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What are the 2 things organisms require?
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What are the metabolic options for acquiring carbon?
- Autotrophs- use inorganic carbon as their carbon source
- Heterotrophs- require organic compounds as their carbon source
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What are autotrophs?
Use inorganic carbon as their carbon source
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What is important when growing autotrophs in the lab?
Dont need a medium with carbon because it will use CO2 from the air
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What are heterotrophs?
Require organic compounds as their carbon source
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What are the 4 trophic groups?
- Photoautotrophs- light for energy, CO2 for carbon
- Photoheterotrophs- light for energy, organic compounds for carbon
- Chemoautotrophs- chemical compounds for energy, CO2 for carbon
- Chemoheterotrophs- chemicals for energy, organic compounds for CO2
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What is the most common trophic group in food microbiology?
Chemoheterotrophs
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What are macronutrients?
- Required in large amounts
- Found in organic and inorganic molecules
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What are the main macronutrients?
- Phosphorus
- Sulfur
- Potassium
- Magnesium
- Calcium
- Iron
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What is the role of phosphorus?
Nucleic acids and phospholipids
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What is the role of sulphur?
Amino acids (methionine, cysteine) vitamins
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What is the role of potassium?
Enzyme activity
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What is the role of magnesium?
Stabilizes ribosomes, membranes, nucleic acids, enzyme activity
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What is the role of calcium?
Stabilizes cell walls, heat stability of bacterial endospores
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What is the role of iron?
Plays a key role in energy acquisition (enzymes)
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What are the principles of micronutrients?
- Required in trace amounts
- Usually metals
- Usually play a role in enzymes
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What are the principle characteristics of growth factors?
- Required in trace amounts
- Most commonly found in vitamins (as coenzymes)
- Also amino acids, purine, pyrimidines
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What is the definition of culture media?
Nutrient recipe used to grow microorganisms in the laboratory
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What are the 3 categories of culture media?
- Defined or complex
- Selective or differential
- Liquid or solid
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What is a defined media?
- Prepared by adding precise amount of purified chemicals to purified water
- Exact chemical composition is known
- Carbon source is of paramount importance
- Usually one carbon source
- Nature and concentration depend on the microorganism to be cultivated
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What is a complex media?
- For growing fastidious method
- Knowledge of the exact composition is not essential
- Employ digests of animal, plant or microbial products
- Impure, but highly nutritions substances
- Rich, undefined composition
- Reduced control over its composition
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What is selective or differential media?
Some culture media are made to be selective or differential or both
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What is selective media?
Contain compounds that selectively inhibit many microorganisms but not specific ones
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What is differential media?
- Contain an indicator (typically a dye) that visually shows a biochemical reaction
- Useful for distinguishing between species of bacteria
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What are the 4 phases of bacterial growth?
- Lag phase
- Exponential phase
- Stationary phase
- Death phase
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What happens during the lag phase of bacterial growth?
- No growth occurs
- Time required for synthesis of appropriate, depleted, or damaged cellular constituents
- Variable duration (growth conditions, state of inoculum)
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What is generation time, in reference to bacterial growth?
- Time required for a cell number and mass to double
- Bacteria< fungi, protozoa
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What can cause variations in generation time?
- Varies among species depending on genetic factors (metabolic capabilities)
- Varies within species depending on environmental factors (nutrients available, temp, O2, pH)
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What are some factors that limit the growth of the population during the stationary phase?
- Essential nutrients of the culture medium are depleted
- Metabolic byproducts accumulate in the medium and inhibit growth
- Other conditions become inadequate (temp, O2, pH etc)
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What is the stationary phase of cell growth?
No net increase or decrease in cell numbers
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What is cryptic growth during the stationary phase?
- Cell functions continue
- Energy metabolism and biosynthesis
- Some cells divide, some cells die = balance
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What is the most important factor affecting growth and survival of microorganisms?
Termperature
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What happens if temperature is too low?
Inhibits growth
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What happens if temperature is too high?
Cell death
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What are the cardinal temperatures?
Minimum, optimum and maximum temperatures at which a species can grow
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What does water activity depend on?
- Water content
- Concentration of solutes
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What are nonhalophiles?
- Microorganism unable to cope with a low water activity
- Become dehydrated and dormant, or die
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What are halotolerants?
- Can tolerate some reduction in water activity
- Grow best in the absence of the added solute
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What are halophiles?
- Have a specific requirement for NaCl
- Grow optimally at reduced water activity
- Optimal NaCl concentration and water activity varies with species
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What are mid halophiles?
- Require 1-6% NaCl
- Seawater ~3% NaCl
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What are moderate halophiles?
Require 7-14% NaCl
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What are extreme halophiles?
Require 15-30% NaCl
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What are osmophiles?
Able to live in environments high in sugar content
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What are Xenophiles?
- Able to grow in very dry environments
- Made by lack of water rather than from dissolved solutes
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What does 'strepto' mean?
Chain of something
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What does 'staph-' mean?
A group that is not very organized
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What is a bacterial endospore?
- Produced by some gram-positive bacteria as a survival strategy
- Contains protected essential cellular constituents
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What are flagella
Filamentous structures composed of many composed of many copies of a protein called flagellin
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What are the roles of extracellular polysaccharides secreted by some bacteria?
- Assist in the attachment of microorganisms to solid surfaces
- Make microorganisms more difficult to eliminate by phagocytic cells, antibiotics, and antimicrobials
- Bind significant amounts of water- may play some role in resistance to dessiccation
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What are some types of extracellular polysaccharides?
- Slime layers- Flexible, thin, loosely attached to the cell
- Capsules- Rigid, thick, firmly attached to the cell
- Biofilms- Numerous and diverse microorganisms embedded in a matrix
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What are some characteristics of yeast?
- Unicellular
- Reproduce by budding division
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What are some characteristics of moulds?
- Are multicellular
- Form a network of long, branched, tubular filaments (hypha, or hyphae)
- Hyphae grow together to form a compact tuft (mycelium or mycelia)
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What are the characteristics of protozoa?
- Unicellular
- Grouping based on mode of locomotion (amoebae, ciliates, flagellates, apicomplexans- typically nonmotile)
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What are helminths?
- Macroscopic, multicellular, worms
- Found throughout the natural world
- Some in parasitic associations with animals
- Life cycles are complex (include more than one host, include different forms)
- Include cestodes, trematodes, nematodes
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Are viruses living?
No, they are nonliving
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What are viruses?
Genetic elements that cannot replicate independently of a living cell (host cell)
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What is the most numerous microorganism on earth?
viruses
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What types of cells can viruses infect?
Can specifically infect all types of cells
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What makes up prions?
Consists entirely of proteins (no DNA, no RNA)
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How are prions synthesized?
Synthesized by neurons (mainly in the brain) of all mammals
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What is the difference between a normal prion and a pathogenic prion?
Same amino acid sequence, but different conformation
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How does pH effect microbial growth?
- Can add a buffer to maintain pH
- Add an indicator dye to evaluate any change
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What is osmosis?
Water diffusing from regions of low solute concentration to regions of high solute concentration
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What do reductants do?
Tend to give electrons
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What do oxidants do?
Tend to accept electrons
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