basic lab

• Metric units


  Used to express the sizes of microbes
• Meter (m)


  The basic unit of length in the metric system, equivalent to 39.4 inches
• Metric System


  • Micrometers (μm)
  • Nanometers (nm)
• Micrometer (μm)


  One-millionth of a meter
• Typical spherical bacterium (coccus)

  • Approximately 1 μm in diameter
• Typical rod-shaped bacterium (bacillus)


  • Approximately 1 μm wide x 3 μm long
• Nanometer (nm)


  One billionth of a meter
• Viruses that cause human diseases

  • Range in size from 10 to 300 nm
• Ebola virus


  • Can be as long as 1,000 nm (1 μm)
• Ocular micrometer


  Used to measure the dimensions of objects being viewed with a compound light microscope
• Optical instruments


  • Process light waves to enhance an image for a clearer view
  • Have a limit as to what can be seen using that instrument, referred to as the resolving power or resolution
• Resolving power


  The ability of an optical system to differentiate between two closely spaced lines
• Unaided human eye


  Resolving power of approximately 0.2 mm
• Microscope


  An optical instrument used to observe tiny objects that cannot be seen with the unaided human eye