OCTC micro chapter 4

Microscopy refers to?
The use of light or electrons to magnify objects.

The distance between crest to crest in the waves.



Magnification occurs?
When a beam of light refracts or bends as it passes through a convex lens.
Magnification can increase?
virtually w/out limit by resolution (ability to see detail) cannot increase without limit.
Resolution is the ability?
to distinguish between two objects that are very close together.
Resolution determines?
How much detail is seen.
Electron microscope
Uses electron beams that have a much smaller wavelength than visible light.
The Scanning Electron Microscope
Can resolve microbes and magnify them 100,000 times more than a light or Brightfield microscope that we use in our labs.
Simple microscope

one lens =

magnifying glass

Compound microscope

have at least two lens

(objective lens and ocular lens)

Our Compound Microscopes have?

Objective lens

Ocular lens &

a Condenser lens

Objective lens

4x=scanning objective (red)


10x=low power objective (yellow)


40x=high power objective or high and dry objective

(blue band)


100x=oil immersion objective (white band)

lamp located in base of microscope that gives off visible light to illuminate specimen.

special lens beneath the mechanical stage that focuses rays of light to a single point on a specimen. 


(Condenser can be adjusted vertically)

Mechanical stage 
allows the operator to move a slide around smoothly during viewing by use of stage control knobs.
Why do microbioligists stain there specimens?

to create contrast.


Staining cells increases contrast, but requires that the cells are killed. 


(Killing microbes can distort specimen)

Dyes are used to?

Stain microbial cells and increase contrast.


(Methylene blue, crystal violet, and saffranin are examples of dyes)

Bright field microscopes

 (Used to observe arrangement, shape and size of killed, stained specimens.)

Microbes are dark against clear, bright background.

 Most common type of microscope

(viruses not seen)


Dark-Field Microscopes

(Living cells and movement)

Pale, small, colorless microbes are best observed.

 (light hits the sides of the specimen against a dark background.)


King-    Kingdom

Phillip-  Phyllum

Came-  Class

Over-   Order

For-     Family

Good-  Genus

Sex-    Species


3 Domain system






(colony forming unit)

Light microscopes

Light waves that are in phase are aligned, crest to crest and trough to trough.


Crests and troughs reinforce one another to produce a brighter image.

Phase-contrast microscopes

Brighter = (in-phase)

Used to examine living microbes or specimens.


(cell movement with cilia,flagella or phagocytosis)

Differential Interference Contrast Microscopes


Darker = (Out of phase)


Nomarski microscopes


gives a detailed view of unstained, live specimens by manipulating light which makes the specimen appears as 3D.

Photosynthetic archaea



What organism is responsible for generating the early earths atmosphere?




most common group of bacteria associated with humans and animals.

Fluorescent microscopes

(Ultra Violet radiation)

UV light increases resolution because it has a shorter wavelength than visible light.

Used as accurate and a quick diagnostic tool for detecting pathogens. 


Bacteria form
Protozoa form?

Transmission Electron Microscope


Thin, transverse sections (slice) (floor plan)

Examine fine details of internal cell structure.

Number layers of the cells envelope.


Categories: Microbiology