Microbiology and parasitology

• Types of microscope


  • Simple microscope
  • Compound microscope
  • Electron microscope
  • Stereomicroscope
  • Scanning probe microscope
• Simple microscope


  • Uses a single lens for the magnification of the sample
  • Is a convex lens with a small focal length
• Compound microscope


  • Has more than one lens
  • Has a combination of lenses and 2 optical parts known as an objective lens and an eyepiece or ocular lens
• Electron microscope


  • The source of illumination is the beam of accelerated electrons
  • Special type of microscope with high resolution of images
  • Images can be magnified in nanometers
• Types of electron microscope

  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
• Stereo microscope


  • Provides 3D view of a specimen
  • Also known as dissecting microscope
  • There are separated objective lens and eyepiece such that there are 2 separate optical parts for each eye
• Scanning probe microscope


  • Finds application in industries where the examination of the specimen is done at the nanoscale levels
  • Study of a specimen's properties, its reaction time, and its behavior when stimulated can be done with the help of a scanning probe microscope
• In preparing the specimen to be observed, you need slides and cover slips. The standard slides used in school are made of glass.
• The thickness of the glass slides is 1.0- 1.2 mm. Cover slips are more fragile but can be reused if handled with extreme care.
• The cover slips are square shaped, with sides having a standard of 18 or 20 mm. The thickness varies depending on use, but they are usually 0.17 to 0.25 thick.
• If you are working on oil immersion or high resolution, coverslips with a thickness of 0.13-0.17 mm are recommended.
• Wet mount slide preparation

  1. Put a small amount of water/oil on the slides

  2. Place the specimen using the forceps

  3. Place the coverslip at a 45 degree angle on top of the specimen
• Carrying the microscope


  One hand should hold the arm of the microscope and the other hand should act as support on the base
• Initial focusing of the sample specimen

  1. Rotate the revolving nosepiece until the desired objective lens is in position

  2. Put the glass slide with the sample specimen on the stage and use the stage clips to secure it

  3. Turn the coarse adjustment knob until there is enough distance between the sample and the objective lens
• Fine focusing of the sample

  1. Regulate the amount of light entering the sample by opening the diaphragm

  2. Look through the eyepiece with both eyes open

  3. Use the fine adjustment knob to focus the specimen even more
• Cleaning the microscope before storing

  1. Clean the objective lenses with an approved solution and lint free cloth

  2. Rotate the nosepiece to the lowest power objective
• Proper storage of the microscope

  1. Ensure the mirror is secured in place

  2. Unplug the microscope if it has an electronic switch

  3. Check if the removable parts are complete

  4. Cover the microscope to prevent dust
• Microbiology


  The study of microbes
• Major groups of microorganisms

  • Acellular (prions, viruses)
  • Cellular (prokaryotes - archaea, bacteria; eukaryotes - algae, fungi, protozoa)
• Virus


  Considered a non-living thing, lacks necessary cellular parts to replicate independently, relies on host cell machinery
• Hypotheses on the origin of viruses

  • Reduction hypothesis (regressive hypothesis)
  • Escape hypothesis (progressive hypothesis)
  • Virus-first hypothesis
• Microbes in our lives

  • Majority help maintain balance of life in the environment
  • Adult human has 40 trillion bacterial cells (500-1000 species)
  • Help in digestion, reproductive health, vitamin synthesis
  • Small minority are disease-causing pathogens
• Pathogens/infectious agents


  Disease-causing microorganisms
• Infectious disease


  Results when pathogens colonize the body and cause disease
• Microbial intoxication


  Results when a person ingests a toxin produced by a microbe
• Non-pathogens


  Microbes that do not cause disease, some are beneficial, others have no effect
• Opportunistic pathogens


  Microbes that colonize our bodies but have the potential to cause disease if they gain access to the wrong part of the body
• Why study microbiology


  • Microbes act as saprophytes/decomposers essential for maintaining ecosystems
  • Used in bioremediation to clean up industrial waste
  • Involved in elemental cycles
  • Essential in biotechnology and industries
  • Sources of antimicrobial agents like antibiotics
  • Helps understand disease and develop vaccines
  • Relevant for understanding emerging diseases and antibiotic resistance
  • Essential in genetic engineering
• The first microorganisms on Earth were likely Archaea and Cyanobacteria, which appeared around 3.5 billion years ago.
• Human pathogens have existed for thousands of years and were observed in the bones and internal organs of mummies and early human fossils.
• Microbiologists


  Have engineered bacteria and yeasts to produce a variety of useful substances, such as insulin, various types of growth hormones, interferons, and materials for use as vaccines
• Earth existed about 4.5 billion years ago
• For the first 800 million to 1 billion years of earth's existence, there was no life on this planet
• Fossils of primitive microorganisms were found in ancient rock formation 3.5 billion years ago
• Animals appeared on earth 900 and 650 million years ago
• Humans (Homo-sapiens) have existed 100,000 years or so
• Candidates for first microorganisms

  • Archaea
  • Cyanobacteria
• Human pathogens have existed for thousands of years and were observed in the bones and internal organs of mummies and early human fossils
• Bacterial diseases, such as tuberculosis, leprosy, and syphilis, malaria, hepatitis, and parasitic worm infections, such as schistosomiasis, dracunculiasis (guinea worm infection), hookworm, and fluke and tapeworm infections, have been around for a very long time
• The earliest known account of a "pestilence" occurred in Egypt


  3180 BC