Essence, History & Taxonomy

• Microbiology studies microorganisms, including bacteria, viruses, fungi, protozoa, helminths (worms), and algae
• Microorganisms are too small to be seen with the naked eye
• A microscope is needed to view microorganisms
• Microbes help by:

  • Nutrient production and energy flow (e.g., wine, vinegar, beer, bread, yogurt, cheese)
  • Decomposition of organic waste
  • Biotechnology and genetic engineering (e.g., vaccines, antibiotics, insulin)
• Microbes harm by causing infectious diseases
• Approximately 2,000 different microbes cause diseases
• There are about 10 billion new infections per year worldwide
• There are approximately 13 million deaths from infections per year worldwide
• Historical development of Microbiology:

  • Dutch linen merchant was the first to observe living microbes
  • Sterility requires the elimination of all life forms including endospores and viruses
  • Dr. Oliver Wendell Holmes observed fewer infections in home births compared to hospital births
  • Dr. Ignaz Semmelweis correlated infections with physicians coming from autopsy rooms to maternity wards
  • Joseph Lister introduced aseptic techniques to reduce microbes in medical settings
  • Louis Pasteur and Robert Koch made significant contributions to microbiology
• Pathogens and germ theory of disease:

  • Microbes cause fermentation and spoilage
  • Disproved spontaneous generation of microorganisms
  • Developed pasteurization
  • Established Germ Theory of Disease
  • Developed a rabies vaccine
• Koch's postulates:

  • A sequence of experimental steps that verified the germ theory
  • Identified the cause of anthrax, TB, and cholera
  • Developed pure culture methods
• The Birth of Vaccination:

  • Jenner and smallpox vaccination in 1796
  • Pasteur showed how vaccinations work by creating avirulent strains of bacteria
• Modern Developments in Microbiology:

  • Bacteriology, Mycology, Parasitology, Virology, Immunology
  • Microbial genetics and molecular biology lead to Recombinant DNA Technology
  • Selected Nobel Prizes for Microbiology Research
• Taxonomy:

  • Domain: Archaea, Bacteria, Eukarya
  • Classification levels: Kingdom, Phylum, Class, Order, Family, Genus, Species
• Clinical Lab Identification methods:

  • Morphological characteristics
  • Differential staining like Gram staining and acid-fast staining
  • Biochemical tests to determine the presence of bacterial enzymes
  • Serology involving reactions of microorganisms with specific antibodies
  • Phage Typing for identifying bacterial species and strains
  • Genetics techniques like DNA fingerprinting, Ribotyping, and Polymerase chain reaction (PCR)
• Bacterial Nomenclature:

  • Each microbe has two names: Genus (always capitalized) and species (lowercase)
  • Both names are italicized or underlined
  • Examples: Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli)
• Microbial dimensions:

  • Procaryotes are measured in micrometers
  • Viruses in nanometers
  • Helminths are measured in millimeters