Microbiology Lab - Exam 1

• objectives

  usually 3 magnifications: 10X, 40X, and 100X. powers of the objective are also distinguished by colored rings
• occular lenses


  located at the top of the microscope and lie closest to your eyes, have a 10x magnification
• total magnification


  objective x 10
• magnification


  the size of the object under the microscope, number is portrayed as the total magnification when looking at any image
• resolution


  distance between two objects
• contrast


  light difference between two objects
• occulars

  a system of lenses that usually magnify the primary image ten times
• thumbwheel


  an adjustment to accommodate the distance between the observer's eyes
• revolving nosepiece


  a platform that can be rotated to switch from one objective to another
• slide holder


  spring-loaded holder that keeps the microscope firmly in place on the stage
• diaphragm lever


  opens and closes the condenser diaphragm to control the amount of light striking the specimen
• condenser


  condenses light rays into a cone, thereby controlling the intensity of illumination, increase/decrease in light
• condenser adjustment


  raises and lowers the condenser assembly
• mechanical stage and stage controls

  allows the slide to be moved in a horizontal plane
• light intensity control

  turns the light source on and off and controls the intensity
• adjustment knobs


  moves the stage up and down to focus on a specimen
• oil objective


  100x
• streak plating

  isolation of colonies and sterilization technique
• pure culture


  when aseptic technique is properly executed you are left with what?
• Smear prep

  heat fixing bacterium to the slide so it doesn't wash off, prep for gram stain.
• negatives of heat fixing

  kill bacteria

  - not moving

  - changes shape
• form

  punctiform, circular, filamentous, irregular, rhizoid, and spindle
• punctiform


  tiny, pinpoint

  
• filamentous


  thread-like

  
• irregular


  not circular, may be spreading

  
• rhizoid


  root-like

  
• spindle


  long and thin like a spindle

  
• Elevation


  flat, raised, convex, pulvinate, and umbonate
• flat


  lies completely flat along the surface of the medium

  
• raised


  has its top above the medium but still parallel with the surface

  
• convex


  mound

  
• pulvinate


  similar to convex, but is higher off the plate

  
• umbonate

  has a higher center than the edges

  
• margin

  entire, undulate lobate, serrated, filamentous, and curled
• entire


  circular

  
• undulate


  wavy

  
• filamentous


  fibrous or cotton like in appearance

  
• gram stain


  staining method that allows for us to test if a bacterium is gram negative or gram positive - based on the peptidoglycan layer
• steps of gram staining

  1. crystal violet

  2. iodine

  3. decolorizer

  4. safrinin
• gram negative

  pink