Microbiology (Part 1)

• The study of microscopic organisms


  Including viruses, prokaryotes and simple eukaryotes
• Microbiology involves:


  • Biochemistry

  • Genetics

  • Pathology

  • Immunology

  • Epidemiology
• Micro-organisms


  Are living things that are too small to see with the naked eye
• Microorganisms are important


  To the maintenance of an ecological balance on Earth
• Types of Micro-organisms:


  1. Bacteria

  2. Archaea

  3. Fungi

  4. Protozoa

  5. Algae

  6. Viruses

  7. Parasites

  8. Prions
• Prokaryotes are


  The most pervasive life form on the planet
• Prokaryotes can


  Tolerate extremes in pH, temperature, salt concentration
• Bacteria


  Decompose dead material and return chemicals to the ecosystem.
• If prokaryotes were to disappear

  Eukaryote life would not survive
• If eukaryotes were to disappear

  Prokaryotes would still exist
• Autotroph


  Organism needs only inorganic CO2 as a carbon source
• Heterotroph


  The organism requires organic nutrients as a source of carbon.
• Photoautotrophs


  Photosynthetic organisms that harness light energy to drive the synthesis of organic compounds from CO2
• Chemoautotrophs


  Need only CO2 as carbon source, but use chemical energy from oxidation of inorganic substances, such as hydrogen sulphide, ammonia, and ferrous ions.
• Photoheterotrophs


  Can use light energy to generate ATP, but must obtain their carbon in organic form.
• Chemoheterotrophs


  Must consume organic molecules for both energy and carbon.
• Another metabolic variation in prokaryotes

  Is the effect that oxygen has on their growth
• Obligate aerobes


  Use oxygen for cellular respiration and cannot grow without it
• Facultative anaerobes


  Will use oxygen if it is present, but can also grow by fermentation in an anaerobic environment.
• Obligate anaerobes


  Cannot use oxygen and are poisoned by it.
• Microaerophile


  Needs oxygen, but not at the concentration present in the atmosphere
• Aerotolerant


  Does not use oxygen and is not poisoned by oxygen
• Prokaryotes come in a variety of shapes


  Most are unicellular
• Common shapes of Prokaryotes

  Cocci, Bacilli, Spirilla
• Cocci


  Spheres are the most common shape
• Bacilli


  Rods
• Spirilla


  Spiral shaped
• Prokaryotic cells range


  From 1-5μm

  • About 10-100x smaller than eukaryotic cells
• Prokaryotes reproduce by


  Binary fission
• Binary fission


  Is the asexual reproductive process used by most prokaryotes
• Binary fission results


  In two identical cells

  • Genetic variation is derived from mutation...

  • Leads to exponential growth
• Prokaryote Motility:


  Rotating flagella aid in locomotion
• Prokaryotes use flagella


  To propel themselves forward
• About half of all prokaryotes show

  taxis
• Taxis


  Movement toward(positive) or away (negative)from a stimulus
• Three types of taxis

  Chemotaxis, Phototaxis, Magnetotaxis
• Chemotaxis


  Organisms direct their movements according to certain chemicals in their environment.

  This is important for bacteria to find food (e.g., glucose) by swimming towards the highest concentration of food molecules, or to flee from poisons.
• Phototaxis


  Organism moves in response to light stimulus

  • This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis
• Magnetotaxis


  Some organisms contain internal structures known as magnetosomes, which allow the organism to orient to the Earth's magnetic field

  • More accurately → magnetic bacteria.
• We now know that prokaryotes are classified into two domains:

  • Bacteria

  •Archaea