultative anaerobes?
anaerobes can use oxygen when it is present but are able to continue growth using fermentation when oxygen is not available.
What 2 organisms are examples of facultative anaerobes?
E. coli
Yeasts
What are obligate anaerobes and give an example?
Are unable to use molecular oxygen for energy-yielding reactions.
-Most are harmed by oxygen (toxic)
- Example: Clostridium
Why is oxygen toxic to obligate anaerobes?
They are unable to use molecular oxygen for energy-yielding reactions
What are the 4 toxic forms of oxygen?
Singlet Oxygen (O2-)
Superoxide free radicals (O2-)
Peroxide anion (022-)
Hydroxyl free radical (OH)
Which organism is believed to be responsible for initially generating the oxygen for earth’s atmosphere?
???
Singlet Oxygen (O2-)
-is normal molecular 02that has been boosted into a higher energy state and is extremely reactive with other molecules.

-plays a role in the destruction of foreign cells after they areingested by phagocytes
Superoxidefree radicals (O2-)
-are formed in small amounts during the normal respiration of organisms that use oxygen as a final electron acceptor in the electron transport chain.

-Obligate anaerobes such as bacteria of the genus Clostridiumcan also form superoxidefree radicals

-Superoxidefree radicals are very toxic to cellular components because they avidly steal an electron from any neighboring molecule.

-Organisms that grow in atmospheric oxygen must produce an enzyme called superoxidedismutaseto neutralize the superoxidefree radicals to H2O2& O2.
Peroxide anion (O22-)
contained in H2O2

-is very toxic

-There are two enzymes that can neutralize hydrogen peroxide:

a. Catalase: hydrogen peroxide + catalaseproduces water and oxygen bubbles.
2H2O2-----> 2H2O + O2

b. peroxidase: hydrogen peroxide + peroxidaseproduces water
H2O2+ 2 H+
Hydroxyl free radical (OH.)
-the most reactive form of oxygen

-formed in the cytoplasm by ionizing radiation

-produced by a reaction between superoxidefree radicals and peroxide

-Most aerobic respiration produces hydroxyl free radicals, but are transient
What is a way that toxic oxygens are important to body's defense?
Because they are present in the lysosomeof phagocyticcells. Pathogens are killed by exposure to these toxic forms of oxygen.
Which toxic form of oxygen is normal molecular Oxygen that has been boosted into a higher energy state and is extremely reactive with other molecules?
Singlet oxygen
Which toxic form of oxygen plays a role in the destruction of foreign cells after they are ingested by phagocytes?
Singlet Oxygen
Which toxic form of oxygen is very toxic to cellular components because they avidly steals an electron from any neighboring molecule?
Superoxide free radicals
What is superoxide dismutase and what does it do?
Organisms that grow in atmospheric oxygen must produce an enzyme called superoxidedismutaseto neutralize the superoxidefree radicals to H2O2& O2
Which toxic form of oxygen is neutralized by the enzymes catalase and peroxidase?
Peroxide anion (Hydrogen Peroxide??? )
What does catalase do?
neutralize hydrogen peroxide:

hydrogen peroxide + catalaseproduces water and oxygen bubbles.
2H2O2-----> 2H2O + O2
What does peroxidase do?
neutralize hydrogen peroxide:

hydrogen peroxide + peroxidaseproduces water
H2O2+ 2 H+
Which toxic form of oxygen is used as an antimicrobial product?
hydrogen peroxide
benzoyl peroxide
Which toxic form of oxygen is produced by a reaction between superoxide free radicals and peroxide?
Hydroxyl free radical (OH.)
Which toxic form of oxygen is the most reactive form of oxygen?
Hydroxyl free radical
Which toxic form of oxygen is formed in the cytoplasm by ionizing radiation?
Hydroxyl free radical
What is an aerotolerant anaerobe?
can not use oxygen for growth, but tolerate it fairly well.

-possess superoxide dismutase or its equivalent
What is a microaerophile?
are aerobic; require oxygen to grow
Where are they found?
can grow in oxygen concentrations lower than those of air…grow in area little below the surface
What are organic growth factors?
are the essential organic compounds that an organism is unable to synthesize and must obtain directly from the environment.
What are the 3 examples of organic growth factors?
amino acids, purines, and pyrimidines.
What is culture media?
are nutrient materials prepared for the growth of microorganisms in a laboratory.
What is a culture?
microbes that grow and multiply in or on a culture medium.
What is agar and what is it used for?
is a complex polysaccharide derived from marine alga used as a solidifying agent for solid media.
What is a chemically defined media?
must be sterile initially and contain no living microorganisms
what is a slant?
test tubes allowed to solidify with the tube held at an angle so a large surface of growth is available.
What is a deep?
agar which solidifies in a vertical tube.
What is a chemically defined media?
one in which the exact composition is known

-Many growth factors must be provided in the chemically defined medium.
What is a fastidious organism and give an example?
Fastidious organisms are organisms that require many growth factors. (Example: Lactobacillus)
What is a complex media?
culture medium in which the exact composition is not known and varies from batch to batch
What is it composed of ?
- These complex media are made up of nutrients such as extracts from yeasts, beef, or plants or digests of proteins from these and other sources.

- Vitamins and other organic growth factors are provided by meat extracts or yeast extracts.
What is a nutrient broth?
a complex medium in liquid form; made of beef extracts
What is nutrient agar?
a complex medium with agar added
What is a reducing media and give an example?
a culture medium containing ingredients that will remove dissolved oxygen from the medium to allow the growth of anaerobicbacteria.

-Sodium thioglycolateis used in this medium to chemically combine with dissolved oxygen and deplete the oxygen in the culture medium.
What special culture techniques are required to grow Mycobacterium leprae?
Techniques-Some parasitic and fastidious bacteria such as Mycobacteriumleprae(the leprosy bacillus) must be cultured in living animals or in cell cultures. (This organism was once grown on the foot pads of mice, but now is usually grown in armadillos.)
Which organisms need C02 at higher concentrations than atmospheric?
Neisseria gonorrhoeae
Neisseria meningitidis
What is selective media and give an example?
designed to suppress the growth of unwanted bacteria and encourage the growth of the desired microbes.

-Examples: Bismuth sulfite agar is used to isolate the typhoid bacterium, the gram-negative Salmonella typhifrom feces.

-Bismuth sulfite inhibits gram-positive bacteria and most gram-negative bacteria as well.
What is Differential Media and give an example?
A solid culture medium that makes it easier to distinguish colonies of the desired organism from other colonies growing on the same plate.

-Examples: blood agar which contains red blood cells is used to identify bacterial species that destroy red blood cells.

-Streptococcuspyogeneswhich causes strep throat shows a clear ring around the colonies where they have lysedthe red blood cells. (Remember Exp 8)
What is an enrichment culture?
usually a liquid culture medium that provides nutrients and environmental conditions that favor the growth of a particular microbe but are not suitable for the growth of other types of microbes.

-It is designed to increase very low numbers of desired microbes to detectable levels.

-Example: If you want to isolate a microbe capable of growth on phenolfrom a soil sample, use a liquid enrichment medium, with phenol as the only source of C and energy.

-Microbes unable to use phenol will not grow. -Do several transfers into the same type of phenol medium and the bacteria are grown in this media for some time allowing more organisms to grow that can use phenol.
What is a colony?
theoretically arises from a single spore or vegetative cell or from a group of the same microorganism attached to one another in clumps or chains.
What is the most common method used to obtain a pure culture?
Streak plate method
Explain in detail the 3 ways (short- and long- term) to preserve bacterial cultures.
-Short-term storage: refrigeration can be used

-Long-term storage:-Deep-freezingis the process in which a pure culture of microbes is placed in a suspending liquid (glycerol) and quick-frozen at temperatures ranging from -50 to -95oC and stored at -70oC.

-Lyophilization(freeze-drying) involves quick freezing a suspension of microbes at temperatures ranging from -54 to

-72oC and then the water is removedby a high vacuum (sublimation). A powder-like residue containing the microbes can be stored for years.

-The microbes can be revived by hydration with suitable liquid nutrient medium.
What are the 3 methods of reproduction in bacteria?
Binary fission

Fragmentation

Budding
Most bacteria divide by which method?
Binary fission
What are the steps to Binary Fission?
-Steps in binary fission (mitosis & cytokinesis) are:

1. Cell elongation and replication of chromosomal DNA

2. Cell wall and cell membrane grow inward between the two regions of the DNA.

3. Ingrowingcell walls meet

4. Two identical cells are formed

5. Each cell is identical to the parent cell
Describe fragmentation?
a few filamentous species simply fragment and the fragments initiate the growth of new cells.
Describe budding?
in a few species, they form a small initial outgrowth (a bud) that enlarges until it is close to the size ofthe parent cell.
What is the generation time?
is the time required for a cell to divided and its population to double.

-It varies among organisms

-Most bacteria have generation times from 1 to 3 hours.

-Others have generation times of over 24 hours.
Know how to calculate the number of bacteria that are produced after a certain time period.
-1 cell's division produces 2 cells

-2 cells' division produces 4 cells

-3 cells’division produces 8 cells

-The arithmetic number of cells in each generation is expressed as a power of 2 and the exponent tells the number of doubling (generation) that have occurred.

-5 generations would produce 25= 32 cells
2 x 2 x 2 x 2 x 2 = 32

-If E. colihas a generation time of 20 minutes, how many cells would there be after 2 hours?
What are the 4 phases of growth?
Be able to identify the different phases on a graph.
Lag phase

Log or exponential growth phase

Stationary phase

Death, or logarithmic decline phase
What happens during the lag phase?
- This is a period of little or no cell division which occurs initially after you inoculate the new growth medium.

- Cells are not dormant but are undergoing intense metabolic activity, like synthesis of enzymes and various molecules.
What happens during the log phase?
- Cellular reproduction is most active during this period and generation time reaches a constant minimum (a maximum rate of doubling).

- Cells begin to show their visible characteristics: the shape, color, density and groupings of their colonies.

- This is the time when cells are most active metabolically.

- Microorganisms are more sensitive to adverse conditions than they usually are (increased sensitivities to radiation and many antimicrobial drugs).
What happens during the stationary phase?
- A period of equilibrium when the number of microbial deaths balances the number of new cells and the population stabilizes. The metabolic activities of surviving cells also slow at this stage.

- Reasons for the stationary phase probably include the accumulation of waste products that are toxic to cells and the depletion of certain required nutrients.
What happens during the death phase?
-occurs when the number of deaths exceeds the number of new cells formed.

-This occurs until the population is diminished to a tiny fraction of the more resistant cells, or the population may die out entirely.
What are the 2 direct methods of measuring microbial growth?
Direct microscopic count
What are the advantages and disadvantages of the plate count method?
?
Know how to calculate the serial dilution problems that we went over in lecture. Know how to do/explain a serial dilution.
?