MICB Lecture 1

• Microbiology definition

  study of organisms too small to be seen by unaided eye
• Size range and microscope for viruses

  nanometers (nm) and electron microscope
• size range and microscope used for bacteria

  micrometers (um) and light microscope
• Phylogenetic tree - three domains of life

  based on sequence of small subunit ribosomal RNA genes (ssu rRNA)
• Bacteria/archaea ssu rRNA number

  16S rRNA
• Eukarya ssu rRNA number

  18S rRNA
• Bacteria features

  Members are usually single-celled, most have cell walls that contain peptidoglycan, most do not cause disease
• Archaea features

  rRNA sequences, cell walls and membrane lipids, some can generate methane gas, some found in extreme environments, do not appear to cause disease
• Eukarya

  includes plants, animals and microorganisms classified as protists/fungi
• protists

  usually unicellular, larger than bacteria and archaea
• fungi

  range from unicellular (yeasts) to multi (mold), can cause disease in humans/animals
• Prokaryotic

  includes bacteria and archaea, no membrane bound nucleus
• eukaryotic

  includes eukarya (protists/fungi), membrane bound nucleus
• viroid

  infectious agents composed of only RNA, cause many plant diseases
• satelittes

  nucleic acid enclosed in protein shell, must infect a host cell with a virus to complete life cycle, cause plant/animal diseases
• prion

  composed only of protein, responsible for neurological diseases
• Robert Hooke


  first to describe microbes (observed eukaryotic fungi), published first drawings of microorganisms
• spontaneous generation

  living organisms develop from nonliving matter, people believed this in earlier times
• Francisco Redi


  demonstrated that the presence of maggots in putrefying meat does not result from spontaneous generation but from eggs laid on the meat by flies.
• Spallanzani 


  microbes will grow in flask of meat broth, no growth if flask is sealed and boiled first, proposed that air carried germs
• Louis Pasteur


  swan-neck flask experiment: put nutrient soil in flask, then boil and leave flask exposed to air, no microbial growth resulted from this
• Picture of Experiment

  Pasteur's Experiment

  
• Joseph Lister


  surgical procedures to prevent wound infections
• Robert Koch


  first direct evidence that bacteria cause disease, studied pathogen that causes anthrax (bacillus anthracis)
• Koch's Postulates

  criteria used to establish link between a microbe and a disease

  • a microbe found in all cases of disease, absent from healthy
  • microbe must be isolated and grown in pure culture
  • same disease must result when isolated microbe inoculated into healthy host
  • same microbe must be isolated again from host
• Jenner


  material from cowpox lesions protects against smallpox, first vaccine (latin vacca means cow)
• Metchnikoff


  discovered macrophages (bacteria-englufing human cells)
• Winogradsky


  isolating bacteria that oxidizes inorganic cmpd (iron and sulfur) for energy, chemolithotrophs
• chemolithotrophs

  organisms that utilize inorganic cmpds as energy source
• Beijerinck


  isolated nitrogen fixing bacteria, reducing atmospheric N2 makes ammonia as a N source