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95 Cards in this Set
- Front
- Back
Physical requirements for microbial growth?
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Temperature: Minimum, Optimum and Maximum.
pH: Osmotic pressure: |
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Acidophiles grow in ________ environment.
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Acidic
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Most bacteria grow between pH of ___ and ___.
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6.5 to 7.5
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Molds and yeast grow between pH of ___ and ___
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5 - 6
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Plasmolysis
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shrinking of the cell's cytoplasm
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What causes plasmolysis?
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Hypertonic environments, the increase in salt or sugar.
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Extreme or obligate halophiles require?
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High osmotic pressure and salt. Eg. Dead Sea. (30% salt environment)
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Faculative halophiles tolerate?
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High osmotic pressure. (2% salt environment)
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Chemicals required in microbial growth
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Nitrogen
Sulfur Phosphorus Carbon Trace elements (inorganic required in small amounts) |
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Nitrogen is found in?
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Amino acids, proteins
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Most bacteria decompose
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proteins
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Some bacteria use
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NH4+ andNO3-
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Sulfur is found
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in amino acids, thiamine, biotin
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Phosphorus is found in
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DNA, RNA, ATP and membranes
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PO4 3- is a source of _____.
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Phosphorus
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Trace elements
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inorganic elements required in small amounts. They are usually enzyme co factors: Iron, copper, zinc.
Naturally present in tap water. |
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Carbon is a
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structural organic molecule, energy source
Chemoheterotrophs use organic carbon sources Autotrophs use CO2. |
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Mesophelics
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cause infection in warm blooded animals eg. humans
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Endospores may survive usual ________
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heat treatments. Eg. canning
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Most bactaria can withstand slight changes in ________ pressure
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osmotic
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Hypertonic environments
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increase salt or sugar, and cause plasmolysis. (water out of the cell)
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Extreme or obligate halophiles regire
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HIGH osmotic pressure
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Isotonic solution is ____________%NaCl
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0.85-0.9 %NaCl
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Hypertonic sloution is ______%Nacl
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10%
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Obligate anaerobes
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No oxygen, LACK ENZYMES. Grow in deep wounds with O2.
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Facultative anaerobes are
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both aerobic and anaerobic but BETTER IN O2 for growth.
They HAVE the enzymes. |
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Aerotolerant anaerobes
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only grow anaerobically but continue in presence of O2
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Micro aerophilic
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O2 is reqired in low concentration
NO ENZYMES |
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Aerobes need O2 as a final
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(e-) exceptor in electron transport pathway but toxic chemical and free radicals are produced. However, aerobes have enzymes to handle them.
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Catalase enzyme
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ID bacteria as catalase + or -
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Peroxidese enzyme and superoxide dismotase (SOD)
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break down superoxide free radicals (O2-)
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Organic growth factors
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vitamins, amino acids, purines and pyrimidines
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Culture medium
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nutrients are prepared for microbial growht. Has to be sterile before exposure.
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Inoculum
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introduction of microbes in to medium
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Culture
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Microbes growing in/on culture medium
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Complex polysaccharide
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derivative from alge and used used as solidifying agent for culture medai in Petri dishes, slants and deeps in lab.
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Generally not metabolized by microbes
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complex polysaccharides
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Liqefies at 100 degrees celsius
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agar
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Agar solidifies at _______ degrees celsius
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-40
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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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Exactract and digest of yeasts, meat or plants.
Nutrient broth (soup) Nutrient agar |
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Fastidious microbes
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Require many growth factors Eg. Lactobacilus
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Short chains of amino acids are digested by _______ ________
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most bacteria
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Reducing media
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Contains chemicals tioglycollate or oxyrase, that combine with O2 and drive it off
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Selective media
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supresses unwanted microbes and encourages disered microbes. Eg. Streptococus and not any other bacteria.
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Eosin Methylene Blue (EMB)
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isolated gram -ve coliforms
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Coli-type colonies are very ____ color.
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dark eg. lactose +
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Aerogenes-type colonies are less _______ color.
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dark eg. lactose -
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Differential media
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Makes it easier to distinguish colonies of desired organism
Eg. Tellurite-Glycine Agar: completly inhibits growth of coaguase-negative staphylococci |
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Coagulase
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is an enzyme produced by staphloccoccus aureus that converts fibrogen to fibrin.
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Potassium tellurate
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Differential agent in the differential medium.
Coagulase-positive staphylococcus reduce tellurite produces black colonies. |
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Media can be both ________ and _________.
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Differential and Selective
Eg. Mannitol ssalt agar. High salt selects for S. aureus and mannitol fermentation differentiates them from non-mannitol fermenting bacteria. |
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Enrichment Media
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Encourages growth of desired microbe.
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A pure culture
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contains only ONE SPECIES or STRAIN
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A colony
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is a population of cells arising from a singele cell or spore or from group of attached cells.
There is trillions of microorganisms in a colony. |
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CFU
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Colony is often called "colony forming unit"
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Defferental meadia make it easier to
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distinguish colonies of desired organisms from other colonies.
Eg. red blood cells (sheep), certain kind of bacteria produce hemolysis on the plate. |
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Manitol Salt Agar
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Salty medium has ptt indicator dye which changes color red to yellow if media mennitol is fermented.
Eg. Strep. Aureus (Pathogenic), Staph Epidermidis (Non-pathogenic) |
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MacConkeg's Agar
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Both selective and differential. Bilesalts and crystal violet inhibits growth of G+ bacteria. It encourages lactose fermentors
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Selective Media
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suppresses growth of unwanted bacteria but encourages growth of desired ones.
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Sabourd's Media
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Dextraose with pH5.6 to isolate fungi that outgrow most bacteria.
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Dies such as brilliant green inhibit
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gram (+)ve bacteria.
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Preserving bacterial culture is done by:
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Deep freezing: -50 - -90 degreees celsius and
Lyophilization: freeze-drying |
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Lyophilization
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freeze-drying. Bacteria are frozen at (-54)-(-95) degrees celsius and dehydrated in a vacuum (sublimation)
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Sublimation
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Dehydrating of bacteria in a vacum
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Preserved residue containing surviving microbes can be revived by __________ yealrs later.
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hydration
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Prokaryote ways of reproduction
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Binary fussion
Budding Conidiospores (actinomycetes) Fragmentation of filamets |
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If 100 bacteria cells grow for 5 hours they produce
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1720320 new cells. (EXPONENTIAL GROWTH)
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Exponential Growth
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Bacterial cells multiply at very fast rates.
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Microbial growth count
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number of living cells or total count (viabel count)
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Generation time
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time for complete cell division (G)
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4 phases of growth cureve
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Lag
Log Stationary Deth |
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Lag Phase
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Absorption of nutrients, active metabolites, synthesis of new protoplasm NO DIVISION
Length is variable in different species. |
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Log Phase (Exponential Phase)
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Cells devide at a constant and max rate.
Number and mass of cells doubling every generation, and new cells grow exponentially. It is BALANCED GROWTH. |
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Stationary phase
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Depletion of nutrients, build up of wastes (acids). Number of cells dying is the same as of those being created. CELLS ARE NOT UNIFORM, and are SMALLER than in log phase.
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Death Phase
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Cells gradually die off in decline phase.
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You can estimate bacterial numbers indirectly by:
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Metabolic activity
and Dry weight |
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Most Probable Number (MPN)
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Statistical estimating technique that is used to estimate #'s of bacteria in liquid medium.
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Fungus would be
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filtered, dried and weighed.
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Standard Plate Count
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Each bacterium grows in to a single colony which is reported as a number of colony forming units (C.F.U.)
Count by pour plate method or spread plate method. |
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Filtration
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Bacteria stay on the surface of the membrane filter and then transferred to medium to be grown and counted.
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Direct microscopic count
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the microbes in the measure volume of bacteria are counted with the use of a specially designed slide (cell counter)
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Spectophotometer
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Indirect method of measuring microbial growth. It is used to determine turbidity (cloudiness) by measuring the amout of lifth that passes through a suspension of a cell.
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Measurement of metabolic activity of the population
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Indirect method of measuring microbial growth. Oxygen consumption and acid production......
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Completely independent neighboring microbes
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Two different oragnisms that live side by side.
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Mutualism
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each organism benefits from another
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Commensalism
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One organism benefits but causes no harm.
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Microbiota
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Normal microbes that live on humans and cause no harm unless they have an opportunity (opportunists)
Eg. cut |
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Compete for space on humans and in colon.
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Bacteria and yeast
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Antibiotics may kill _____ bacteria and cause _______ one to grow
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good
pathogenic |
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Moisture
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Most bacteria favor moisture
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T.B and Staph can withstand _____ and can live in ______ or food for _____ periods.
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drying
dust long |
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Drying food is one method of
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food preservation
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Photosynthetic bacteria
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reacquire light
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Most bacteria like __________ envirnoments.
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warm, dark, alkaline and moist environments.
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