Topic: Environment

Last updated: May 21, 2019

OBJECTIVE : To identify all the parts of a compound microscope. Then, know how to correctly use the microscope , especially the oil immersion lens and wet mounts. The last objective is to understand how microorganism can be measured under the light microscope.

METHOD :A.Using the microscope

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B. All the prepared demonstration slides were observed.

C. Wet mount of baker’s yeasts Saccharomyces cerevisiae was prepared.

Staphylococcus aureus Gram-positive bacteria
Spherical shape
Cells occur singly or in pair
Non motile
Size 0.8µm
Escherichia coli Gram-negative bacteria
Rod shape
May have pili to move and attach to human cell
Aproximately 0.5 ?m in width by 2 ?m in length
Facultative anaerobe bacteria
Salmonella typhi Gram-negative
Rod shape
Aerobic and facultative anaerobic
2.0-4.0 X 0.6µm in size
Streptococcus sp Gram-positive
Arranged in chain
Non motile
Spherical shape
0.5 – 2.0µm in diameter
Bacillus subtilis Gram- positive
Rod shape
Aerobic or facultative anaerobic
4-10 µm long and 0.25-1.0 µm in diameter
Rhizopus sp Unbranched
Best growth in 45°C
Umbrella-like structure
Kingdom fungi
Penicillium sp Molecule that is used as an antibiotic
Kingdom fungi
Simple or branched
Brush like
Aspergillus sp Unbranched structure
Pores forming
Septate hyphae (2.5-8.0µm)
Mucor sp Best growth ;37°
Can be simple or branched
Form apical,globular sporangia that aresupported and elevated by a column shaped columnellaCandida albican Unicellular
Oval shape diploid fungus
Responsible for candidiasis in humans host
Bacillus megaterium Rod shaped
Can live in extreme environment
Aerobic spore forming
Gram positive
Found in soil
Proteus vulgaris Rod shaped
Gram negative
Inhibit intestinal tract
Clostridium botulinum Gram positive
Rod shaped bacterium that produce several toxin
Obligate anaerobe
Haemophilus influenza Gram negative
Pleomorphic in shape
Non motile
1C) Saccharomyces cerevisiae
unicellular eukaryotic fungi
globular,oval or elongated shaped
a species of yeast
10 µm in size
Microscope is the instrument that produces enlarged images of small objects where it is impossible to see with naked eye. In this experiment (1A), the type of microscope use is light microscope. To observed all the prepared slide given, we observed under four types of magnification power which is 4x, 10x, 40x and 100x. We start to observed the slide by using 4x magnification increasing order until 100x magnification. Then, we followed the step to used the microscope by the method given.

For 100x magnification, we need to put a drop of oil between the lens and slide cover. Oil immersion is the technique of using a drop of oil to wet the top of the slide cover and the front of the objective lens. This effectively immerses or bathes the light path between the lens and object viewed, allowing finer details to be seen.

Next, we have been observed all the demonstration slide given for bacteria and fungi. For the bacteria is, Staphylococcus aureus, Escherichia coli, Salmonella typhi, Streptococcus sp and Bacillus subtilis. All of these bacteria are we have been given all the description and size of each bacteria based on their characteristics in the result table. For the example one of the bacteria is Staphylococcus aureus which is gram-positive bacteria with spherical shape and the size is 0.8µm. Then, for the fungi we observed is Rhizopus sp, Penicillium sp, Aspergillus sp, Mucor sp, Candida albican, Bacillus megatrium, Proteus vulgaris , Clostridium botulinum and Haemophilus influenza. Same as the bacteria, all of these fungi we have been given the description.

Lastly, we were prepared a wet mount of baker’s yeast of Saccharomyces cerevisiae and observed it under microscope and identify its approximate size which is 10µm.

Based on the experiment, we were able to identify all parts of a compound on microscope likes fine focus knob, slide holder, objective lens and many more. Then we also know how to use the microscope correctly with correct technique to handle it, especially the oil immersion lens and wet mounts. Last part for objective 1 , we were able to understand on how microorganisms can be measured under the light microscope which is used in part C to measured the size of Saccharomyces cerevisiae.
Why is oil necessary when using the 90X to 100X objective?
To get clearer image because of more light is directed through the objective lens with refractive index equal to glass slide.

In the prepared slides, which organism was the largest?
Saccharomyces cerevisiae is the largest organism that I observed
When identify microorganisms,why should a wet mount be used when making measurement?
In this experiment, wet mount should be use to moisture based specimen


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