History

• Microorganisms are considered transitional forms of either the plant or animal kingdom
• Kingdom Protista/Protists consist of unicellular microorganisms like viruses, bacteria, fungi, protists, and algae
• There are 2 classes of protists:

  • Higher Protists (Eukaryotes) include algae, protozoa, fungi, and molds
  • Lower Protists (Prokaryotes) include bacteria and viruses
• Microbiology is the study of very small living organisms that can only be viewed under a microscope, including fungi, bacteria, algae, and protists
• Binary fission is the reproduction of a cell by division into 2 approximately equal parts, a mode of reproduction for bacteria
• Bacteria are unicellular microorganisms with shapes like spherical, round, or spiral forms, moving via flagella, and have an average size of 0.2-5.0 microns
• The cell wall of bacteria is made up of peptidoglycans
• Fungi are heterotrophic microorganisms requiring organic compounds for metabolic synthesis, classified in a kingdom called thallophyta, with a cell wall made of chitin
• Protozoa are eukaryotic microorganisms like amoeba and algae, abundant in ponds and fresh water, with algae being photosynthetic eukaryotes having a cell wall made of cellulose
• Viruses are the smallest of cell microorganisms, ultramicroscopic and intracellular parasites, with DNA or RNA genomes surrounded by a capsid and an additional outer membrane called an envelope
• Bacteriophages are viruses that infect and parasitize bacteria
• Robert Hooke (1665) discovered the cell theory, reporting that the smallest life units are cells, marking the beginning of the cell theory
• Anton van Leeuwenhoek (1673) was the first to view living cells using a simple microscope, observing microorganisms through magnifying lenses and calling them "animalcules"
• Francesco Redi (1668):

  • Italian physician
  • Demonstrated that maggots arise spontaneously from decaying meat
  • Maggots can only arise if they enter the jar
  • Conducted an experiment with 3 jars containing meat
• John Needham (1745):

  • English scientist
  • Claimed microorganisms could arise spontaneously from heated nutrient broth
  • Discovered that even after heating the broth, the cover did not have any microorganisms or bacteria, but if the broth was left open after heating, there were still live microorganisms
• Lazzaro Spallanzani (1765):

  • Italian scientist
  • Suggested that microorganisms entered the solution due to the air
  • Repeated Needham's experiment and claimed microorganisms came from the air
• Rudolph Virchow (1858):

  • Challenged spontaneous generation with his theory of biogenesis (living cells arise from pre-existing cells)
• Louis Pasteur (1861):

  • French scientist
  • Resolved the issue of spontaneous generation by boiling broth and sealing the flask, leading to the development of Aseptic technique to prevent contamination of microorganisms present in the air
• Contributions of the Golden Age of Microbiology (1857-1914):

  • Pasteurization
  • Fermentation
  • Germ theory of disease
• Germ Theory of Disease:

  • Includes Louis Pasteur (1865) who found a way to kill silkworms
  • Agustino Bassi (1835), an amateur microscopist, proved that silkworm disease is caused by fungus
  • Joseph Lister (1860), an English surgeon, applied the germ theory to medical procedures and used carbolic acid to kill microorganisms
• Ignaz Semmelweis (1840):

  • Demonstrated how disease could be transmitted by physicians not disinfecting hands, leading to childbirth fever or Puerperal fever
• Robert Koch (1876):

  • German physician
  • Discovered the rod-shaped "Ranchi bacillus" or "Bacillus anthracis" causing anthrax
  • Developed Koch's postulates to prove that a specific microorganism causes a particular disease
• Modern Developments in Microbiology:

  • Virology: study of viruses
  • Immunology: study of immunity
  • Recombinant DNA technology
• Dmitri Ivanovsky (1892):

  • Discovered the Tobacco Mosaic Virus (TMV), the first viral pathogen
• Wendell Stanley (1935):

  • Discovered viruses made of nucleic acid and proteins
• Origins of recombinant DNA technology:

  • Molecular biology studies the mechanism where microorganisms inherit traits
  • Microbial genetics specifically studies genetic information and how DNA directs the synthesis of proteins
• James Watson and Francis Crick (1953) proposed the model for structures and replication of DNA
• Francois Jacob and Jacques Monod (1961):

  • Discovered messenger RNA
  • First to discover regulation of gene function in bacteria
• Paul Berg (1960) showed fragments of human and animal DNA attached to bacterial DNA
• Branches of microbiology:

  • General microbiology studies the classifications of microorganisms and how they function
  • Medical microbiology deals with the diseases of humans and animals
  • Public health microbiology is closely related to medical microbiology and focuses on controlling communicable diseases
  • Agricultural microbiology concerns the impact of microorganisms on agriculture
  • Microbial microbiology studies the relationships of microorganisms' habitats
  • Food and dairy microbiology studies microorganisms that inhibit, create, or contaminate food and dairy products, focusing on the prevention of microbial spoilage
  • Industrial microbiology deals with using microorganisms to make vaccines and antibiotics
  • Veterinary microbiology controls the spread of diseases in animals
  • Microbial genetics and molecular biology focus on the nature of genetic information and how it regulates the development of cell organisms
• Naming and classifying microorganisms:

  • System of nomenclature established by Carolus Linnaeus in 1735
  • Scientific names are in Latin language, traditionally used by scholars
  • Genus (italicized and capital) and species (italicized and small letters)
• Ernst Heinrich Haeckel (1886), a German zoologist, proposed the classification system between three kingdoms:

  • Plantae
  • Animalia
  • Protista
• Robert Whittaker (1969) classified systems of nomenclature based on cellular and organizational patterns of microorganisms:

  • Plantae (Ferns)
  • Animalia (Insects)
  • Fungi (yeast, mushrooms, animals, insects, and plants)
  • Protist (mold, algae, protozoa)
  • Monera (prokaryotes) – Archaea, bacteria
• Carl Woese (1977) proposed the three primary super kingdoms:

  • Bacteria (sometimes called Eubacteria)
  • Archaea
  • Eukarya