BIOMED SCIE Lecture 11

• Microbiology


  The study of microorganisms
• Types of Microorganisms

  • Bacteria
  • Fungus
  • Virus
  • Parasite
• Human Microbiome


  The collection of bacteria, viruses, and fungi that live in and on the human body
• There are 10 times more bacterial cells in our body than human cells
• The majority of these microbes live in our gastrointestinal tract
• Microbiome


  • It is a personalised organ
  • It has ~3.9 million genes (20,000 in human genome)
  • Human genes variation: ~0.1%
  • Human microbiome variation: up to 50%
  • ~1.2 kg bacteria in gut
• Beneficial Biological Functions of Microbes

  • Digestion: Microorganisms in digestive tract are essential for digestion and vitamin synthesis
  • Medicine: Antibiotics and other drugs can be naturally synthesised by microbes
• Primary Pathogens


  Cause disease upon infection, not normally associated with host
• Opportunistic Pathogens


  Cause disease under certain circumstances, can be part of normal flora
• Oxygen based metabolism makes a huge difference to energy production and evolution of life
• Domains of Life


  • Prokaryotes
  • Eukaryotes
  • Archaea
• Types of Microorganism


  • Prokaryotic microorganisms: Bacteria, archaea
  • Eukaryotic microorganisms: Fungi, protozoa, algae
  • Non-cellular microorganisms: Viruses
• Microbial Diversity


  • Microbial cells differ in size, shape (morphology), metabolism (physiology), motility, virulence, environmental adaptability
  • All pathogenic (disease causing) prokaryotes are bacteria
  • However the vast majority of bacteria (99%) are non-pathogenic
• Microbiology is an important medical discipline for prevention and treatment of infectious disease
• RTI, diarrhoeal diseases are principal causes of death worldwide
• Drug resistance is a major problem
• Emerging infections in immunocompromised patients
• Hospital-acquired infections
• Antony van Leeuwenhoek


  Cloth merchant in Holland who used a magnifying glass to inspect quality of cloth, developed into an amateur microscope builder and discovered "wee animalcules"
• Leeuwenhoek did not invent microscopes, but his skill in grinding and polishing lenses achieved 200X magnification, making him the "Father of Microscopy"
• Spontaneous Generation


  Living things produced from vital forces in non-living or decomposing matter
• biogenesis

  Organisms arose from seeds or germs that had entered the food from the air
• Biogenesis


  Organisms arose from pre-existing living organisms
• Pasteur's experiments


  Showed that food treated to destroy microorganisms would not putrefy, and that re-growth in previously sterile media was due to contamination from the ubiquitous presence of microbes
• Sterilisation


  The process of killing all bacteria and other microorganisms in or on objects
• Germ Theory of Disease


  One microbe causes one specific disease
• Koch's postulates


  • The microorganism must be easily found in all organisms suffering from the disease, but not in healthy organisms.
  • The microorganism must be isolated and grown in pure culture.
  • The cultured microorganism should cause disease when introduced into a healthy organism.
  • The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
• Chemotherapy


  Treatment of a disease by using a chemical substance, where the chemical must be more poisonous to the microbe than the host
• Antibiotics


  Produced naturally by fungi and bacteria
• Paul Ehrlich


  Searched for a "magic bullet" and discovered salvarsan, an arsenic derivative, was effective against syphilis
• Alexander Fleming


  Discovered that penicillin produced by the mold Penicillium notatum was able to prevent microbial growth
• Penicillin was not mass produced until the 1940s, launching the "Antibiotics Era"
• Bacterial Immune Systems


  Bacteria use enzymes which can target specific sequences (restriction enzymes) or use systems that can be directed against specific sequences like CRISPR
• CRISPR-Cas9


  A bacterial immune system discovered by Emmanuelle Charpentier and Jennifer Doudna
• Microbiology is the study of single cell organisms which make up the vast majority of the biodiversity on the earth
• From van Leeuwenheuk to Pasteur to Koch we have developed a clear understanding that microorganisms are the causative agent in many diseases
• Infection biology is studying how these microorganisms cause disease
• Quinine: First known chemical to treat a disease (malaria). Used by Spanish conquistadors.
• Oxygen available as an electron carrier• Much greater potential for energy than in the anoxic environment• Ozone layer protects from UV allowing for more stable DNA
• Microbiome plays roles in– (a) nutrition– (b) development– (c) immunity– (d) behaviour– (e) protection against harmful bacteria