Micro - Organisms

• Bacteria:

  • Bacteria are typically 1-2µm (micrometres) long. ​
  • Usually roughly cylindrical shaped. Other shapes are rod, spiral and cocci.​
  • They do not have membrane-bound organelles (prokaryotic)
  • Prokaryotic organisms​
  • Smallest and simplest lifeforms​
  • Unicellular (one-celled)​
  • Cell walls made of murein (not cellulose)
• Fungus:

  • Fungi are eukaryotic organisms – They have chromosomes contained within the nucleus and other membrane-bound organelles.
  • Yeast cells are bigger than bacteria – in the range of 4-12µm ​
  • Yeast is used in fermentation to produce ethanol.
  • Non-photosynthetic due to lack of chlorophyll​
  • Mushroom feed saprophytically by secreting enzymes to digest organic materials outside their bodies and then absorb products of digestion
  • Reproduction is sexual or asexual​
  • Unicellular or filamentous​
• Protist:

  Diverse eukaryotic cells - may share certain morphological and physiological characteristics with animals or plants or both.​

  Predominantly unicellular - few protists are multicellular.​

  Examples:​

  • Protozoa, the animal-like protists​
  • Algae, the plant-like protists​
  • slime molds and water molds, the fungus
  • Highly organized nucleus and cellular organelles​
  • Some protist possess a locomotory organ (flagella or cilia)​
  • Reside in water, damp terrestrial environments, or sometimes as parasites (eg., Trypanosoma protozoa)​
  • Can be autotrophic or heterotrophic or symbiotic in nature.
• Virus:

  Acellular (they are not made of cells) and do not contain organelles in the way that prokaryotes and eukaryotes do. ​

  They consist of genetic material (DNA and RNA) surrounded by a protein coat. ​

  Sometimes the protein coat is surrounded by an envelope of lipid bilayer and glycoproteins that originated from the cell in which the virus replicated.

  virus cannot replicate alone; it must infect cells and use components of the host cell to make copies of itself.​

  can infect humans, plants, animals, bacteria and fungi. Each one infects only specific types of hosts.​
• Prions:

  • virus-like organisms made up of a prion protein.​
  • ​ type of protein that can cause disease in animals and humans by triggering normally healthy proteins in the brain to fold abnormally.​
  • Once a misfolded prion enters a healthy person – potentially by eating infected food – it converts correctly-folded proteins into the disease-associated form.​
  • Prions attack nerve cells producing neurodegenerative brain disease. 
• Parasites:

  Parasites range from 1-10µm.​

  ​

  A parasite is an organism that lives on or in another organism at the expense of that organism. ​

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  This includes multicellular organism such as parasitic plants (mistletoe) and flatworms (tapeworms)​

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  Single-celled organisms like plasmodium (malaria) 
• Light Microscope:

  They are relatively easy to use, although they must be used with care to avid damage. ​

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  Can be used to exam plants and animal tissue. The can examine living micro-organisms as long as they are not too small.
• Scanning In a scanning electron microscope (SEM), the beam of electron is scanned across the surface of the sample. The electrons bounce off the surface and a computer is used to build up a 3D image of the surface of the sample. ​

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  The SEM shows more surface detail than is possible with a light microscope. 
• Transmission electron microscope

  In a transmission electron microscope (TEM) the electrons pass through the sample in the same way light rays pass through samples in a light microscope. This means that the TEM shows a 2D image.​

  Very thin sections of the sample are required as the electrons cannot penetrate materials very deeply. ​

  A series of thin sections can be used to take multiple 2D images that can be assembled into a 3D image
• Direct transmission:

  • Physical contact with an infected person (skin-to-skin)
  • Airborne: Pathogen is carried by dust or droplets in the air
  • Sharing of needles: transmission of blood-borne pathogens. HIV or hepatitis C virus can be spread by transfusion with contaminated blood or blood products
  • Contact with contaminated surface​ (door handle or other hard surface)
  • Unprotected sex can lead to STIs
• Indirect transmission:

  • Being bitten by an infected vector (the organism that transfers the pathogen from host to host) (malaria-mosquito)
  • Vehicle transmission occurs when infected food or water are ingested. Faecal-oral transmission. 
  • Another example of vehicle transmission from infected blood on inanimate objects such as clothing or bedding.