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44 Cards in this Set

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What is a chemotroph?
Phototroph?
-requires the use of a chemical energy source (auto and heterotrophs)
-uses light energy
What do autotrophs utilize?
Heterotrophs?
-inorganic carbon
-organic carbon
What are the four main groups of bacterial nutritional groups?
-photoautotrophs
-photoheterotrophs
-chemoautotrophs
-chemoheterotrophs
What are the two subdivisions of nutritional requirements?
-macronutrients
-micronutrients
What are the major elements of macronutrients?
-C, N, S, K, Mg, Ca, Na, P
-must be supplied in relatively large quantities
What are 7 sources of carbon that may be used by certain bacterial groups?
-carbs
-alcohols
-lipids
-proteins, peptides, and AA
-complex heterocyclic carbon compounds
-petroleium derivatives and hydrocarbons
-carbon dioxide (used only by autotrophic organims)
What are 4 Nitrogen sources for bacteria?
-inorganic forms of N are among the most common (Nh4Cl, NH4, SO4)
-inorganic salts such as KNO3 and KNO2
-atmospheric N can only be used by a few N-fixers
-N from AA is dericed from the breakdown of proteins
What are 4 Sulfur sources for bacteria?
-examples of sulfates supplied as inorganic salts are FeSO4 and CaSO4 *Can be used by most bacteria
-organically bound sulfur is found in the sulfur-containing AA, met, and cys
-H2S
-elemental sulfur rarely used
What are microaerophiles?
-some aerobes sensitive to atmospheric conc. of oxygen
-prefer 2-20% oxygen (not 21)
-must demonstrate sensitivity under all growth conditions
What are facultative anaerobes?
-prefer to grow in the presence of oxygen because they possess cytochromes
-microbes will grow under anaerobic environments IF suitable substitute is available
-can respire oxidatively or fermentatively
*most of lab microbes are facultative anaerobes
Describe anaerobes.
-do not have oxygen linked respiration
-do not possess enzymes to neutralize toxic intermediate products of oxygen metabolism
What are two toxic oxygen-neutralizing enzymes?
-superoxide dismutase
-catalase
What does superoxide dismutase do?
-converts the superoxide radical to a less toxic product, H2O2
-catalase then breaks down H2O2 to molecular oxygen and water OR
-peroxides do the same thing in facultative anaerobes and aerobes that don't have catalase
Why can't anaerobes survive in oxygen?
-they don't have catalase or speroxide dismutase so they can't destroy toxic oxygen intermediates
What are three ways to form anaerobic incubation in the laboratory?
-thioglycollate broth
-anaerobic jar
-glovebox
What are the 4 components of thioglycollate medium?
-glucose as a carbon & energy source
-cysteine and Na thioglycollate as reducing agents
-a small quantity of agar to localize microbes and make bottom of tube anaerobic
-"redox" indicators: Resazurin or Methylene Blue
How do you prepare thioglycollate medium?
-boil semi-solid broth to drive off oxygen, and innoculated while agar is still melted
-tube is mixed using rolling in hands
How does Resazurin and methylene blue react?
-when reduced, both are colorless
-when oxidized, resazurin is red and the other is blue
What are the advantages of thioglycollate medium?
-relatively inexpensive
-easy to transport cultures
What are the disadvantages of thioglycollate medium?
-difficult to obtain a truly oxygen freen environment for very sensitive anaerobes
-microbes are exposed to oxygen during transfers
How do you make a Gas-Pak?
-add water to a pouch of sodium borohydride, citric acid, and sodium bicarbonate
-put envelope in jar, which releases hydrogen and carbon dioxide
-H bonds to oxygen forming water and heat
-add indicator slip if needed such as methylene blue strip
How do you know a Gas-Pak is working properly?
-presence of water droplets
-warmth of jar surface
-color strip turns/stays white
What are the advantages of the anaerobic jar?
-encironment has a lower oxygen concentration than is found in thioglycollate medium
-after jar cost, consumable materials are relatively inexpensive
What are the disatvantages of the anaerobic jar?
-poor seal lets in oxygen
-amount of space is limited
-microbes must be transferred in the presence of oxygen
How does a glove box work?
-a box is accessible through gloves that are impermeable to oxygen
-pump removes all of the air from the box and replaced by an atmosphere of H, CO2, and N
What are the advantages of the glove box?
-more space available
-microbes can be transferred in absence of oxygen
-fresh media can be stored in an oxygen free environment
-less chance for accidental exposure to oxygen
-can grow more oxygen sensitive anaerobes
What are the disadvantages of the glove box?
-takes up more laboratory space
-expensive to purchase
What is a mesophile?
-grow between 25 and 40 degrees celcius
-include most bacteria
*most need to grow around 37 degrees which is body temperature
What is a thermophile?
-thrive at high temperatures
-optimum growth over 50 degrees celcius
What is a psychrophile?
-microorganisms that thrive at lower temperatures
-optimum growth if temperature falls below 15 degrees C
*Psychotroph is term used to describe microbes that grow between 0-30 and are generally responsible for food spoilage
What is a phsychotroph?
-a term used to describe microbes that grow between 0-30 C and are generally responsible for food spoilage
What is an infusion?
-fluids obtained from soaking plant or animal materials that can support microorganism growth
-Can NOT be accurately reproduced
-ex; hay infusion and Brain Heart Infusion
What is a complex?
-usually contain extracts and/or digests of natural products
-unknown composition BUT reproducible
-used for organisms with unknown nutrient requirements for culture maintenance or large-scale cultivations
-ex; nutrient broth, trypticase soy agar, salts broth, etc.
What are some commercially available dehydrated forms?
-peptones: partially digested proteins
-tryptones: partially digested proteins
-casein hydrolysate: digested milk protein
-yeast extract: extract of yeast cells
-beef extract: extracts of beef
What is defined media?
-contain only chemically identified substances in known amounts and can be exactly reproduced
-used to study metabolism, nutrition, genetics, or where absolute control is necessary
-ex; glucose mineral salts medium
What is a minimal defined medium?
-has minimal nutritional requirements for a chemoheterotrophic organism to live on
-bacterium that can grow on these are hardy
What does fastidious mean?
-requires numerous preformed AA and vitamins to live
-extra nutrients added to medium for fastidious microbes
What are microbes that fall between hardy and fastidious known as?
-average
What is the most important ingredient in bacterial medium?
What is it good for?
-water
-it allows minerals to solubilize so they can enter the cell as well as be a chemical reactant for hydrolytic reactions in cell
What are 4 other criteria besides water, that are needed for a medium?
-pH
-Osmotic balance
-Physical form
-Growth factors
Why is pH important for making media?
-controls growth
-most bacteria are slightly acidic (pH6-7)
What does the osmotic balance depend on in a media?
-concentration of ions such as Na, Ca, K, etc.
-proper ion concentration is necessary to maintain osmotic pressure within the cell
What are the different physical forms medium can take?
-broth/liquid
-solid Agar
-semi-solid when only small amount of agar is added to broth
What are some common growth factors used for bacteria in media?
-Vitamins (normal enzymatic activity)
-AA (building blocks of proteins)
-Purines (required for RNA and DNA synthesis)
-Pyrimidines (required for RNA and DNA synthesis)
-Certain lipids