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69 Cards in this Set
- Front
- Back
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What is Microbial Growth and what are the basic requirements?
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To increase the amount/number of cells or in mass.
Physical requirements Chemical requirements |
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What are the 3 physical requirements of growth for bacteria?
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Temperature
pH Osmotic pressure |
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What are the 3 cardinal temperatures and explain each of them?
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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 |
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What are the 3 classifications of a species that grow within its optimum temperature (e.g. high, mid, and low).
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Psychrophiles
Mesophiles Thermophiles |
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At what temp can psychrophiles grow and what is its' optimum temp?
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0C to 20C; OPT 15C or lower
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At what temp can mesophiles grow and what is its' optimum temp?
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20C to 40C; OPT 35C to 37C
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At what temp can thermophiles grow and what is its' optimum temp?
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40C and above; OPT 50C (122F)
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At which pH can most bacteria grow around?
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pH 6.5 to pH 7.5
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What classification of pH can a bacteria be categorized when it can grow below pH 4?
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Acidophile
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What is a halophile bateria?
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A bacteria that can tolerate high salt concentrations
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What are the 3 types of solutions that pertains to tonicity and explain each?
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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 |
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In a hypertonic solution, a cell undergoes what?
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Plasmolysis
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What is plasmolysis?
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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.
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What are 4 things that organisms need?
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1. Carbon source
2. Nitrogen 3. Water 4. Other chemical (trace elements, sulfur, and phosphorus) |
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What are the 5 classifications of oxygen requirements?
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Obligate aerobes
Facultative anaerobes Obligate anaerobes Aerotolerant anaerobes Microaerophiles |
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What type of bacteria are obligate aerobes (examples from PP)?
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Mycobacterium tuberculosis
Bacillus |
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What type of bacteria are facultative anaerobes (examples from PP)?
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S. aureus
E. coli |
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What type of bacteria are obligate anaerobes (examples from PP)?
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Clostridium botulimum
Bacteroides |
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Define aerotolerant anaerobe and what type of bacteria are aerotolerant anaerobes (examples from PP)?
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Mircroorganisms that can grow without but can still tolerate the presence of oxygen
Clostridium perfringens Treponema pallidum |
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Define microaerophiles and what type of bacteria are microaerophiles (examples from PP)?
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Microorganism that grow with but can die with an excess amount of oxygen (2%-10& O2).
Helicobater pylori Streptococcus |
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What type of oxygen classification is this under...
In a broth media, there is growth on top only. |
Obligate aerobes
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What type of oxygen classification is this under...
In a broth media, there is growth on the bottom only. |
Obligate anaerobes
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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
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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. |
Microaerophilic
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What type of oxygen classification is this under...
In a broth media, there is growth scattered all throughout the media |
Aerotolerant anaerobe
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What are 4 types of toxic forms of oxygen?
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Singlet oxygen - lowest excited state of dioxygen molecule (O2)
Superoxide - free radical O2- Peroxide anions - H2O2 Hydroxyl radicals - OH |
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What 3 types of enzymes are used against oxygen toxicity?
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Superoxide dismutase
Catalase Peroxidase |
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What is a culture media?
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Any material prepared for the growth of bacteria in a laboratory.
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What is the solidifying agent in a culture medium and where is it derived from?
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Agar - certain algae or seaweed
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What is a chemically defined media and what is it used to grow?
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Exact chemical composition is known
-Fastidious organisms |
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What is a complex media and what type of organisms are grown with this?
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Media in which the exact chemical compositions are unknown but the components are known
- Bacteria & fungi |
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What is used to chemically remove molecular oxygen (O2) that might interfere with the growth of anaerobes?
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Sodium thioglycollate - Reducing agent
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Parasitic and fastidious bacteria must be cultured in what?
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Living animals or cell structures
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What 2 things are used to grow microaerophilic bacteria or other bacteria requiring an increased CO2 concentration?
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Carbon dioxide incubators
Candle jars |
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What are the 3 types of hemolysis and what color do each produce?
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Gamma - No lysis; red color
Alpha - incomplete lysis; green color Beta - Complete lysis; yellow color |
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What are the components of Eosin Methylene Blue (EMB) media?
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Dye -Eosin Y & Methylene blue
Lactose |
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What does the Dyes do in EMB media?
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Inhibit gram (+) growth and distinguish between lactose fermenter & lactose non-fermenter
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What is differential media?
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Media in which allows different bacteria to grow and differentiates between the organisms
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What type of media is blood agar?
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Differential
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What type of media is EMB?
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Selective
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What class of bacteria creates hemolytic properties on blood agar plates (according to the PP)?
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Streptococci
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What are the components to mannitol salt agar?
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High salt concentrations
Mannitol (sugar) Phenol Red indicator |
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What class of bacteria is identified through mannitol salt agar (according to the PP)?
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Staphylococci
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What are the steps to binary fission?
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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 |
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What are the 4 phases of growth?
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Lag Phase
Log Phase Stationary Phase Death Phase |
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What occurs in the lag phase?
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No replication; metabolic activity is high & size of cell increased
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What occurs in the log phase?
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Fastest rate of division under optimum conditions
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What occurs in the stationary phase?
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Equilibrium of division vs death
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What occurs in the death phase?
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Deaths is greater than division
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What is an enriched culture?
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culture in which encourages the growth of a particular microorganism (low concentrations) from a mixed culture
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How method is used to obtain a pure culture?
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Isolation streak plate method
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What is a colony?
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Visible mass of microbial cells that theoretically arose form one cell.
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What are 2 ways to preserve microbes for a long period of time?
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Deep-freezing or lyophilization (freeze-drying)
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What is the normal reproductive method of bacteria and what are 3 other methods used with other specific bacteria?
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1. Binary fission
- Budding - Aerial spore formation - Fragmentation |
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Define generation time.
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The time required for a population to double
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Define logarithmic progression.
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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) |
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What does CFU stand for?
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Colony forming units -
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What 2 DIRECT methods are used to see the number of CFU or plate count?
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Pour plate or Spread plate
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What are 3 DIRECT methods of determining the number of bacteria in a sample?
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Filtration
MPN (most probably number) DMC (direct microscopic count) |
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Explain the pour plate method
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Bacterial dilution is mixed with melted agar and is solidfied; bacteria grow WITHIN medium
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Explain the spread plate method
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Bacterial dilution is spread evenly on top of solidified media; bacteria is grown ON TOP of media
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How is filtration method done?
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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) |
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How is the direct microscopic count done (DMC)?
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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 |
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What is a spectrophotometer used for?
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Used to determine turbidity by measuring the amount of light that passes through a suspension of cells
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What are 2 general ways of counting CFU?
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Direct
Indirect |
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What is turbidity?
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Optical density within a media
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What are 3 INDIRECT methods of estimating bacterial numbers?
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Turbidity
Metabolic activity Dry weight |
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How is metabolic activity used to indirectly estimate bacterial numbers?
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The amount of metabolic end products (e.g. acids or CO2) can correlated with the amount of bacteria.
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What type of organisms are used to indirectly measure dry weight?
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Filamentous organisms & fungi
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