micro part 1

• Branches of microbiology


  • Bacteriology
  • Protozoology
  • Mycology
  • Virology

  
• Bacteriology


  The study of prokaryotes that include Bacteria and Archaea (archaea are nearer to eukaryotes than bacteria)

  
• Protozoology


  The study of protists that include Protozoa and Algae

  
• Mycology


  The study of fungi that include Yeasts and Molds
• Virology


  The study of viruses
• All living beings are divided into 2 large groups: animals and plants. This is false.
• Cellular organisms are divided into three domains

  • Bacteria
  • Archea
  • Eukarya (includes all eukaryotic organisms)
• Prokaryotes (bacteria + archea) represent the most abundant form of life on earth
• Single prokaryotic cells are not visible by naked eyes however we can see aggregations of microorganisms such as microbial mats composed of stratified microorganisms of different species
• Huge amass of prokaryotes are colorful due to different pigments
• Prokaryotes represent the largest share of Earth's biomass
• There are an estimated 100 billion stars in the Milky Way, while the total number of prokaryotes on Earth is 5 · 10^30
• Reasons why microorganisms are so abundant on Earth

  • They replicate very quickly
  • They have different metabolisms that allow them to live in different ecological habitats
  • They are required to recycle materials
• Ecological roles of microorganisms

  • Decomposers of dead organisms
  • Oxygen producers (cyanobacteria do photosynthesis and release oxygen)
  • Nitrogen fixers (transform atmospheric nitrogen into chemical nitrogen that can be assimilated)
• The existence of microorganisms had already been intuited by Marco Terenzio Varrone (116-27 BC) in the first century BC
• Varrone: '"...animalia quaedam minuta, quae non possunt oculi consequi, et per aera intus in corpus per os ac nares perveniunt atque efficiunt difficilis morbos…"'
• Varrone's intuition was not taken into account because at that time the theory of MIASMI (not well specified harmful influences) prevailed
• Microscope


  Invented by Robert Koch, used by merchants to evaluate product quality
• Types of microscopes


  • Light microscope
  • Electron microscope
• Resolution


  The minimum distance at which two distinct points of a specimen can be clearly distinguished
• Light microscope


  Has a resolution of 0.2 μm, routinely used to examine both stained and unstained specimens, forms a dark image against a lighter background
• Types of light microscopes

  • Dark-Field Microscope
  • Phase-Contrast Microscope
  • Differential Interference Contrast Microscope
  • Fluorescence Microscope
  • Confocal Microscopy
• Electron microscope


  Has a resolution of 0.5 μm, uses beams of electrons to create highly magnified images
• Types of electron microscopes

  • Transmission Electron Microscope (TEM)
  • Scanning Electron Microscope (SEM)
• Viruses are very small, they need to enter eukaryotic cells to replicate themselves
• Many pathogens of a bacterial nature penetrate our eukaryotic cells, in this way they can escape the immune defenses (antibodies do not act inside the cells)
• Prokaryote morphologies


  • Cocci (roughly spherical cells)
  • Rods (bacilli, differ in length-to-width ratio, have helical morphology)
  • Vibrions (comma-shaped)
  • Spirilla (rigid, spiral-shaped cells with tufts of flagella)
  • Spirochetes (flexible, spiral-shaped bacteria with unique internal flagellar arrangement)

  
• Cocci


  • Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus

  
• Rods


  • Bacillus subtilis, Bacillus cereus, Bacillus anthracis
• Vibrions


  • Vibrio cholerae
• Spirilla


  • Spirillum volutans
• Spirochetes


  • Leptospira, Treponema pallidum, Borrelia burgdorferi
• Other prokaryotes may also have other morphologies like thin and filamentous or have appendages (Stalk and Hypha)
• Many actinobacteria (gram-positive bacteria) form long filaments called hyphae that form a network called mycelium

  
• Taxonomy of selected prokaryotes

  • Genus: Leptospira, Family: Leptospiraceae, Phylum: Spirochetes
  • Genus: Borrelia, Family: Spirochaetaceae, Phylum: Spirochaete
  • Genus: Treponema, Family: Spirochaetaceae, Phylum: Spirochaetes
• Other prokaryote morphologies


  • Square-shaped bacteria of Walsby
  • Caulobacter crescentus (Stalked bacterium)
  • Streptomyces (filamentous bacteria)

  
• Division patterns in cocci

  • Diplococcus (pairs)
  • Streptococcus (long chains)
  • Micrococcus (tetrads)
  • Sarcina (cubical packets of 8)
  • Staphylococcus (irregular, grape-like clusters)

  
• Bacillary shaped cells have various morphologies, some species have a tendency to remain partially associated with each other even after division, coccobacilli have a cell body with a morphology between spherical and bacillus

  
• Cocci and bacilli


  • Streptococcus pneumoniae (diplococcus), Staphylococcus aureus, Streptococcus pyogenes, Bacillus megaterium, Micrococcus lutens

  
• The size of bacteria is usually between 0.2 μm and 7.0 μm, but there are exceptions like cyanobacteria Oscillatoria, Epulopiscium fishelsoni, and Thiomargarita magnifica (the largest bacterium discovered so far, up to 2 cm long)