Medical microbiology CLS 212

Introduction What is microbiology? the branch of biology that studies microorganisms and their effects on humans Microorganisms a collection of organisms that share the characteristic of being visible only with a microscope contribute to the quality of human life o maintain the balance of chemical elements in nature o breakdown the remains of all that die o recycle carbon, nitrogen, sulfur, phosphorus and other elements some cause infectious disease called Pathogenic o overwhelm body systems by sheer force of numbers o produce powerful toxins that interfere with body physiology o viruses inflict damage by replicating themselves within tissue cells causing tissue degeneration

Classification of Microorganisms Taxonomy - the science of classification Kingdom (5 major divisions) Phylum (groups of related Classes) Class (groups of related Orders) Order (groups of related Families) Family (groups of related Genera) Genus (groups of related Species) Species (living organisms that are alike) The Five Kingdoms 1. Monera (unicellular prokaryotes: bacteria, cyanobacteria, blue-green algae) 2. Protista (unicellular eukaryotes: protozoa, unicellular algae, slime molds) 3. Fungi (multicellular eukaryotes: molds, mushrooms, yeasts) 4. Plantae (multicellular eukaryotes: plants) 5. Animalia (multicellular eukaryotes: animals) Species a population of individuals that breed among themselves microorganisms that are 70% similar from a biochemical standpoint

Classification of Microorganisms Microorganisms and all other living organisms are classified as Prokaryotes and Eukaryotes. They are distinguished on the basis of their cellular characteristics. Prokaryotes and Eukaryotes enclosed by cell (plasma) membranes use DNA for genetic information Prokaryotes lack a nucleus lack organelles include bacteria and cyanobacteria (blue-green algae) Eukaryotes have a nucleus have organelles include fungi, protozoa and simple algae Viruses are neither Prokaryotes or Eukaryotes lack the characteristics of living things are able to replicate only in their host (living cells)

Historical Background mid 1600s – English scientist Robert Hooke viewed cells and observed strands of fungi 1670s – Dutch merchant Anton van Leeuwenhook made a simple one-lens microscope and observed and provided accurate descriptions of protozoa, fungi and bacteria – Carolus Linnaeus classified all known plants and animals and set down rules for classification – The Golden Age of Microbiology

Historical Theories The Theory of Spontaneous Generation a long-held theory that life springs up from non-living or decaying organic matter, was based on observations of rotting food seemingly producing living organisms. Francesco Redi ( ) was an Italian physician who showed that rotting meat carefully kept from flies will not spontaneously produce maggots.Francesco Redi The germ theory 1861: Louis Pasteur'sLouis Pasteur's famous experiments with swan-necked flasks finally proved that microorganisms do not arise by spontaneous generation This led to: Development of sterilizationsterilization

Historical Theories Koch’s postulates 1890s: Robert Koch sets guidelines for how to prove that a particular microbial agent is responsible for a particular disease. Koch's postulates state that: The suspect microorganism must be routinely isolated from patients with a particular illness; The microorganism must be grown in pure culture in vitro; When the pure culture is inoculated into a new host, it must cause the same illness; The same microorganisms must be reisolated from new host.