Lecture 4 Flashcards
Why use the pour plate method
Allows us to see which bacteria needs oxygen and which doesn’t need oxygen
-some bacteria could grow on surface but others could grow underneath (which we would not be able to see if we plated normally)
What do smooth cells in a biofilm mean
They were cheaters
What are cheaters in biofilm
Free riders without contributing to common goods
Who was the first to observe microorgansims
Anton van Leeuwenhoek
-was able to see up to 300x w/ microscope
What is the highest objective lens?
100x
-100 x 10 = 1000x total
How is total magnification calculated?
(objective lens x ocular lens = total )
-ocular lens = 10x
Is being negatively charged cell different from being gram negative?
Yes negative refers to charge, gram negative refers to cell wall
Why do we use crystal violet to stain cells
-Cells are (-) charged, crystal violet is (+) charged so it stains
Gram (+)
Retains stain–>purple
Gram (-)
Does not retain the 1st dye–> pink
True or false: at a higher magnification the light refracts
True
Why does refraction occur?
Refraction index changes
-light bends when it enters a substance that changes its speed
How do we improve resolution/stop refraction?
Use mineral immersion oil
How does immersion oil prevent light rays from bending away from objective lens?
Immersion oil covers distance between glass and obj lens (like a bridge)
- light does not bend since the oil has the same refraction index as light
What are rod shaped bacteria called
Bacilli/Bacillus
