Lab 2 microbiology

Light vs electron microscope

• Light microscope uses visible light for illumination

• Electron microscope uses electron beams for illumination

Types of light microscopes

• Brightfield/ compound microscope = specimen will be dark

• Darkfield micrscope = speciment will be bright

• Phase contrast microscope = specimen seen in black and white

• Flourescent microscope = specimen is seen in various colors

Magnification definition

Enlargement of a specimen

Total magnification (equation)

objective lens x ocular lens = objective lens x 10

Resolving power or resolution definition

how far apart two adjacent objects must be before a given lens shows them as discrete

Resolving power (equation)

resolving power = wavelength of light/ 2 x numerical aperture

Three shapes of bacteria

• Spherical (cocci)

• Rod - shaped (bacilli)

• Spiral - shaped

Spherical (cocci) examples

• Streptococcus pneumoniae

• Streptococcus pyogenes

Rod shaped (bacilli) examples

• bacillus anthracis

• salmonella enterica

spiral shaped examples

• vibrio cholerae

• helicobacter pylori

Types of staining techniques

simple staining
differential staining

Peptidoglycan

a protein that makes up bacterial cell wall

What is gram positive and the color?

color = purple

A thicker peptidoglycan

What is gram negative and the color?

color = pink

a thinner peptidoglycan

Types of stains

• primary stain - application of crytal violet

• mordant - application of grams iodine

• decolorizing agent - 95% alcohol wash

• counterstain - application of safranin