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44 Cards in this Set

  • Front
  • Back
What is a chemotroph?
-requires the use of a chemical energy source (auto and heterotrophs)
-uses light energy
What do autotrophs utilize?
-inorganic carbon
-organic carbon
What are the four main groups of bacterial nutritional groups?
What are the two subdivisions of nutritional requirements?
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?
-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
-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
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
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?
What is the most important ingredient in bacterial medium?
What is it good for?
-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?
-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?
-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