Test Two Text 4

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  1. Phases of growth can be performed with a bacterial growth curve
    • lag phase
    • log phase
    • stationary pahse
    • death phase
  2. Lag phase
    •                                                                i.      Lag phsase: number of cells changes very little; cells are not dormant; microbial population is undergoing a period of intense metabolic activity involving, in particular, synthesis of enzymes and various molecules
  3. Log Phase
    ii.      Log phase: cells begin to divide and grow rapidly; generation time is not constant; time when cells are most active metabolically
  4. Stationary phase
                                                                   i.      Stationary phase: growth rate slows and number of microbial deaths balances the number of new cells, and the population stabilizes
  5. Death phase
                                                                   i.      Death phase: number of deaths exceeds number of new cells formed and population enters death phase; phase continues until population is diminished to a tiny fraction of the number of cells in the previous phase or until the population dies out entiremly
  6. a.       Direct Measurement of Microbial Growth
                                                                   i.      Population numbers recorded as __
                                                                 ii.      More commonly done in a series of __
                                                                iii.      Plate counts: advantageous because it __; disadvantageous in that it __
    • number of cells in mL of liquid or gram of solid material
    • dilutions
    • measures number of viable cells
    • takes some time for visible colonies to form
  7. 1.       Plate counts assume that each live bacterium can grow __
    a.       Plate counts are often reported as __
    2.       When performing this, it is important that only a __
    • lined in chains or as clumps
    • colony-forming units (CFU)
    • limited number of colonies develop in the plate
  8.                                                                i.      __: diluting large concentrations of bacteria to make it more feasible to read
                                                                 ii.      Pour Plates and Spread Plates
    1.       __: 1.0 mL or 0.1 mL of dilutions of bacterial suspension is introduced into a __; the nutrient medium is poured over the sample and then mixed into mediumà solidifiesà incubatedà colonies grow within nutrient agar, as well as on surface
    a.       Bad because some heat-sensitive microbes may be damaged; it also alters the appearance of some bacteria
    • Serial dilutions
    • Pour plate method
    • Petri Dish
  9. 1.       __: 0.1 mL inoculum is added to the surface of a prepoured, solidified agar medium; inoculum is then spread uniformly over the surface of the medium with a specially shaped, sterilized glass, or metal rod
    Spread plate method
  10. i.      __: water passed through thin membrane to filter out bacteriaà filter transferred to Petri dish
    ii.      __: based on the fact that the greater the number of bacteria in a sample, the more dilution is needed to reduce the density to the point at which no bacteria are left to grow in the tubes in a dilution series; most useful when microbes __
    • Filtration
    • Most Probably Number (MPN) Method
    • will not grow on solid media
  11. i.      __: measured volume of a bacterial suspension is placed within a defined area on a microscopic slide; afterwards, a slide is made
    1.       __
    2.       Motile bacteria are hard to count by this method; and, dead cells are counted as live onesà both are disadvantageous
    • Direct Microscopic Count
    • Petroff-Hausser cell center
  12. a.       Estimating Bacterial Numbers by Indirect Methods
                                                                   i.      __: monitors bacterial growth; as bacteria multiply in liuid medium, the medium becomes __
    1.       A __is used, in which a beam of light is transmitted through a bacterial suspension to a light-sensitive detector
    a.       As bacterial numbers increase, less light will reach the detector à percentage of transmission
    • Turbidity
    • turbid, or cloudy with cells
    • spectrophotometer
  13.                                                                i.      __: assumes that the amount of a certain metabolic product is in direct proportion to the number of bacteria present
                                                                 ii.      __: for filamentous bacteria and molds
    1.       Method: fungus is removed from the growth medium, filtered to remove extrameous material, and dried in a dessicator; then, it’s weighed
    • Metabolic activity
    • Dry weight
  14. a.       The History of Chemotherapy
                                                                   i.      __ is credited with it; and __observed that penicillin was an effective antibiotic against bacteria
    1.       Mechanism of inhibition: __
                                                                 ii.      __: substance produced by microorganisms that in small amounts inhibits another rmicroorganism
                                                                iii.      More than half of our __are produced by species of __
                                                               iv.      Most antibiotics today were discovered by methods that required identifying and growing colonies of antibiotic-producing organisms
    1.       __ rapidly screen very large numbers of microbes in the serarch for new antibiotics
    • Pau Ehrlich
    • Fleming 
    • antibiosis
    • Antibiotic
    • antibiotics 
    • Streptomyces
    • High-throughput methods
  15. a.       Spectrum of Antimicrobial Activity
                                                                   i.      It is easy to find or develop drugs that are effective against prokaryotes and don’t affect eukaryotes; __ has numerous targets
    1.       So what is the problem?
                                                                 ii.      Some drugs have a narrow __,or range of different microbial types they affect
    • selective toxicity
    • The problem is more difficult when the pathogen is a eukaryote since they resemble human host cells
    • spectrum of microbial activity
  16.                                                                i.      Antibiotics that affect a broad range of gram-positive or gram-negative bacteria are called __
                                                                 ii.      A primary factor involved in the __ of antibacterial action lies in the __of gram-negative bacteria and the __ that form water-filled channels across this layer.
    1.       Drugs that pass through the porin channels must be __. Drugs that are __do not enter gram-negative bacteria readily
    • broad-spectrum antibiotics
    • selective toxicity
    • lipopolysaccharide outer layer 
    • porins
    • small or hydrophilic
    • lipophilic
  17.   i.      Advantage of broad-spectrum drug: __

                                                                 ii.      Disadvantage of broad-spectrum drug: __
    1.       Because normal microbes ordinarly compete with and check pathogen growth, an antibiotic that destroys the competitors allows __
    a.       __may occur, which may lead to a __, a term also applied to growth of a target pathogen that has developed resistance ot the antibiotic
    • saving valuable time
    • drugs destroy many normal microbes in the host
    • survivors to flourish and become opportunistic pathogens
    • Overgrowth 
    • superinfection
  18. a.       The Action of Antimicrobial Drugs
                                                                   i.      They are either __(they kill microbes directly) or __(they prevent microbes from growing)
                                                                 ii.      In bacteriostasis, what happens?
    • bactericidal 
    • bacteriostatic 
    • the host’s own defenses usually destroy the microorganism
  19.                                                                i.      Inhibiting cell wall synthesis        
    • 1.       Penicillin and certain other antibiotcs prevent the synthesis of intact peptidoglycan; the cell wall, as a result, is greatly weakened, and the cell  lyses
    • a.       Only actively growing cells are affected
  20.                                                                i.      Inhibiting protein synthesis 
           Due to structural differences in euk and pro ribosomes, eukaryotes have __ and prokaryotes have __ ribosomes

    a.       This difference accounts for __
                                                                                                                                           i.      Since mitochondria of eukaryotes also has __, they can sometimes be affected
    • 80S
    • 70S
    • selective toxicity of antibiotics that affect protein synthesis
    • 70S
  21.                                                                i.      Injuring the plasma membrane
    1.       Changes in __ take place, resulting in __
                                                                 ii.      Inhibiting nucleic acid synthesis
    1.       __
    • the permeability
    • loss of important metabolites form microbial cell
    • DNA replication and transcription is affected
  22.                                                                i.      Inhibiting Synthesis of essential metabolites
    1.       Sometimes, __ can affect synthesis in that it does what?
    a.       Ex: PABA is a substrate for an enzymatic reaction leading to the synthesis of __, a vitamin that functions as a coenzyme for the synthesis of the purine and pyrimidine bases of nucleic acids and many amino acids
    • competitive inhibition
    • competes with the substrate for the active site, reducing the amount of product that is formed
    • folic acid
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Test Two Text 4
2014-11-01 18:21:06
Test Two
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