1. The structure and characteristics of microorganisms used in classify them
The structure and characteristics of microorganisms are used to classify them by comparing their genes of different organisms. They can be classified by placing them within Archaea, Bacteria, and Eukaryote. Microorganism shows some form of metabolism, regeneration, and reproduction. Some respond to chemical signals in their environment, which lead to new activity that involve movement. Microorganism is capable of self-propulsion, and they can undergo evolution over a period and their characteristics are transmitted to their offspring’s.
Viruses — Have no cellular structure and are classified according to their shape, type of nucleic acid, mode of replication, host organisms, and type of disease they cause.
Bacteria are single celled prokaryotic organisms. They have a cell surface membrane and a cytoplasm gel like enclosed by cell surface membrane. They have organelle an organized and specialized structure within cell. Some have hair like structure called Pilli and flagellum to propel them. They can reproduce asexually by binary fission.
Fungi are eukaryotes that lack chlorophyll and are heterotrophic. Fungi have DNA in a form of linear chromosomes inside nucleus. They can be unicellular or multicellular and are able to absorb food and secrete enzymes to digest complex molecules. Fungi grow on organisms and absorb their nutrients. Have complex cells with a nucleus and organelles. Have rigid cell walls that contain chitin. Their body is made up of filament called hyphae. They are classified based on their method of sexual reproduction.
Protozoa- Are unicellular animals like cells with a heterotrophic nutrition and have a relatively complex structure. Their body is bounded by a cell membrane and with intracellular type of digestion that can occur within the food vacuoles. Protozoa belong to the kingdom of Protista.
2. The characteristics of microorganisms used for classification
Some microorganisms are different due to their shapes, cell wall structure, and their oxygen requirement.
Bacteria — have a cell surface membrane. A cell wall made of peptidoglycan. Have no membrane bound organelles with no proper nucleus. Have a cytoplasm and have a small rings of DNA called plasmids and a large circular loop of DNA. Have smaller ribosomes than those of eukaryotic cells.
Fungi — are known as eukaryotic with their DNA in a form of linear chromosomes that are housed inside a nucleus, bound by a double membrane. It contains mitochondria. Have cell walls that contain chitin. Have hyphae, which are grown at their tips. Viruses- Have a nucleic acid type, mode of replication and host organisms. They are smaller and simpler than the prokaryotic cells. Virus contains a small amount of genetic material wrapped in a protein capsule. They cannot reproduce on their own but require a host cell to inject their DNA or RNA. They relied on the cellular machinery of the host cell to replicate the viral genetic material for it. Microorganism contains chloroplasts and carries out photosynthesis like algae. Microorganism can move and get their nutrients from environment and maintain homeostasis.
3. The use of microscope techniques to observe structures and classify microorganisms
Microscopes are used to view objects and areas that cannot be seen with the naked eye. The structure of microorganism can be examined through microscope. It consists of the unit of microorganisms that are too small to be seen by naked eye. The microscope can be used to magnify the lenses by 4, by 40 or by 100 in order to get the idea about the structure of microorganism. Microscopes employ lenses that magnify the original image. Resolution is the ability to distinguish 2 adjacent objects as distinct and separate. Magnification is to enlarge the number of times larger an image is compared to the real size of the object. Light microscopes are used to view microorganism when relatively low magnification and resolution is enough. Electron microscopes provide higher magnifications and higher resolution images. Magnification shows how bigger an image appears compared with the original object. Microscope produces linear magnification. The image appears 1000 times wider than the real size. Calculating the magnification of light microscopes, the compound microscope uses two lenses to magnify the specimen: the eyepiece and an objective lens. In most microscopes, there is a choice of objectives to use. Magnification can therefore be varied, according to the size of the specimen to be viewed and the level of detail required. The magnification of a lens is shown by a multiplication sign followed by the amount the lens magnifies. The lens magnifying ten times would be ×10. The total magnification of a microscope is magnification of the microscope = magnification of eyepiece multiple by magnification of objective.
Calculating of actual size of specimens under microscope
The eyepiece objective has a graticule in it, which has been calibrated using stage micrometers. You can be able to calculate the actual sizes of specimens from the electron micrograph by knowing the magnification. When you view an object, the scale of 100 divisions is been superimposed on it. It represents different length at different magnification and the number of scale divisions covering a specimen varies. Small scale of 1mm divided into 100 divisions is etched on it. Each division is 10 um. 1mm of the stage micrometers corresponds to 40 eyepiece divisions on the eyepiece graticule.
4. The correct set up and use of a light microscope and oil immersion lens to observe structures of microorganisms under magnification
Set up the microscope to a low power work. Place the pencil against the surface of the sub stage lamp bulb. Look down the microscope and move the pencil over the lamp until surface is seen as a blur. Use the condenser control to move it up and down until the pencil tip comes into focus. Iris diaphragm Adjust the amount of light that passes through the specimen. Make sure microscope is set up for low power work and adjust condenser. Remove the eyepiece and place it on bench and look down to see bright disc of light.
Open and close it a few times and set it diaphragm in a position where back of the lens is low power objective is two to third filled with light. Light source to shine light from a lamp that is directed on to the mirror, up through the specimen. Stage Position the slide so the specimen is over the hole on stage and clip the slide into place. Examine the slide, remove it from the microscope, and place it in a suitable disinfectant. Use of objective, coarse focus and fine focus to make your image clear of specimen make sure the slide is clipped in place on stage. Rotate the nosepiece until the lowest power objective lens clicks into place. Use the coarse focus knot to lower the objective lens as low without touching the slide. Look down the eyepiece and turn the coarse focus slowly to move the objective lens away from the slide. Continue until the specimen comes into view. Use fine focus knob and bring the specimen into focus. Move the slide gradually until part of the specimen is in the center of the field of vision. Rotate the nosepiece and bring the next higher magnification objective lens into place. Look down the eyepiece, adjust the fine focus to make a clear image of the specimen and make sure that the part you wish to view is still in the center of the field of vision. Repeat with other higher magnification until you reach the magnification. Oil immersion lens Oil immersion lenses are usually used to visualize heat fixed and stained smears. Oil immersion lenses are placed very close to the slide, in a drop of balsam oil. Spring loaded to avoid damage to the lens or the slide. Make sure the slide is dry and place one drop of immersion oil on the specimen. Place the slide on the stage and rotate the nosepiece so that the oil immersion lens is in place. Adjust the focus knob and move the oil immersion objective down as close to the slide as possible. Look down the eyepiece and adjust the fine focus knob to move the lens slowly away from the slide and keep it in the oil until the specimen comes into view and the image is clear into view. Magnification enlarges the number of times larger an image is compared to the real size of the object. Oil immersion are used to increase the light gathering ability of a lens by allowing rays emerging from the specimen at angles to be viewed. Several times in water and dry. The microorganism are so small and oil is immerse and is been check by use of microscope. Gram-positive bacteria appear purple due to primary dye crystal it retains in the cell wall and Gram negative appear pink, which retained the counter staining dye called safranin. A glass slide-containing microorganism is flooded for 2 minute with a dilute solution of a dye and raised.
5. The structures of microorganisms observed using a light microscope and an oil immersion lens
Place the specimen on a slide stage and clipped into place. Rotate the nosepiece to the lowest power of the objective lens and placed over specimen. Adjust the coarse focus knob and look into the eyepiece until the image is clear and in focus. View the image adjusts the iris diaphragm for optimum light source. Ensure the object you wish to view is directly over the hole in the stage. Rotate the nosepiece and bring the times 10 objective into place over the specimen. Look down the ocular tube and use the fine focus knob to focus the image. Use times 40 objective lens over the specimen and look down the ocular tube and use the focus knob to fine the image. The structure reveals two pattern prokaryote and eukaryotes. Eukaryotes have their DNA in a membrane-enclosed nucleus and are typically larger and structurally more complex than prokaryotic cells. Prokaryotic microorganisms have internal structure that lacks membrane-enclosed organelles. Most prokaryotes use their cytoplasmic membrane to drive energy. Oil immersion microscope is important in examining microorganism under microscope. It reduces the problems of cement drying on a lens. It allows large bright images and it is useful to study bacteria. It creates a suitable viscosity and high-resolution image.
6. The use of different microscopy techniques to observe the structures of microorganisms
Focus the real image of the object inside the microscope. Image is magnified by a second lens, which produces an inverted virtual image of the object.
Phase-contrast microscopes is use to observe unstained specimens using moving specimen such as amoeba. The microscope has a special phase-contract objectives and a condenser. The special optics of the microscope converts the differences between the transmitted light intensity. It gives clear image that appears dark against a light background.
Light microscopes are easier to move, smaller and to set up. They use electron beams of electrons. They are lighter than electron microscope. Light microscope form images including the range of wavelength provided by the light source. Have lower magnification and resolution. Able to watch living processes taking place of pond life in action.
Electron microscopes use a beam of fast travelling electrons. It has a much higher resolution than the optical microscopes. Electron microscopes produce very clear and highly magnified images. Transmission electron microscopes Specimen has to be chemically fixed by being dehydrated and stained with metal salts. The electron form two-dimensional black and white image and the photographed are called electron micrograph. Scanning electron microscope Electrons do not pass through the specimen, but cause secondary electrons to bounce off the specimen is surface and focused on a screen. It results in 3D image with magnification from 15 times up to 200,000 times. The image is black and white but computer software programs can add false color. Electron microscopes have much higher resolution than light microscopes. Electron microscopes are used in study and research in biology, medical sciences, and material science. The specimens are prepared for the appropriate type of microscope to be used for sampling. It is not possible to view any living material due to vacuum inside Electron microscopes. Electron microscopes have higher magnification and it resolution is good for measuring sizes of smaller features.