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What are the 2 things organisms require?
What are the metabolic options for acquiring carbon?
- Autotrophs- use inorganic carbon as their carbon source
- Heterotrophs- require organic compounds as their carbon source
What are autotrophs?
Use inorganic carbon as their carbon source
What is important when growing autotrophs in the lab?
Dont need a medium with carbon because it will use CO2 from the air
What are heterotrophs?
Require organic compounds as their carbon source
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
What is the most common trophic group in food microbiology?
What are macronutrients?
- Required in large amounts
- Found in organic and inorganic molecules
What are the main macronutrients?
What is the role of phosphorus?
Nucleic acids and phospholipids
What is the role of sulphur?
Amino acids (methionine, cysteine) vitamins
What is the role of potassium?
What is the role of magnesium?
Stabilizes ribosomes, membranes, nucleic acids, enzyme activity
What is the role of calcium?
Stabilizes cell walls, heat stability of bacterial endospores
What is the role of iron?
Plays a key role in energy acquisition (enzymes)
What are the principles of micronutrients?
- Required in trace amounts
- Usually metals
- Usually play a role in enzymes
What are the principle characteristics of growth factors?
- Required in trace amounts
- Most commonly found in vitamins (as coenzymes)
- Also amino acids, purine, pyrimidines
What is the definition of culture media?
Nutrient recipe used to grow microorganisms in the laboratory
What are the 3 categories of culture media?
- Defined or complex
- Selective or differential
- Liquid or solid
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
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
What is selective or differential media?
Some culture media are made to be selective or differential or both
What is selective media?
Contain compounds that selectively inhibit many microorganisms but not specific ones
What is differential media?
- Contain an indicator (typically a dye) that visually shows a biochemical reaction
- Useful for distinguishing between species of bacteria
What are the 4 phases of bacterial growth?
- Lag phase
- Exponential phase
- Stationary phase
- Death phase
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)
What is generation time, in reference to bacterial growth?
- Time required for a cell number and mass to double
- Bacteria< fungi, protozoa
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)
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)
What is the stationary phase of cell growth?
No net increase or decrease in cell numbers
What is cryptic growth during the stationary phase?
- Cell functions continue
- Energy metabolism and biosynthesis
- Some cells divide, some cells die = balance
What is the most important factor affecting growth and survival of microorganisms?
What happens if temperature is too low?
What happens if temperature is too high?
What are the cardinal temperatures?
Minimum, optimum and maximum temperatures at which a species can grow
What does water activity depend on?
- Water content
- Concentration of solutes
What are nonhalophiles?
- Microorganism unable to cope with a low water activity
- Become dehydrated and dormant, or die
What are halotolerants?
- Can tolerate some reduction in water activity
- Grow best in the absence of the added solute
What are halophiles?
- Have a specific requirement for NaCl
- Grow optimally at reduced water activity
- Optimal NaCl concentration and water activity varies with species
What are mid halophiles?
- Require 1-6% NaCl
- Seawater ~3% NaCl
What are moderate halophiles?
Require 7-14% NaCl
What are extreme halophiles?
Require 15-30% NaCl
What are osmophiles?
Able to live in environments high in sugar content
What are Xenophiles?
- Able to grow in very dry environments
- Made by lack of water rather than from dissolved solutes
What does 'strepto' mean?
Chain of something
What does 'staph-' mean?
A group that is not very organized
What is a bacterial endospore?
- Produced by some gram-positive bacteria as a survival strategy
- Contains protected essential cellular constituents
What are flagella
Filamentous structures composed of many composed of many copies of a protein called flagellin
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
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
What are some characteristics of yeast?
- Reproduce by budding division
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)
What are the characteristics of protozoa?
- Grouping based on mode of locomotion (amoebae, ciliates, flagellates, apicomplexans- typically nonmotile)
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
Are viruses living?
No, they are nonliving
What are viruses?
Genetic elements that cannot replicate independently of a living cell (host cell)
What is the most numerous microorganism on earth?
What types of cells can viruses infect?
Can specifically infect all types of cells
What makes up prions?
Consists entirely of proteins (no DNA, no RNA)
How are prions synthesized?
Synthesized by neurons (mainly in the brain) of all mammals
What is the difference between a normal prion and a pathogenic prion?
Same amino acid sequence, but different conformation
How does pH effect microbial growth?
- Can add a buffer to maintain pH
- Add an indicator dye to evaluate any change
What is osmosis?
Water diffusing from regions of low solute concentration to regions of high solute concentration
What do reductants do?
Tend to give electrons
What do oxidants do?
Tend to accept electrons