VMCB POTA

• Microbiology is the study of living organisms of microscopic size
• Microbe


  Term first used by Sedillot (1878), now commonly replaced by microorganisms
• Timeline of emergence of life on Earth

  • Formation of Earth, estimated to be 4.6 billion years ago
  • Emergence of primitive forms of life which had no dependence on oxygen, 4 billion years ago
  • Organisms resembling primitive bacteria, 3.5 billion years ago
  • Cyanobacteria and related organisms, 2.5 billion years ago
  • Eukaryotic cells, 1.5 billion years ago
  • Diverse forms of early animal life, 0.5 billion years ago
  • Mammals, Present
• Lucretius (about 98-55 BC) and Girolamo Fracastoro (1478-1553) suggested that disease was caused by invisible living creatures
• Antony van Leeuwenhoek


  • He was the amateur microscopist and was the first person to observe microorganisms (1673) using a simple microscope
  • In 1683 he made accurate descriptions of various types of bacteria and communicated them to the Royal Society of London
  • Their importance in medicine and in other areas of biology came to be recognized two centuries later
• Spontaneous generation theory


  Hypothetical process by which organisms develop from nonliving matter
• Aristotle (384-322 BC) thought animal could originate from the soil
• Jean Baptiste van Helmont, 17th Century Flemish Chemist, provided a recipe for the spontaneous generation of mice
• John Needham (1745) and Felix Pouchet (1859) published experiments purporting the spontaneous generation of microorganisms
• Antonie Philips "Anton" van Leeuwenhoek


  • He developed the microscope
  • Observed a number of motile structures in fluids, not visible to the naked eye
  • Coined the term "Animalcules"-bacteria, yeast and protozoa
• Francesco Redi's Experiment


  1. Open jar - Maggots appeared

  2. Gauze-covered jar - No maggots appeared

  3. Sealed jar - No maggots appeared
• Louis Pasteur


  • Also known as Father of Microbiology
  • Effectively ended the controversy of spontaneous generation
  • If cells arise from nonliving substances, they will appear in sterile broth
• Contributions of Louis Pasteur

  • Coined the term microbiology
  • Proposed germ theory of disease
  • Disapproved theory of spontaneous generation
  • Developed sterilization techniques
  • Developed methods and techniques for cultivation of microorganisms
  • Studies on pebrine (silk worm disease), anthrax, chicken cholera and hydrophobia
  • Pasteurization
  • Coined the term vaccine
  • Discovery of attenuation and chicken cholera vaccine
  • Developed live attenuated anthrax vaccine
  • Developed rabies vaccine
  • Noticed Pneumococci
• Hieronymus Fracastorius (Girolamo Fracastoro) (1546) wrote "On Contagion" ("De contagione et contagiosis morbis et curatione"), the first known discussion of the phenomenon of contagious infection
• Agostino Bassi de Lodi (1835) showed that a disease affecting silkworms was caused by a fungus, the first microorganism to be recognized as a contagious agent of animal disease
• Ignaz Semmelweiss (1818-1865) decided that doctors in Vienna hospitals were spreading childbed fever while delivering babies and started forcing doctors under his supervision to wash their hands before touching patients
• Both Pasteur and Koch contributed to the identification and confirmation of the causal agent of anthrax
• Pasteur demonstrated that fowl cholera, malignant edema and suppurative lesions were each associated with a specific bacterial infection
• Causative organisms of tuberculosis and typhoid fever were recognized by Koch
• Robert Koch's Postulates


  1. Postulate 1: The organism should be regularly found in the lesions of the disease

  2. Postulate 2: It should be possible to isolate the organism in pure culture from the lesions

  3. Postulate 3: Inoculation of the pure culture into suitable laboratory animals should reproduce the lesion of the disease

  4. Postulate 4: It should be possible to re-isolate the organism in pure culture from the lesions produced in the experimental animals

  5. Subsequently an additional fifth criterion introduced states that specific antibodies to the organism should be demonstrable in the serum of patients suffering from the disease
• Contributions of Robert Koch

  • Staining techniques: He described methods for the easy microscopic examination of bacteria in dried, fixed films stained with aniline dyes (1877)
  • Hanging drop method: He was the first to use hanging drop method by studying bacterial motility
  • Methods for isolating pure cultures of bacteria
  • Discoveries of the causal agents of anthrax (1876), tuberculosis (1882), and cholera (1883)
  • Koch's postulates
  • Koch's phenomenon: Koch (1890) observed that a guinea pig already infected with the bacillus responded with an exaggerated response when injected with the tubercle bacillus or its protein
• Important Discoveries by other Scientists

  • Hansen (1874) - Described the leprosy bacillus
  • Neisser (1879) - Discovered the gonococcus in the pus discharge from urethra
  • Eberth (1880)
  • Alexander Ogston (1881)
  • Loeffler (1884)
  • Nicolaier (1884)
  • Rosenbach (in 1886)
  • Fraenkel (1886)
  • Weichselbaum (1887)
  • Bruce (1887)
• Bacteria in dried, fixed films stained with aniline dyes


  Examination of (1877)
• Hanging drop method


  Used to study bacterial motility
• Methods for isolating pure cultures of bacteria

  1. Discoveries of the causal agents of anthrax (1876)

  2. Tuberculosis (1882)

  3. Cholera (1883)
• Koch's phenomenon


  Guinea pig already infected with the bacillus responded with an exaggerated response when injected with the tubercle bacillus or its protein (1890)
• Robert Koch (1843-1910)
• Important Discoveries by other Scientists

  • Hansen (1874) - Described the leprosy bacillus
  • Neisser (1879) - Discovered the gonococcus in the pus discharge from urethra
  • Eberth (1880) - Observed the typhoid bacillus
  • Alexander Ogston (1881) - Described the staphylococci in abscess and suppurative lesions
  • Loeffler (1884) - Observed and described the diphtheria bacillus
  • Nicolaier (1884) - Observed the tetanus bacillus in soil
  • Rosenbach (in 1886) - Demonstrated the tetanus bacillus with round terminal spore
  • Fraenkel (1886) - Described the pneumococcus
  • Weichselbaum (1887) - Described and isolated the meningococcus from the spinal fluid of a patient
  • Bruce (1887) - Identified the causative agent of malta fever
  • Schaudin and Hoffman (1905) - Discovered the syphilis
• Whittaker's system recognizes five kingdoms of living things - Monera (bacteria), Protista, Fungi, Plantae, and Animalia
• Microorganisms are a heterogeneous group of several distinct classes of living beings
• Three domains, or Super kingdoms system

  • The Bacteria
  • The Archaea (meaning ancient)
  • The Eukarya
• Eukaryotes


  Cells possessing true nuclei containing chromosomes, replicating by mitosis, contains organelles (e.g. mitochondria, Golgi apparatus, lysosomes, ribosomes)
• Prokaryotes


  Lack true membrane-bound nuclei, circular chromosome, plasmids
• Common Features of Eukaryotes and Prokaryotes

  • DNA- the genetic material
  • Plasma membrane- a phospholipid bilayer
  • Cytoplasm- a fluid portion called the cytosol
  • Ribosomes- protein synthesis takes place
• Prokaryotic cell is generally small (1-10 μm), Eukaryotic cell is generally large (5-100 μm)
• Prokaryotic cell has DNA with nonhistone protein; genome in nucleoid, not surrounded by membrane, Eukaryotic cell has DNA complexed with histone and nonhistone proteins in chromosomes; chromosomes in nucleus with membranous envelope
• Prokaryotic cell has fission or budding; no mitosis, Eukaryotic cell has mitosis, including mitotic spindle; centrioles in many species
• Prokaryotic cell lacks membrane-bounded organelles, Eukaryotic cell has mitochondria, chloroplasts (in plants, some algae), endoplasmic reticulum, Golgi complexes, lysosomes (in animals), etc.
• Prokaryotic cell has absorption; some photosynthesis, Eukaryotic cell has absorption, ingestion; photosynthesis in some species
• Prokaryotic cell has no mitochondria; oxidative enzymes bound to plasma membrane; great variation in metabolic pattern, Eukaryotic cell has oxidative enzymes packaged in mitochondria; more unified pattern of oxidative metabolism