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33 Cards in this Set
- Front
- Back
microbial growth
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increase in number of cells, not size
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Temperature requirements for growth
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psychrophiles: cold loving
psychrotrophs: food spoilage mesophiles: moderate temperature loving thermophiles: heat loving hyperthermophiles: archea |
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PH requirements for growth
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-Most bacteria grow between pH 6.5 and 7.5
-Molds and yeasts grow between pH 5 and 6 -Acidophiles grow in acidic environments |
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Osmotic Pressure
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-Hypertonic environments, increase salt or sugar, cause plasmolysis
-Extreme or obligate halophiles require high osmotic pressure -Facultative halophiles tolerate high osmotic pressure |
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Carbon sources
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Autotrophs- CO2 sole or principal biosynthetic carbon source
Heterotrophs- Reduced, preformed, organi molecules from other organisms |
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Energy sources
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Phototrophs- Light
Chemotrophs- Oxidation of organic or inorganic compounds |
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Electron sources
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Lithotrophs- Reduced inorganic molecules
Organotrophs- Organic molecules |
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Chemical requirements for growth
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carbon, nitrogen, sulfur, phosphorus, trace elements, organic growth factors, oxygen
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Carbon
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structural organic molecules, energy source
-chemotrophs use organic carbon sources -autotrophs use CO2 |
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Nitrogen
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In amino acids, proteins
-Most bacteria decompose proteins -Some bacteris use NH4+ or NO3- -A few bacteria use N2 in nitrogen fixation |
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Sulfur
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In amino acids, thiamine, biotin
-Most bacteria decompose proteins -Some bacteria use SO4^2 or H2S |
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Phosphorus
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In DNA, RNA, ATP, and membranes
- PO4^3- is a source of phosphorus |
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Trace elements
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inorganic elements required in small amounts
-usually as enzyme cofactors |
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Organic growth factors
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organic compounds obtained from the environment
-vitamins, amino acids, purines, pyrimidines |
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Oxygen
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obligate aerobes; faultative anaerobes; obligate anaerobes; aerotolerant anaerobes; microaerophiles
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Toxic forms of oxygen
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singlet oxygen, superoxide free radicals, peroxide anion, hydroxyl radical
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culture medium
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nutrients prepared for microbial growth
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sterile
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no living microbes
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inoculum
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introduction of microbes into medium
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culture
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microbes growing in/on culture medium
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Agar
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complex polysaccharide
-Used as solidifying agent for culture media in petri plates, slants, and deeps -generally not metabolized by microbes -liquifies at 100 degrees C -solidifies ~ 40 degrees C |
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Chemically defined media
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exact chemical composition is known
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complex media
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extracts and digests of yeasts, meat, or plants.
eg Nutrient broth; nutrient agar |
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Anaerobic Culture Methods
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-Reducing media: contain chemicals (thioglycollate or oxyrase) that combine O2--heated to drive off O2
-Anaerobic jar -Anaerobic chamber -Capnophiles require CO2, Candle jar, CO2-packet |
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Selective media
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supress unwanted microbes and encouage desired microbes
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differential media
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make it easy to distinguish colonies of different microbes
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enrichment media
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encourages growth of desired microbe
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pure culture
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contains only one species or strain
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colony
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a population of cells arising from a single cell or spore or from a group of attached cells
-often called a colony-forming unit (CFU) |
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Preserving bacteria cultures
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deep freezing: -50 to -95 degrees C
lyophilization (freeze drying): Frozen (-54 to -72C) and dehydrated in a vacuum |
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Reproduction in prokaryotes
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binary fission, budding, conidiospores (actinomycetes), fragmentation of filaments
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Direct measurements of microbial growth
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-plate counts: perform serial dilutions of a sample. Filtration.
-multiple tube MPN test: count positive tubes and compare to statistical MPN table -Direct Microscopic Count |
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Estimating Bacterial numbers by Indirect Methods
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Turbidity; metabolic activity; dry weight
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