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69 Cards in this Set

  • Front
  • Back
What is Microbial Growth and what are the basic requirements?
To increase the amount/number of cells or in mass.

Physical requirements
Chemical requirements
What are the 3 physical requirements of growth for bacteria?
Osmotic pressure
What are the 3 cardinal temperatures and explain each of them?
Minimum growth temperature - Lowest temp at which a species will grow

Optimum growth temperature - Temp in which a species will grow best (fastest)

Maximum growth temperature - Highest temp at which growth is possible
What are the 3 classifications of a species that grow within its optimum temperature (e.g. high, mid, and low).
At what temp can psychrophiles grow and what is its' optimum temp?
0C to 20C; OPT 15C or lower
At what temp can mesophiles grow and what is its' optimum temp?
20C to 40C; OPT 35C to 37C
At what temp can thermophiles grow and what is its' optimum temp?
40C and above; OPT 50C (122F)
At which pH can most bacteria grow around?
pH 6.5 to pH 7.5
What classification of pH can a bacteria be categorized when it can grow below pH 4?
What is a halophile bateria?
A bacteria that can tolerate high salt concentrations
What are the 3 types of solutions that pertains to tonicity and explain each?
Isotonic solution - Solution has the same concentration as the cell

Hypertonic solution - Solution concentration is higher vs. cell concentration

Hypotonic solution - Solution concentration is lower vs. cell concentration
In a hypertonic solution, a cell undergoes what?
What is plasmolysis?
When the cell is in a hypertonic solution and water is driven out of the cell; this creates the cell to shrink and plasma membrane separates itself from cell wall.
What are 4 things that organisms need?
1. Carbon source
2. Nitrogen
3. Water
4. Other chemical (trace elements, sulfur, and phosphorus)
What are the 5 classifications of oxygen requirements?
Obligate aerobes
Facultative anaerobes
Obligate anaerobes
Aerotolerant anaerobes
What type of bacteria are obligate aerobes (examples from PP)?
Mycobacterium tuberculosis
What type of bacteria are facultative anaerobes (examples from PP)?
S. aureus
E. coli
What type of bacteria are obligate anaerobes (examples from PP)?
Clostridium botulimum
Define aerotolerant anaerobe and what type of bacteria are aerotolerant anaerobes (examples from PP)?
Mircroorganisms that can grow without but can still tolerate the presence of oxygen

Clostridium perfringens
Treponema pallidum
Define microaerophiles and what type of bacteria are microaerophiles (examples from PP)?
Microorganism that grow with but can die with an excess amount of oxygen (2%-10& O2).

Helicobater pylori
What type of oxygen classification is this under...

In a broth media, there is growth on top only.
Obligate aerobes
What type of oxygen classification is this under...

In a broth media, there is growth on the bottom only.
Obligate anaerobes
What type of oxygen classification is this under...

In a broth media, there is growth mostly on top with a scattered growth throughout the media
Facultative anaerobes
What type of oxygen classification is this under...

In a broth media, there is growth directly right below the surface line of the media, but not on the surface.
What type of oxygen classification is this under...

In a broth media, there is growth scattered all throughout the media
Aerotolerant anaerobe
What are 4 types of toxic forms of oxygen?
Singlet oxygen - lowest excited state of dioxygen molecule (O2)

Superoxide - free radical O2-

Peroxide anions - H2O2

Hydroxyl radicals - OH
What 3 types of enzymes are used against oxygen toxicity?
Superoxide dismutase


What is a culture media?
Any material prepared for the growth of bacteria in a laboratory.
What is the solidifying agent in a culture medium and where is it derived from?
Agar - certain algae or seaweed
What is a chemically defined media and what is it used to grow?
Exact chemical composition is known

-Fastidious organisms
What is a complex media and what type of organisms are grown with this?
Media in which the exact chemical compositions are unknown but the components are known

- Bacteria & fungi
What is used to chemically remove molecular oxygen (O2) that might interfere with the growth of anaerobes?
Sodium thioglycollate - Reducing agent
Parasitic and fastidious bacteria must be cultured in what?
Living animals or cell structures
What 2 things are used to grow microaerophilic bacteria or other bacteria requiring an increased CO2 concentration?
Carbon dioxide incubators
Candle jars
What are the 3 types of hemolysis and what color do each produce?
Gamma - No lysis; red color
Alpha - incomplete lysis; green color
Beta - Complete lysis; yellow color
What are the components of Eosin Methylene Blue (EMB) media?
Dye -Eosin Y & Methylene blue

What does the Dyes do in EMB media?
Inhibit gram (+) growth and distinguish between lactose fermenter & lactose non-fermenter
What is differential media?
Media in which allows different bacteria to grow and differentiates between the organisms
What type of media is blood agar?
What type of media is EMB?
What class of bacteria creates hemolytic properties on blood agar plates (according to the PP)?
What are the components to mannitol salt agar?
High salt concentrations
Mannitol (sugar)
Phenol Red indicator
What class of bacteria is identified through mannitol salt agar (according to the PP)?
What are the steps to binary fission?
1. Cell elongates and DNA is replaced
2. Cell wall and plasma membrane begin to divide
3. Cross-wall forms completely around divided DNA
4. Cell separates
What are the 4 phases of growth?
Lag Phase
Log Phase
Stationary Phase
Death Phase
What occurs in the lag phase?
No replication; metabolic activity is high & size of cell increased
What occurs in the log phase?
Fastest rate of division under optimum conditions
What occurs in the stationary phase?
Equilibrium of division vs death
What occurs in the death phase?
Deaths is greater than division
What is an enriched culture?
culture in which encourages the growth of a particular microorganism (low concentrations) from a mixed culture
How method is used to obtain a pure culture?
Isolation streak plate method
What is a colony?
Visible mass of microbial cells that theoretically arose form one cell.
What are 2 ways to preserve microbes for a long period of time?
Deep-freezing or lyophilization (freeze-drying)
What is the normal reproductive method of bacteria and what are 3 other methods used with other specific bacteria?
1. Binary fission

- Budding
- Aerial spore formation
- Fragmentation
Define generation time.
The time required for a population to double
Define logarithmic progression.
A logarithmic representation of bacterial division of 2 to the "n"th power, where n = number of generations.

Example: 2 cells, 4 cells, 8, 16, 32, 65, etc)
What does CFU stand for?
Colony forming units -
What 2 DIRECT methods are used to see the number of CFU or plate count?
Pour plate or Spread plate
What are 3 DIRECT methods of determining the number of bacteria in a sample?
MPN (most probably number)
DMC (direct microscopic count)
Explain the pour plate method
Bacterial dilution is mixed with melted agar and is solidfied; bacteria grow WITHIN medium
Explain the spread plate method
Bacterial dilution is spread evenly on top of solidified media; bacteria is grown ON TOP of media
How is filtration method done?
A certain amount/sample of dilution is taken and "filtered" through a membrane filter. The sample is then transferred to a culture media and grown to be counted.

Example: can be used to count amount of bacteria in a small water mass (e.g. lake)
How is the direct microscopic count done (DMC)?
A sample is take from a certain product and is smeared onto a slide. It is then stained to count the amount of bacteria within a certain area.

Example: Milk; .001 mL is taken and bacteria is 100 singlel bateria is counted over a square centimeter. This indicated that there is 100B/.001ML
What is a spectrophotometer used for?
Used to determine turbidity by measuring the amount of light that passes through a suspension of cells
What are 2 general ways of counting CFU?
What is turbidity?
Optical density within a media
What are 3 INDIRECT methods of estimating bacterial numbers?
Metabolic activity
Dry weight
How is metabolic activity used to indirectly estimate bacterial numbers?
The amount of metabolic end products (e.g. acids or CO2) can correlated with the amount of bacteria.
What type of organisms are used to indirectly measure dry weight?
Filamentous organisms & fungi