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level: Level 1

Questions and Answers List

level questions: Level 1

QuestionAnswer
DiaphragmWhich part of the light microscope controls the intensity of light entering the viewing area?
Crystal violet, iodine solution, alcohol, safraninWhat is the correct order of gram-staining
Gram PositiveWhich bacteria appears purple-violet colour after staining?
MordantIn Gram-staining, iodine is used as a?
Used as a fixative prior to staining in light microscopyHeat
To reduce the number of bacteria on a dish to a know factor, in order to count population sizeSerial Dilution
No. of Bacteria= colony number/(dilution rate x ml of sample)Calculations for counting no. of bacteria.
Provides well segregates colonies. All bacteria grow from a single parent cell (isolated, no contamination). Creates a pure culture.Streak plating
Done after incubation. Only chose plates with 30-300 CFU’sCounting
Colony forming Unit. Used to estimate the number of viable bacteria or yeast. Shown as CFU per g/ml/cm2 etc.CFU
Measurement of the number od bacterial cells per ml, g, cm3 etc..Bacterial Enumeration
Involve counting cells that can be cultured and/or metabolically activeViable Counts
Counting all cells: dead, inactive and aliveTotal Counts
Counting actual cells of coloniesDirect method of enumeration
Estimate numbers based on call mass, spectroscopy or statistical methodsIndirect method of enumeration
Used for direct and viable countingStandard plate count
Used for direct and total countingFluorescent staining and microscopy
Used for indirect and viable countingMPN
Used for indirect and tota countingSpectroscopy
Measuring amount of light that passes through a liquid culture using a spectrophotometer and estimated number of cells from the light that passes throughSpectroscopy
Make statistical estimates by patten growth in liquid culture mediaMPN
Used in serial dilution (saline)Ringers solution
Between 30 and 300Number of colonies when enumeration
Inhibits the growth of some bacteria while selecting for the growth of othersSelective media
Selective media. Dyes inhibit Gram +ve bacteria and selects Gram -ve. Most GI tract infections caused by Gram -ve.Brilliant Green Agar
Eosin Methylene Blue. Selective media. Dyes inhibit Gram +ve bacteria and selects Gram -ve. Most GI tract infections caused by Gram -ve.EMB
Differentiates between different organisms growing on the same plateDifferential Media
Differential Media. Use to differentiate between different types of streptococci (E.g. Alpha, Beta and Gamma haemolytic streptococci)Blood Agar Plates
Alpha= incomplete lysis of RB.> Beta= complete lysis. Differential media used.Alpha, Beta and Gamma Haemolytic streptococci
Selective AND Differential Media. Used to identify Staphylococcus aureus. High salt conc. pH indicator.Mannitol Salt Agar
Selective AND Differential Media. Identifies salmonella. Contains bile salts, crystal violet, lactose, pH indicator.MacConkey’s Agar
A x 10b= log (A x 10b) =(log A) x (log10b)*=log A+ bLog Value Calculation
Selective media for staphylococcusBaird Parker Agar
Selective media for yeastMalt Extract Agar
Selective mediaBrilliance salmonella agar
Selective media for bac. CereusBrilliance Bacillus cereus agar
Selective media for pseudomonasPseudomonas’s selective agar
Crustal violetPrimary stain (in gram staining)
Heat them iodineFixative (in gram staining)
AcetoneDecolouriser (in gram staining)
SafarinCounterstain (in gram staining)
For viewing the object. X 10 magnificationOcular lens (microscope)
Adjusts and holds the eyepiece (custom for each user)Body Tube (microscope)
Holds the objective lens- rotates to allow different lens to be chosenNose piece (microscope)
4 different lenses. X10, x100, x40, oil immersion lens (for mineral oils)Objective lens (microscope)
Objective lens x ocular lensTotal magnification (microscope)
Holds the slide and therefore sample in placeObject holder/mechanical stage clips (microscope)
used to vary the intensity and size of the cone of light that is projected upward into the slideIris or Diaphragm (microscope)
The purpose of the condenser lens is to focus the light onto the specimenCondenser lens (microscopy)
Moves object horizontally. Front to back, left to rightStage controls
Works with fine focus. Moves object up and down rapidly to get object into viewRough/coarse focus
Moves object up and down finely/smoothly. Gets sample into focus after coarse focus used.Fine/focus
is the use of certain growth media to favour the growth of a microorganism over others. E.g.. Media with a high salt concentration will select for halophilesEnrichment media
=log (A x 10^b) =(logA) x (log 10^b) =log (A+B) because log10=1A x 10^b