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95 Cards in this Set

  • Front
  • Back
Physical requirements for microbial growth?
Temperature: Minimum, Optimum and Maximum.
Osmotic pressure:
Acidophiles grow in ________ environment.
Most bacteria grow between pH of ___ and ___.
6.5 to 7.5
Molds and yeast grow between pH of ___ and ___
5 - 6
shrinking of the cell's cytoplasm
What causes plasmolysis?
Hypertonic environments, the increase in salt or sugar.
Extreme or obligate halophiles require?
High osmotic pressure and salt. Eg. Dead Sea. (30% salt environment)
Faculative halophiles tolerate?
High osmotic pressure. (2% salt environment)
Chemicals required in microbial growth
Trace elements (inorganic required in small amounts)
Nitrogen is found in?
Amino acids, proteins
Most bacteria decompose
Some bacteria use
NH4+ andNO3-
Sulfur is found
in amino acids, thiamine, biotin
Phosphorus is found in
DNA, RNA, ATP and membranes
PO4 3- is a source of _____.
Trace elements
inorganic elements required in small amounts. They are usually enzyme co factors: Iron, copper, zinc.
Naturally present in tap water.
Carbon is a
structural organic molecule, energy source
Chemoheterotrophs use organic carbon sources
Autotrophs use CO2.
cause infection in warm blooded animals eg. humans
Endospores may survive usual ________
heat treatments. Eg. canning
Most bactaria can withstand slight changes in ________ pressure
Hypertonic environments
increase salt or sugar, and cause plasmolysis. (water out of the cell)
Extreme or obligate halophiles regire
HIGH osmotic pressure
Isotonic solution is ____________%NaCl
0.85-0.9 %NaCl
Hypertonic sloution is ______%Nacl
Obligate anaerobes
No oxygen, LACK ENZYMES. Grow in deep wounds with O2.
Facultative anaerobes are
both aerobic and anaerobic but BETTER IN O2 for growth.
They HAVE the enzymes.
Aerotolerant anaerobes
only grow anaerobically but continue in presence of O2
Micro aerophilic
O2 is reqired in low concentration
Aerobes need O2 as a final
(e-) exceptor in electron transport pathway but toxic chemical and free radicals are produced. However, aerobes have enzymes to handle them.
Catalase enzyme
ID bacteria as catalase + or -
Peroxidese enzyme and superoxide dismotase (SOD)
break down superoxide free radicals (O2-)
Organic growth factors
vitamins, amino acids, purines and pyrimidines
Culture medium
nutrients are prepared for microbial growht. Has to be sterile before exposure.
introduction of microbes in to medium
Microbes growing in/on culture medium
Complex polysaccharide
derivative from alge and used used as solidifying agent for culture medai in Petri dishes, slants and deeps in lab.
Generally not metabolized by microbes
complex polysaccharides
Liqefies at 100 degrees celsius
Agar solidifies at _______ degrees celsius
Chemically defined media
exact chemical composition is known
Complex Media
Exactract and digest of yeasts, meat or plants.
Nutrient broth (soup)
Nutrient agar
Fastidious microbes
Require many growth factors Eg. Lactobacilus
Short chains of amino acids are digested by _______ ________
most bacteria
Reducing media
Contains chemicals tioglycollate or oxyrase, that combine with O2 and drive it off
Selective media
supresses unwanted microbes and encourages disered microbes. Eg. Streptococus and not any other bacteria.
Eosin Methylene Blue (EMB)
isolated gram -ve coliforms
Coli-type colonies are very ____ color.
dark eg. lactose +
Aerogenes-type colonies are less _______ color.
dark eg. lactose -
Differential media
Makes it easier to distinguish colonies of desired organism
Eg. Tellurite-Glycine Agar: completly inhibits growth of coaguase-negative staphylococci
is an enzyme produced by staphloccoccus aureus that converts fibrogen to fibrin.
Potassium tellurate
Differential agent in the differential medium.
Coagulase-positive staphylococcus reduce tellurite produces black colonies.
Media can be both ________ and _________.
Differential and Selective

Eg. Mannitol ssalt agar. High salt selects for S. aureus and mannitol fermentation differentiates them from non-mannitol fermenting bacteria.
Enrichment Media
Encourages growth of desired microbe.
A pure culture
contains only ONE SPECIES or STRAIN
A colony
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.
Colony is often called "colony forming unit"
Defferental meadia make it easier to
distinguish colonies of desired organisms from other colonies.
Eg. red blood cells (sheep), certain kind of bacteria produce hemolysis on the plate.
Manitol Salt Agar
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)
MacConkeg's Agar
Both selective and differential. Bilesalts and crystal violet inhibits growth of G+ bacteria. It encourages lactose fermentors
Selective Media
suppresses growth of unwanted bacteria but encourages growth of desired ones.
Sabourd's Media
Dextraose with pH5.6 to isolate fungi that outgrow most bacteria.
Dies such as brilliant green inhibit
gram (+)ve bacteria.
Preserving bacterial culture is done by:
Deep freezing: -50 - -90 degreees celsius and
Lyophilization: freeze-drying
freeze-drying. Bacteria are frozen at (-54)-(-95) degrees celsius and dehydrated in a vacuum (sublimation)
Dehydrating of bacteria in a vacum
Preserved residue containing surviving microbes can be revived by __________ yealrs later.
Prokaryote ways of reproduction
Binary fussion
Conidiospores (actinomycetes)
Fragmentation of filamets
If 100 bacteria cells grow for 5 hours they produce
1720320 new cells. (EXPONENTIAL GROWTH)
Exponential Growth
Bacterial cells multiply at very fast rates.
Microbial growth count
number of living cells or total count (viabel count)
Generation time
time for complete cell division (G)
4 phases of growth cureve
Lag Phase
Absorption of nutrients, active metabolites, synthesis of new protoplasm NO DIVISION
Length is variable in different species.
Log Phase (Exponential Phase)
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.
Stationary phase
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.
Death Phase
Cells gradually die off in decline phase.
You can estimate bacterial numbers indirectly by:
Metabolic activity
Dry weight
Most Probable Number (MPN)
Statistical estimating technique that is used to estimate #'s of bacteria in liquid medium.
Fungus would be
filtered, dried and weighed.
Standard Plate Count
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.
Bacteria stay on the surface of the membrane filter and then transferred to medium to be grown and counted.
Direct microscopic count
the microbes in the measure volume of bacteria are counted with the use of a specially designed slide (cell counter)
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.
Measurement of metabolic activity of the population
Indirect method of measuring microbial growth. Oxygen consumption and acid production......
Completely independent neighboring microbes
Two different oragnisms that live side by side.
each organism benefits from another
One organism benefits but causes no harm.
Normal microbes that live on humans and cause no harm unless they have an opportunity (opportunists)
Eg. cut
Compete for space on humans and in colon.
Bacteria and yeast
Antibiotics may kill _____ bacteria and cause _______ one to grow
Most bacteria favor moisture
T.B and Staph can withstand _____ and can live in ______ or food for _____ periods.
Drying food is one method of
food preservation
Photosynthetic bacteria
reacquire light
Most bacteria like __________ envirnoments.
warm, dark, alkaline and moist environments.