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44 Cards in this Set
- Front
- Back
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What is a chemotroph?
Phototroph? |
-requires the use of a chemical energy source (auto and heterotrophs)
-uses light energy |
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What do autotrophs utilize?
Heterotrophs? |
-inorganic carbon
-organic carbon |
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What are the four main groups of bacterial nutritional groups?
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-photoautotrophs
-photoheterotrophs -chemoautotrophs -chemoheterotrophs |
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What are the two subdivisions of nutritional requirements?
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-macronutrients
-micronutrients |
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What are the major elements of macronutrients?
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-C, N, S, K, Mg, Ca, Na, P
-must be supplied in relatively large quantities |
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What are 7 sources of carbon that may be used by certain bacterial groups?
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-carbs
-alcohols -lipids -proteins, peptides, and AA -complex heterocyclic carbon compounds -petroleium derivatives and hydrocarbons -carbon dioxide (used only by autotrophic organims) |
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What are 4 Nitrogen sources for bacteria?
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-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 |
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What are 4 Sulfur sources for bacteria?
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-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 |
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What are microaerophiles?
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-some aerobes sensitive to atmospheric conc. of oxygen
-prefer 2-20% oxygen (not 21) -must demonstrate sensitivity under all growth conditions |
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What are facultative anaerobes?
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-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 |
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Describe anaerobes.
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-do not have oxygen linked respiration
-do not possess enzymes to neutralize toxic intermediate products of oxygen metabolism |
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What are two toxic oxygen-neutralizing enzymes?
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-superoxide dismutase
-catalase |
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What does superoxide dismutase do?
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-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 |
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Why can't anaerobes survive in oxygen?
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-they don't have catalase or speroxide dismutase so they can't destroy toxic oxygen intermediates
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What are three ways to form anaerobic incubation in the laboratory?
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-thioglycollate broth
-anaerobic jar -glovebox |
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What are the 4 components of thioglycollate medium?
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-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 |
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How do you prepare thioglycollate medium?
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-boil semi-solid broth to drive off oxygen, and innoculated while agar is still melted
-tube is mixed using rolling in hands |
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How does Resazurin and methylene blue react?
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-when reduced, both are colorless
-when oxidized, resazurin is red and the other is blue |
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What are the advantages of thioglycollate medium?
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-relatively inexpensive
-easy to transport cultures |
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What are the disadvantages of thioglycollate medium?
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-difficult to obtain a truly oxygen freen environment for very sensitive anaerobes
-microbes are exposed to oxygen during transfers |
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How do you make a Gas-Pak?
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-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 |
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How do you know a Gas-Pak is working properly?
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-presence of water droplets
-warmth of jar surface -color strip turns/stays white |
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What are the advantages of the anaerobic jar?
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-encironment has a lower oxygen concentration than is found in thioglycollate medium
-after jar cost, consumable materials are relatively inexpensive |
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What are the disatvantages of the anaerobic jar?
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-poor seal lets in oxygen
-amount of space is limited -microbes must be transferred in the presence of oxygen |
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How does a glove box work?
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-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 |
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What are the advantages of the glove box?
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-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 |
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What are the disadvantages of the glove box?
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-takes up more laboratory space
-expensive to purchase |
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What is a mesophile?
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-grow between 25 and 40 degrees celcius
-include most bacteria *most need to grow around 37 degrees which is body temperature |
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What is a thermophile?
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-thrive at high temperatures
-optimum growth over 50 degrees celcius |
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What is a psychrophile?
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-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 |
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What is a phsychotroph?
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-a term used to describe microbes that grow between 0-30 C and are generally responsible for food spoilage
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What is an infusion?
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-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 |
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What is a complex?
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-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. |
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What are some commercially available dehydrated forms?
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-peptones: partially digested proteins
-tryptones: partially digested proteins -casein hydrolysate: digested milk protein -yeast extract: extract of yeast cells -beef extract: extracts of beef |
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What is defined media?
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-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 |
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What is a minimal defined medium?
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-has minimal nutritional requirements for a chemoheterotrophic organism to live on
-bacterium that can grow on these are hardy |
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What does fastidious mean?
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-requires numerous preformed AA and vitamins to live
-extra nutrients added to medium for fastidious microbes |
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What are microbes that fall between hardy and fastidious known as?
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-average
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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 |
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What are 4 other criteria besides water, that are needed for a medium?
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-pH
-Osmotic balance -Physical form -Growth factors |
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Why is pH important for making media?
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-controls growth
-most bacteria are slightly acidic (pH6-7) |
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What does the osmotic balance depend on in a media?
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-concentration of ions such as Na, Ca, K, etc.
-proper ion concentration is necessary to maintain osmotic pressure within the cell |
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What are the different physical forms medium can take?
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-broth/liquid
-solid Agar -semi-solid when only small amount of agar is added to broth |
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What are some common growth factors used for bacteria in media?
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-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 |
