国外微生物学基础实验(一 )-英文版

Lab Report #1 and Pre-lab #2 and #3 due in lab next week, BEFORE LAB BEGINS!
Laboratory 1
Microscopy & Simple Stains
Your Light Microscope
CORDS are in the drawer.
Objective Lenses
High Dry Objective Lens
Has blue band around it.
Magnifies objects 40x.
Total magnification = 400xTM
Move up to this lens after focusing your smear at 100xTM.
End of Today’s Lab IMPORTANT!!!! Before next week, print out two copies of all labs (exercise & report), so that you have a “clean” copy and a “dirty” copy and keep these in a binder that you bring with you to class/lab. Each week I will tell you which exercises you will need to have out in lab. •
BASE
Microscopy
General Principles Magnification:
• • • What is it? Apparent increase in size of an object. Indicated by a number and “X”, which is read “times”.
Contrast:
• • • What is it? Difference between the object and the background Easiest ways to improve contrast are to use dye and/or manipulate light
Microscopy – Light Microscopes
2-D image: Transmission Electron Micrograph
A transmission electron micrograph of Escherichia coli (E.coli).
Scanning Electron Microscope (SEM):
3-D i源自文库age: Scanning Electron Micrograph
SEM AIDs virus attacking T4 lymphocyte
Procedure
Learning to use the compound light microscope
1. How to make a wet mount 2. Letter “e” Wet mount What happens to the “e” when you look at it through the lens? 3a. Onion Wet mount, use stain Note nucleus and cell wall or 3b. Elodea Wet mount NO stain Depth of field 2 layers of cells Note cell wall, chloroplasts streaming
Welcome to Lab!
Getting Ready for Today’s Lab • Stash backpacks in cubbies on right side of room. • • Choose your seat. Put on your “lab coat” and set goggles, a „dirty‟ copy of lab exercise/report #1 and your lab card on bench next to you. (The other copy of the lab exercise and report should be in your backpack. This is your „clean‟
You will not see individual bacteria with this lens, you are just using it to focus so that you can move up to the next magnification.
Remember the term parfocal?
Do not move the focus knob or the stage when placing the finger cot on the high dry lens or you will take the image out of focus!
NEVER use coarse focus with high dry or oil immersion lenses!!!
GETTING YOUR SCOPE OUT:
When transporting your scope, always hold it with one hand under the base, and one hand around the arm.
PUTTING SCOPE AWAY: Whenever your are getting ready to put your scope away:
Objective Lenses
Low Power Objective Lens
Has yellow band around it. Magnifies objects 10x. Total magnification = 100xTM
Start with this lens to get your bacterial smear into crisp focus.
copy.)
•
TURN IN: Pre-Lab #1 BEFORE LAB BEGINS!
•
Come get the following handouts:
- “Lab Cards” that you will be using each lab for sign in and sign out. - Signature page.
OBSERVATION OF MICROORGANISMS
Objective Lenses Scanning Objective Lens
Has red band around it.
Magnifies objects 4x.
Total magnification = 40xTM
This lens is of no use to us in looking at bacterial stains.
Onion Cells
Elodea
Cheek Cells
4. Cheek cell Wet mount using NaCl Try to view, then add stain. Contrast!
Before you get started, I want you to prepare a slide with a bacterial sample.
TAKE CARE OF YOUR SCOPE:
Your responsibility to take care of your scope and learn to use it properly.
ARM
MICROSCOPE LOG:
Every time that you get your scope out, you will make an entry in the microscope log.
• Use alcohol swab to clean stage and lens paper to clean lenses. • Shortest lens (the one with the red band) should be facing down toward stage. • Use course focus to position stage as low as it can go.
Resolution:
• • •
•
What is it? The ability to distinguish between objects that are close together. The optometrist‟s eye chart is a test of resolution at a distance of 20 feet. Limits maximum magnification
Bright-field Compound Microscope
AT THIS POINT, GO GET A SCOPE AND SIGN IT OUT.
Microscopy – Light Microscopes
Bright-Field Microscope
Light microscope produces a dark image against brighter background. Commonly used to view stained cells. Simple microscopes have single magnifying lens (like a magnifying glass). Compound microscopes have two sets of lenses for magnification. Lens closer to the eye = ocular lens (magnifying
Oil Immersion Objective Lens
Has black and a white band around it. Magnifies objects 100x. Total magnification = 1000xTM Move up to this lens after focusing your smear at 400xTM and covering the 400xTM lens with a finger cot.
NEVER use coarse focus with high dry or oil immersion lenses!!!
Microscopy – Electron Microscopes
Two types: Both huge, expensive machines. Transmission Electron Microscope (TEM):
You will not be able to clearly see individual bacteria with this lens. Just get the image in focus as much as possible.
High Dry Objective Lens
After you focus the image at 400xTM, you need to cover this lens with a finger cot so that it does not get oil on it.
power of 10x).
Objective Lenses Ocular lenses
Lenses closer to the object being viewed = objective lens. (Most light microscopes used in
biology have three or four objective lenses).