The purpose of a microscope is to magnify a small object or to magnify the fine details of a larger object in order to examine minute specimens that cannot be seen by the naked eye.
Here are the important microscope parts...
Eyepiece: The lens the viewer looks through to see the specimen. The eyepiece contains a 10X or 15X power lens.
Diopter Adjustment: Useful as a means to change focus on one eyepiece so as to correct for any difference in vision between your two eyes.
Body tube (Head): The body tube connects the eyepiece to the objective lenses.
Arm: The arm connects the body tube to the base of the microscope.
Coarse adjustment: Brings the specimen into general focus.
Fine adjustment: Fine tunes the focus and increases the detail of the specimen.
Nosepiece: A rotating turret that houses the objective lenses. The viewer spins the nosepiece to select different objective lenses.
Objective lenses: One of the most important parts of a compound microscope, as they are the lenses closest to the specimen.
A standard microscope has three, four, or five objective lenses that range in power from 4X to 100X. When focusing the microscope, be careful that the objective lens doesn’t touch the slide, as it could break the slide and destroy the specimen.
Specimen or slide: The specimen is the object being examined. Most specimens are mounted on slides, flat rectangles of thin glass.
The specimen is placed on the glass and a cover slip is placed over the specimen. This allows the slide to be easily inserted or removed from the microscope. It also allows the specimen to be labeled, transported, and stored without damage.
Stage: The flat platform where the slide is placed.
Stage clips: Metal clips that hold the slide in place.
Stage height adjustment (Stage Control): These knobs move the stage left and right or up and down.
Aperture: The hole in the middle of the stage that allows light from the illuminator to reach the specimen.
On/off switch: This switch on the base of the microscope turns the illuminator off and on.
Illumination: The light source for a microscope. Older microscopes used mirrors to reflect light from an external source up through the bottom of the stage; however, most microscopes now use a low-voltage bulb.
Iris diaphragm: Adjusts the amount of light that reaches the specimen.
Condenser: Gathers and focuses light from the illuminator onto the specimen being viewed.
Base: The base supports the microscope and it’s where illuminator is located.
How does a microscope work?
A light microscope works very much like a refracting telescope, but with some minor differences. Let's briefly review how a telescope works.
A telescope must gather large amounts of light from a dim, distant object; therefore, it needs a large objective lens to gather as much light as possible and bring it to a bright focus. Because the objective lens is large, it brings the image of the object to a focus at some distance away, which is why telescopes are much longer than microscopes. The eyepiece of the telescope then magnifies that image as it brings it to your eye.
In contrast to a telescope, a microscope must gather light from a tiny area of a thin, well-illuminated specimen that is close-by. So the microscope does not need a large objective lens. Instead, the objective lens of a microscope is small and spherical, which means that it has a much shorter focal length on either side. It brings the image of the object into focus at a short distance within the microscope's tube. The image is then magnified by a second lens, called an ocular lens or eyepiece, as it is brought to your eye.
The other major difference between a telescope and a microscope is that a microscope has a light sourceand a condenser. The condenser is a lens system that focuses the light from the source onto a tiny, bright spot of the specimen, which is the same area that the objective lens examines.
Also unlike a telescope, which has a fixed objective lens and interchangeable eyepieces, microscopes typically have interchangeable objective lenses and fixed eyepieces. By changing the objective lenses (going from relatively flat, low-magnification objectives to rounder, high-magnification objectives), a microscope can bring increasingly smaller areas into view -- light gathering is not the primary task of a microscope's objective lens, as it is a telescope's.
OBJECTIVE
- Learn how to use microscope correctly
- To expose the student tne about the shape and activity of microorganism
RESULTS
- Stained cells
penicillium spp.
DISCUSSION
Penicillium spp. are widespread and are found in soil,
decaying vegetation, and the air. Showing again how it is distinct from other
species in this genus, Penicillium spp. is endemic specifically in Southeast
Asia where it infects bamboo rats which serve as epidemiological markers and
reservoirs for human infections. For Penicillium species, septate hyaline
hyphae (1.5 to 5 µm in diameter), simple or branched conidiophores, metulae,
phialides, and conidia are observed. Metulae are secondary branches that form
on conidiophores. The metulae carry the flask-shaped phialides. The
organization of the phialides at the tips of the conidiophores is very typical.
They form brush-like clusters which are also referred to as
"penicilli". The conidia are round, unicellular, and visualized as
unbranching chains at the tips of the phialides. At 37°C, Penicillium spp. colonies
are cream to slightly pink in color and glabrous to convoluted in texture.
The second method which is wet mounts remains the most
widely used method for identifying ova and cysts of parasites from stool
specimens (Valentina & Lalitha, 2001). The classical technique described
for the microscopic examination of parasites is the iodine mount method, which
facilitates the differentiation and identification of parasites by characteristic
morphological features and details of internal structures. The method is easy,
less time-consuming and inexpensive, allowing direct visualization of parasitic
ova and cyst morphology. The only disadvantage to this technique is that the
preparation dries within a few minutes, rendering it unreadable.
Saccharomyces cerevisiae is a species of yeast. It is
perhaps the most useful yeast, having been instrumental to baking and brewing
since ancient times. It is believed that it was originally isolated from the
skin of grapes (one can see the yeast as a component of the thin white film on
the skins of some dark-colored fruits such as plums; it exists among the waxes
of the cuticle). It is one of the most intensively studied eukaryotic model
organisms in molecular and cell biology, much like Escherichia coli as the
model bacterium. It is the microorganism behind the most common type of
fermentation. S. cerevisiae cells are round to ovoid, 5–10 micrometres in
diameter. It reproduces by a division process known as budding.
Lactobacillus fermentum is a Gram-positive species of
bacterium in the genus Lactobacillus. It is associated with active dental
caries lesions. It is also commonly found in fermenting animal and plant
material. It has been found in sourdough. A few strains are considered
probiotic or "friendly" bacteria in animals and at least one strain
has been applied to treat urogenital infections in women. Some strains of
lactobacilli formerly classified as Lactobacillus fermentum (such as RC-14)
have since been reclassified as Lactobacillus reuteri. Commercialized strains of
L. fermentum used as probiotics include PCC and ME-3. It is rod-shaped and
straight. But under the certain conditions, they also can form spiral or
coccobacillary. They are often found in pairs or chains of varying length.
CONCLUSION
There
are gram-positive and gram-negative bacteria. For gram-negative bacteria, they have thin cell wall and no peptidoglycan which is stain with pink colour.Example of this gram-negative bacteria is Penicillum spp. For gram-positive bacteria, they have thick cell wall of peptidoglycan which is
stain with purple colour. Example of gram-positive bacteria is Lactobacilli fermentum.
Different type of bacteria had examine during the lab session. There are variety of shape,colour and size of bacteria had been examine using microscope. There are correct way to using a microscope to obtain the good results.
REFERENCE
- http://www.doctorfungus.org/thefungi/penicillium.php
- http://en.wikipedia.org/wiki/Saccharomyces_cerevisiae
- http://en.wikipedia.org/wiki/Lactobacillus_fermentum
- http://jmm.sgmjournals.org/content/57/5/679.full
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