Assignment 17 A & B
Unit 17: microbiology and microbiological techniques
Name: Mariam Rahmeh
Student ID: 723699
Assignment title: classification of microorganisms.
, The structures and characteristics of microorganisms can be seen and classified using different
microscopes and different magnifications. When we look at medicine. Being able to recognize
differences between distinct strains of bacteria can be useful in epidemiology for tracking down
the origins or pathways of transmission and, be able to develop strategies to stop the spread of
a pathogen. These investigations can help to discover and learn more about microorganisms,
which helps scientists to explore more about how pathogens work and how they develop,
which leads to developing new treatments and strategies.
Instructions on how to use a light microscope:
Step 1: add the light microscope into the electrical socket for power source
Step2: adjust the rotating nosepiece to the objective lens with the lowest power
Step 3: cover the specimen with a coverslip or a glass cover
Step 4: use the metal clips to put the specimen to the stage
Step 5: rotate the focus coarse adjustment knob until the objective lens hangs over the slide
Step 6: move the slide until it's focused on the center and adjust the mirror for maximum light
exposure.
Step 7: when the image is focused change the coarse and fine adjustment knobs.
Step 8: Change to the next strong objective lens and adjust the focus one last time.
Step 9: and finally look over your sample.
The use of oil immersion lens
Using an oil immersion lens helps to produce high magnification images with fine focus which
will allow us to see the characteristics of microorganisms more clearly and be able to identify
them. Oil immersion is used within light microscopes. To use an oil immersion, you Place the
specimen onto the stage, slowly turn the objective lens and take it out of the visual path. After
applying immersion oil to the specimen (above the condenser lens), gently and carefully replace
the objective lens in the optical path, making sure no air bubbles enter. Royal immersion is used
in gram staining technique. Gram staining technique is used to identify whether the bacteria is
gram positive or gram negative. Royal immersion is used in gram staining to ensure a clear
imaging of the material on the slide.
,Classification
The main categories of microorganisms are viruses, bacteria, algae, yeasts, and fungi (yeasts
and Moulds). Classification is the use of definitions to tell the difference between different
types of organisms, to confirm how useful a strain is or a particular response, or to find and
recognize the pathogen. There are so many ways where a microorganism can be classified, such
as, their shape, characteristics, colour and reproduction. This is because every microorganism
has different characteristics that put them in a specific category. We can classify
microorganisms using different types of microscopes and different magnifications and
techniques to ensure a better quality and higher resolution.
Bacteria
Bacteria are single celled organisms, and there are millions of different types of bacteria. A
bacterial cell is a prokaryotic cell.
Prokaryotes:
The genetic material (DNA) is not contained in a nucleus in prokaryotes cells. Single-celled
microorganisms known as prokaryotes are found in the bacteria and archaea domains.
Prokaryotic cells lack organelles, have no nucleus, and are a lot smaller than eukaryotic cells. A
cell wall protects every prokaryotic cell. Many also include a polysaccharide-based capsule or
slime layer. Prokaryotic cells are small 0.1mm to 0.5 micrometers (μm), which is much smaller
than eukaryotic cells. They also have a single cellular DNA as genetic material and plasmid
because they lack a nucleus. (nucleus where genetic information is stored).
How can bacteria be classified under a microscope:
We can classify different types of bacteria depending on the colour they change to under a
gram stain. This is due to the differences in their cell walls which makes them stain differently
which is either gram positive or gram negative. Gram positive bacteria will appear as purple and
gram-negative bacteria will appear as red or pink. bacteria can be put into two large groups
based on the different physical properties of their cell wall. For example, gram positive bacteria
have a thick peptoglycogen wall and it will appear as purple under the gram stain whereas
other bacteria have a thin peptoglycogen wall covered by an outer membrane, stain as pink or
red which makes it gram negative.
, Fig 1: gram staining of different bacteria. A) rod-shaped gram-positive “bacillus anthracis” B)
gram stain of gram-positive cocci staphylococcus aureus (purple bits) and the gram-negative
bacilli Escherichia coli which appears as pink.
https://tmedweb.tulane.edu/pharmwiki/lib/exe/detail.php/gramstain.png?
id=bacteria_101_cell_walls_gram_staining_common_pathogens
Cell wall structures:
Gram positive bacteria have a thick peptoglycogen cell wall because it contains a mixture of
peptides and sugars. And as I have mentioned before, they will appear as purple during the
gram stain process under the microscope this is because the cell wall retains the color of the
staining technique. Gram positive bacteria do not contain an outer membrane . They can also
move around with the help of locomotion organelle like the flagella and cilia. If we look at the
image above (A) gram positive bacteria, we can see that it appears as purple/violet under the
gram stain, we can also slightly see that it looks thicker than the gram negative bacteria due to
that it has a thick peptoglycogen wall.
Gram negative bacteria has a thin layer of peptoglycogen cell wall, which can be identified
during the gram staining Process as it will appear as pink or red under the microscope. Gram
negative bacteria is surround by an outer membrane that contains lipopolysaccharide. the cell
wall also contains high amounts of lipids and it contains all types of amino acids. here we can
see the difference between gram positive and gram negative bacteria, as gram positive have
many times thicker layers of peptoglycogen and it lacks an outer membrane. If we look at the
image above (B) gram negative bacteria, we can see that it appears to be pink under the gram
stain, which helps to identify the bacteria.
