INTRODUCTION
A light microscope (LM)
is an instrument that uses visible light and magnifying lenses to examine small
objects not visible to the naked eye, or in finer detail than the naked eye
allows.
The part of microscope.
http://mansfield.osu.edu/~sabedon/biol2010.htm#illustration_cocci
Eyepiece
Lens: the lens
at the top that you look through. They are usually 10X or 15X
power.
Tube: Connects the eyepiece to the objective lenses
Arm: Supports the tube and connects it to the base
Base: The bottom of the microscope, used for support
Illuminator: A steady light source (110 volts) used in place of a
mirror. If your microscope has a mirror, it is used to reflect light from
an external light source up through the bottom of the stage.
Stage: The flat platform where you place your slides.
Stage clips hold the slides in place. If your microscope has a mechanical
stage, you will be able to move the slide around by turning two knobs.
One moves it left and right, the other moves it up and down.
Revolving
Nosepiece or Turret: This is
the part that holds two or more objective lenses and can be rotated to easily
change power.
Objective Lenses: Usually you will find 3 or 4 objective lenses on a
microscope. They almost always consist of 4X, 10X, 40X and 100X
powers. When coupled with a 10X (most common) eyepiece lens, we get total
magnifications of 40X (4X times 10X), 100X , 400X and 1000X. To have good
resolution at 1000X, you will need a relatively sophisticated microscope with
an Abbe condenser. The shortest lens is the lowest power, the longest one
is the lens with the greatest power. Lenses are color coded and if built
to DIN standards are interchangeable between microscopes. The high power objective
lenses are retractable (i.e. 40XR). This means that if they hit a slide,
the end of the lens will push in (spring loaded) thereby protecting the lens
and the slide. All quality microscopes have achromatic, parcentered,
parfocal lenses.
Rack Stop: This is an adjustment that determines how close the
objective lens can get to the slide. It is set at the factory and keeps
students from cranking the high power objective lens down into the slide and
breaking things. You would only need to adjust this if you were using
very thin slides and you weren't able to focus on the specimen at high power.
(Tip: If you are using thin slides and can't focus, rather than adjust the rack
stop, place a clear glass slide under the original slide to raise it a bit
higher)
Condenser Lens: The purpose of the condenser lens is to focus the
light onto the specimen. Condenser lenses are most useful at the highest
powers (400X and above). Microscopes with in stage condenser lenses
render a sharper image than those with no lens (at 400X). If your
microscope has a maximum power of 400X, you will get the maximum benefit by
using a condenser lenses rated at 0.65 NA or greater. 0.65 NA condenser
lenses may be mounted in the stage and work quite well. A big advantage
to a stage mounted lens is that there is one less focusing item to deal
with. If you go to 1000X then you should have a focusable condenser lens
with an N.A. of 1.25 or greater. Most 1000X microscopes use 1.25 Abbe
condenser lens systems. The Abbe condenser lens can be moved up and
down. It is set very close to the slide at 1000X and moved further away
at the lower powers.
Diaphragm or
Iris: Many
microscopes have a rotating disk under the stage. This diaphragm has
different sized holes and is used to vary the intensity and size of the cone of
light that is projected upward into the slide. There is no set rule
regarding which setting to use for a particular power. Rather, the
setting is a function of the transparency of the specimen, the degree of
contrast you desire and the particular objective lens in use.
Magnification.
·
40x magnification
·
100x magnification
·
400x magnification
·
1000x magnification
OBJECTIVE
·
Learn to use a simple bright-field microscope
correctly.
·
To provide an experience in the use of
microscope.
·
To illustrate the diversity of cells and
microorganisms.
RESULTS
Species ; Streptococcus
sp
Magnification ; 40x
Species ; Streptococcus
sp.
Magnification ; 100x
Species ; Streptococcus
sp.
Magnification ; 400x
Species ; Lactobacillus fermentum
Magnification ; 1000x
DISCUSSION
1. Stained cell
Cocci (plural of coccus)
bacteria are found in circular smear. Cocci are too small to see below 10x,
100x and 400x. Although 1000x immersion oil magnification is done, individual
cocci are still barely visible.
There are few types of
arrangement of cocci shape ;
1.
Cocci [sing. Coccus]
- A bacterial shape.
- Generally
spherical though with some variation from this theme (i.e., elongation or
flattening on one side).
2.
Diplococci
- Cocci that remain in pairs after they divide.
3.
Streptococci
- Cocci that fail to separate after they divide, but instead
remain in chains of cells.
4.
Tetrad
- Cocci that fail to separate after they divide, but instead
remain in groups of four forming squares
5.
Sarcinae
- Cocci that fail to separate after they divide, but instead
remain in groups of eight forming cubes.
6.
Staphylococci
- Cocci that fail to separate after they divide, but instead
remain in amorphous sheets or clumps.
2. Wet mount
i. Saccharomyces is a genus in the kingdom of fungi that includes many species of yeast.
Saccharomyces cerevisiae is used in making wine,bread and beer. Colonies of Saccharomyces grow rapidly and mature in three days.
They are flat, smooth,
moist, glistening or dull, and cream to tannish cream in color. The inability
to use nitrate and ability to ferment various carbohydrates.
A coccus-shaped bacterium is usually spherical,
although some appear oval, elongated, or flattened on one side. Most cocci are
approximately 0.5 - 1.0 micrometer (µm) in diameter and may be
seen, based on their planes of division and tendency to remain attached after
replication. . Saccharomyces cerevisiae
are commonly reproduce asexually by budding. Unlike bacteria which are
prokaryote, Saccharomyces cerevisiae
are eukaryotic.
ii. Lactobacillus fermentum is a Gram-positive species of bacterium in the genus Lactobacillus. Species in this genus are used
for a wide variety of applications. These applications include food and feed
fermentation. It has been found that some strains for Lactobacillus fermentum have natural resistances to certain
antibiotics and chemotherapeutics.
They
are usually straight, although they can form spiral or coccobacillary forms
under certain conditions. They are often found in pairs or chains of varying
length.They
can grow at temp. 45°C. Lactobacillus
fermented belongs to arginine and ribose fermenting, a Betabacteria that
are important in spoilage microorganism of beer.
CONCLUSION
In conclusion, from this first lab, we learnt the
basic technique and procedure to use the light microscope correctly. We also
are now able to identify the specific function of each part of microscope.
Examined a stained cell (Streptococcus sp.),
Saccharomyces cerevisiae,
and Lactobacillus fermentum is the first trial
or experience in using light microscope. Different magnifications are used to
obtain clearer image of the stained cell and the wet mount. From the image
obtain through microscopy, we are able to illustrate the diversity of cells and
microorganisms. Besides, the description of morphology of the cells can be done
.
REFERENCES
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