INTRODUCTION
Light microscopes, which we are using, use light to produce their images.
Scanning light microscopes are called dissecting microscopes, and there are many kinds
of light-transmission scopes, named for the way the light is delivered. Our lab
has mostly bright field compound
microscopes - specimens are seen against a bright
background, and several (compound) magnifications can be chosen by rotating the objective lenses. The
magnification of the objectives - commonly 4X, 10X, 40X, and 100X - are
magnified again by the eyepiece or ocular lenses - usually 10X - so the total magnification for the different objectives are 40X
(4x10), 100X (10x10), 400X (40x10), and 1000X (100x10).
Microscope Handling
- Carry the microscope with both hands, one on the arm and the other under the base of the microscope.
- Go over to the microscope storage area and properly transport one microscope to your working area.
- Then, pick up a pair of scissors, newsprint, a slide, and a cover slip.
- Remove the dust cover and store it properly. Plug in the scope. Do not turn it on until told to do so.
- Examine the microscope and give the function of each of the parts listed on the right side of the diagram.
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Student should be able
to:
1.
properly care for and
confidently use microscope
2.
Identify the structure
of microscope
3.
Use proper technique
with oil immersion lens and wet mounts
RESULT
1)
Stained cell
FIGURE 1
Penicillium spp
40x magnification
FIGURE 2
Penicillium spp
100x magnification
FIGURE 3
Penicillium spp
400x magnification
2)
Wet mount
FIGURE 4
Saccharomyces cerevisiae
1000x
magnification
FIGURE 5
Lactobacillus fermentum
1000x magnification
DISCUSSION
Gram staining (or Gram's method) is a method of
differentiating bacterial species into two large groups (Gram-positive and
Gram-negative).It is based on the chemical and physical properties of their
cell walls. Primarily, it detects peptidoglycan, which is present in a thick
layer in Gram positive bacteria.A Gram positive results in a purple/blue color
while a Gram negative results in a pink/red color.The Gram stain is almost
always the first step in the identification of a bacterial organism, and is the
default stain performed by laboratories over a sample when no specific culture
is referred.
Penicillium is a genus of ascomycetous fungi of
major importance in the natural environment as well as food and drug
production. Members of the genus produce penicillin, a molecule that is used as
an antibiotic, which kills or stops the growth of certain kinds of bacteria
inside the body. The thallus (mycelium) typically consists of a highly branched
network of multinucleate, septate, usually colorless hyphae. Many-branched
conidiophores sprout on the mycelia, bearing individually constricted
conidiospores. The conidiospores are the main dispersal route of the fungi, and
often are green in color.Sexual reproduction involves the production of
ascospores, commencing with the fusion of an archegonium and an antheridium,
with sharing of nuclei. The irregularly distributed asci contain eight
unicellular ascospores each.Penicillium is a gram-negative.
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.Many proteins
important in human biology were first discovered by studying their homologs in
yeast; these proteins include cell cycle proteins, signaling proteins, and
protein-processing enzymes. The petite mutation in S. cerevisiae is of
particular interest.Saccharomyces cerevisiae is currently the only yeast cell
that is known to have Berkeley bodies present, which are involved in particular
secretory pathways.Antibodies against S. cerevisiae are found in 60–70% of
patients with Crohn's disease and 10–15% of patients with ulcerative colitis.
Lactobacillus, also called Döderlein's bacillus, is
a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped
bacteria. They are a major part of the lactic acid bacteria group, named as
such because most of its members convert lactose and other sugars to lactic
acid. In humans they are present in the vagina and the gastrointestinal tract,
where they are symbiotic and make up a small portion of the gut flora. They are
usually benign, except in the mouth where they have been associated with
cavities and tooth decay (dental caries). Many species are prominent in
decaying plant material. The production of lactic acid makes its environment
acidic, which inhibits the growth of some harmful bacteria. Several members of
the genus have had their genome sequenced. Some Lactobacillus species are used
for the production of yogurt, cheese, sauerkraut, pickles, beer, wine, cider,
kimchi, cocoa, and other fermented foods, as well as animal feeds, such as
silage. Sourdough bread is made using a "starter culture," which is a
symbiotic culture of yeast and lactic acid bacteria growing in a water and flour
medium. Lactobacilli, especially L. casei and L. brevis, are some of the most
common beer spoilage organisms. The species operate by lowering the pH of the
fermenting substance by creating the lactic acid, neutralising it to the
desired extent.
Now we know how to handle microscope properly and
other precaution that we need to take care
about. It to avoid us from taken damage from microscope and spoil it
because microscope have a sensitive part.
Use an oil immersion lens when you have a fixed
(dead - not moving) specimen that is no thicker than a few micrometers. Even
then, use it only when the structures you wish to view are quite small - one or
two micrometers in dimension. Oil immersion is essential for viewing individual
bacteria or details of the striations of skeletal muscle. It is nearly
impossible to view living, motile protists at a magnification of 1000x, except
for the very smallest and slowest. A disadvantage of oil immersion viewing is
that the oil must stay in contact, and oil is viscous. A wet mount must be very
secure to use oil. Oil immersion lenses are used only with oil, and oil can't
be used with dry lenses, such as your 400x lens. Lenses of high magnification
must be brought very close to the specimen to focus and the focal plane is very
shallow, so focusing can be difficult. Oil distorts images seen with dry
lenses, so once you place oil on a slide it must be cleaned off thoroughly
before using the high dry lens again. Oil on non-oil lenses will distort
viewing and possibly damage the coatings.
To use an oil immersion lens, first focus on the
area of specimen to be observed with the high dry (400x) lens. Place a drop of
immersion oil on the cover slip over that area, and very carefully swing the
oil immersion lens into place. Focus carefully, preferably by observing the
lens itself while bringing it as close to the cover slip as possible, then
focusing by moving the lens away from the specimen. When in focus the lens
nearly touches the cover slip. The focal plane is so narrow that it is very
easy to focus right past it. If you are focusing toward the specimen, you can
drive the lens right into it.
In a wet mount, the specimen is placed in a drop of
water or other liquid held between the slide and the cover slip by surface
tension. This method is commonly used, for example, to view microscopic
organisms that grow in pond water or other liquid media, especially when
studying their movement and behavior. It is also used to examine physiological
liquids like blood, urine, saliva, semen, and vaginal discharge. Care must be
taken to exclude air bubbles that would interfere with the viewing and hamper
the organisms' movements. For pathological and biological research, the
specimen usually undergoes a complex histological preparation that may involve
cutting it into very thin sections with a microtome, fixing it to prevent
decay, removing any water contained in it, staining specific parts of it, and
impregnating or infiltrating it with some transparent solid substance. As part
of this process the specimen usually ends up firmly attached to the slide.
REFERENCEShttp://faculty.fmcc.suny.edu/mcdarby/Pages/Lab%20Exercises/MICINTRO.htm
Campbell Biology (9th
Edition),Jane B. Reece (Author), Lisa A. Urry (Author), Michael L. Cain
(Author), Steven A. Wasserman
(Author), Peter V. Minorsky (Author), Robert B. Jackson (Author),2011
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