INTRODUCTION TO MICROBIOLOGY

• Definition of Microbiology:

  • Study of organisms and agents too small to be seen clearly by the unaided eye
  • Study of microorganisms
• Microorganisms are categorized into two groups:

  • Cellular (prokaryotes: bacteria, cyanobacteria, archaeans; eukaryotes: fungi, protozoa, algae)
  • Acellular (viruses)
• Importance of Microbiology:

  • Microbes perform a range of functions in everyday life and industries
  • Microorganisms are sources of antimicrobial agents and decomposers
  • Microbiology plays a role in disease management and faces challenges like antibiotic resistance
• Discovery of Microorganisms:

  • Francesco Stelluti made the earliest microscopic observations in 1625-1630
  • Robert Hooke published the first drawing of a microorganism in 1665
  • Antony van Leeuwenhoek made extensive, accurate observations of microorganisms
• Theory of Spontaneous Generation:

  • People believed in spontaneous generation, challenged by Francesco Redi
  • Lazzaro Spallanzani improved on Redi's experiments
  • Louis Pasteur disproved spontaneous generation with the germ theory
  • John Tyndall demonstrated that dust carries germs
• Golden Age of Microbiology:

  • Pasteur's work ushered in the Golden Age
  • Disease-causing microbes were discovered
  • Techniques for isolating and characterizing microbes were improved
  • Robert Koch demonstrated the role of bacteria in causing disease and developed Koch's postulates
• Koch isolated suspected bacterial pathogens in pure culture, containing only one type of microorganism
• Koch initially cultured bacteria on cut, boiled potatoes, but later developed culture media using meat extracts and protein digests
• Fannie Eilshemius Hesse suggested the use of agar as a solidifying agent for culture media
• Koch and his associates developed media such as nutrient broth and nutrient agar
• Richard Petri developed the petri dish for holding solidified media in Koch's laboratory
• Pasteur and Roux discovered that incubating cultures for long intervals attenuated bacteria, making them lose their ability to cause disease
• Attenuated cultures were used as vaccines to protect against diseases
• Pasteur prepared rabies vaccine by growing the pathogen in an abnormal host, the rabbit
• Emil von Behring and Shibasaburo Kitasato injected inactivated toxin into rabbits to produce antitoxins for diphtheria and tetanus
• Elie Metchnikoff discovered phagocytes and phagocytosis in blood cells
• Industrial microbiology developed from Pasteur's work on alcoholic fermentations
• Microbial ecology studies the ecological role of microorganisms in carbon, nitrogen, and sulfur cycles
• Martinus Beijerinck isolated nitrogen-fixing bacteria like Azotobacter and sulfate-reducing bacteria
• Microbiology has basic divisions like bacteriology, mycology, protozoology, immunology, virology, nematology, and applied aspects for practical problems
• Major fields of microbiology include medical microbiologists, public health microbiologists, immunologists, agricultural microbiologists, microbial ecologists, food and dairy microbiologists, and industrial microbiologists
• Microbiologists study microbial physiology, biochemistry, genetics, and molecular biology to understand genetic information and its regulation in cells and organisms