VP_Introduction-1&2-mf.pdf

The Dawn of Microscopy Zacharias Janssen, in Middleburg, Holland, around the year 1595 The first compound microscopes produced by the Janssen's was simply a tube with lenses at each end. The magnification of these early scopes ranged from 3X to 9X, depending on the size of the diaphragm openings. A...

The Dawn of Microscopy Zacharias Janssen, in Middleburg, Holland, around the year 1595 The first compound microscopes produced by the Janssen's was simply a tube with lenses at each end. The magnification of these early scopes ranged from 3X to 9X, depending on the size of the diaphragm openings. A compound microscope uses more than one lens for magnification. e.g. eyepiece and objective The existence of microscopic organisms was discovered during the period 1665-1683 by two Fellows of the Royal Society of London Robert Hooke (1635–1702) (English philosopher & architect) In Micrographia (1665) Hooke presented the first published depiction of a microorganism, the micro-fungus Mucor Anton van Leeuwenhoek (1632-1723) (Dutch businessman & scientist) (1678) Leeuwenhoek observed and described microscopic protozoa and bacteria. 16 Leeuwenhoek, despite having no scientific training, became the first to observe protozoa, red blood cells, the sperm cells of animals, and bacteria, which he described in numerous letters to the Royal Society of London After a period of more than 150 years, microscopy became the backbone of our understanding of the roles of microbes in the causation of infectious diseases and the recycling of chemical elements in the biosphere. Microscopes Light Microscopes (dissecting and compound) Bright field and Dark field microscopes Differential interference contrast (DIC) microscopy, also known as Nomarski interference contrast (NIC). Optical technique used to enhance the contrast in unstained, transparent samples. Fluorescence microscopes Confocal microscopes (laser) Transmission electron microscopes Scanning electron Microscopes Microscopes & Microscopy Compound light microscope Transmission electron microscope (Tomography) Laser scanning confocal microscope Light Microscope SEM Confocal Electron Microscopy SEM (scanning) Scans the surface of the object TEM (transmission) Transmits electrons through an ultrathin section to show internal ultrastructural features, such as a nucleus Kudoa islandica : species of myxosporean infecting the trunk muscles of three Icelandic fish Int J Parasitol Parasites Wildl. 2014 Jun 21;3(2):135-46. TEM: Transmission Electron Microscopy TEM is a microscopy technique in which a beam of electrons is transmitted through an ultra-thin specimen Embedding blocks/ Beem capsules, using a hard plastic resin TEM: Transmission Electron Microscopy (cellular ultrastructure) Microtome for cutting ultrathin sections 80nm SEM: Scanning Electron Microscopy SEM is a type of electron microscopy that produces images of a sample by scanning it with a focused beam of electrons, to reveal information about the sample's surface topography. Specimens are usually whole and not cut into sections, and are sputter coated with an inert metal, such as gold before scanning can be done 27 Spontaneous Generation Debate The belief in the spontaneous generation of life from non-living matter was introduced by Aristotle, (384-322 BCE), a Greek philosopher. Observations Aphids arose from the dew which falls on plants, Fleas came from putrid matter, Mice from dirty hay “These beliefs remained largely unchallenged for more than 2000 years” Spontaneous Generation Spontaneous Generation: Francesco Redi (1626–1697) Italian physician, biologist and poet! Francesco Redi disproved spontaneous generation (for large organisms) by showing that maggots arose from meat only when flies laid eggs in the meat. Needham: English biologist and Roman Catholic Priest Spallanzani: Italian Catholic priest, biologist and physiologist Lazzaro Spallanzani (1729-1799) Conclusion: Microbes come from the air and boiling will kill them Spontaneous Generation; Louis Pasteur Disproved the theory of spontaneous generation using swan-neck flasks Complex living things only come from other living things, by means of reproduction. Therefore, modern life does not arise from non-living material. Louis Pasteur (1822-1895) French biologist, microbiologist and chemist Often regarded as “The Father of Microbiology” Notable Contributions in Microbiology 1857 – Lactic acid fermentation is due to a microorganism 1860 – Yeasts are involved in alcoholic fermentation 1861 – Disproved the theory of spontaneous generation 1861 – sugar fermentation- The Pasteur Effect 1862 – Proposed germ theory of disease 1867 – process of destroying bacteria known as pasteurization 1881 – Development of anthrax vaccine and resolved pebrine problem of silkworms (microsporidian Nosema) 1885 – Development of a special vaccine for rabies (the Pasteur treatment) The germ theory of disease states that many diseases are caused by microorganisms. These small organisms, too small to see without magnification, invade humans, animals, and other living hosts. Their growth and reproduction within their hosts can cause a disease. Avirulent (attenuated) strains to prevent diseases Louis Pasteur & Charles Chamberland Inoculation of an attenuated chicken cholera bacteria, does not cause disease This is the conceptual breakthrough for establishing protection against disease by the inoculation of a weakened strain of the causative agent Chamberland accidentally ‘discovered’ this breakthrough. He left a culture growing over a short vacation (but had been told by Pasteur to inject/infect the chickens BEFORE the vacation). When he returned, realizing his mistake, he injected the chickens anyway; but the chickens did not get sick or die! Admitting his mistake, Pasteur directed him to inject fresh cultures into the chickens; and they still did not get sick! Louis Pasteur, Rabies vaccine and Joseph Meister 1885 Joseph Meister was the first person to be inoculated against rabies by Louis Pasteur, and the first person to be successfully treated for the infection. In 1885, nineyear-old Meister was badly bitten by a rabid dog. The vaccine consisted of a sample of the virus harvested from infected/rabid rabbits, which was weakened by allowing it to dry for 5 to 10 days. Robert Koch (18431910) German physician, microbiologist Founder of modern microbiology Tuberculosis As a result of his groundbreaking research on tuberculosis, Koch received the Nobel Prize in Anthrax Physiology or Medicine in 1905 Koch’s work with anthrax is notable in that he was the Cholera first to link a specific microorganism with a specific disease, rejecting the idea of spontaneous generation and supporting the germ theory of disease Koch’s Original Postulates Four criteria that were established to identify the causative agent of a particular disease The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. The microorganism must be isolated from a diseased organism and grown in pure culture The cultured microorganism should cause disease when introduced into a healthy organism. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent. Koch’s Original Postulates Did Koch’s Postulate work for Robert Koch? Valid today? Koch’s Postulates: Four criteria that were established to identify the causative agent of a particular disease The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. The microorganism must be isolated from a diseased organism 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. Through his experiments with TB in guinea pigs he found that his experiments with tuberculosis satisfied all four of his postulates However, he abandoned the universal requirement of the first postulate altogether when he discovered asymptomatic carriers of cholera and typhoid The third postulate specifies "should“ and not "must" because as Koch himself proved in regard to both tuberculosis and cholera, not all organisms exposed to an infectious agent will acquire the infection. Non-infection may be due to such factors as general health and proper immune functioning; acquired immunity from previous exposure or vaccination; or genetic immunity The second postulate may also be suspended for certain microorganisms or entities that cannot (at the present time) be grown in pure culture, such as prions In summary, a body of evidence that satisfies Koch's postulates is sufficient but not necessary to establish causation Lecture-2 Microbiology: History Microbial classification nomenclature and Identification Joseph Lister (1827- 1912) Developed a system of antiseptic surgery designed to prevent microorganisms from entering wounds (1867) Father of antiseptic surgery- Sterile Surgery using Carbolic Acid (Phenol) Aromatic organic compound with the molecular formula C6 H5 OH (phenol ring) British surgeon: he noticed that carbolic acid had a remarkable effect on sewage, as it killed ‘entozoans’ (endoparasites) which affected cattle feeding on contaminated pasture Surgery: He was aware that surgeons never washed their hands. They took pride in their dirty blood-stained clothes and unwashed gowns as a display of their surgical experience. Introduced clean gowns and insisted on hand-washing!! Lister also studied the lactic acid fermentation of milk and demonstrated the specific cause of milk souring (1878) He developed a method for isolating a pure culture of a bacterium, named as Bacterium lactis (synonym of Lactococcus lactis) Edward Jenner 1749-1823 ‘Father of Immunology’ Edward Jenner, English physician 1798 - Edward Jenner’s use of cowpox as a vaccine against smallpox “a less pathogenic agent could confer protection against a more pathogenic one” (Louis Pasteur; Started the modern era of vaccines and vaccination in 1880’s) Lady Mary Wortley Montagu (15 May 1689 – 21 August 1762) ‘Variolation’ used live smallpox virus in the liquid taken from a smallpox blister in a mild case of the disease. Variolation or inoculation was the method first used to immunize an individual against smallpox (Variola) with material taken from a patient or a recently variolated individual in the hope that a mild, but protective infection would result. Known: Smallpox is more dangerous than variolation and cowpox less dangerous than variolation Hypothesis: Infection with cowpox gives immunity to smallpox. Test: If variolation after infection with cowpox fails to produce a smallpox infection, immunity to smallpox has been achieved Rudolf Virchow (1821-1902) German Physician and Pathologist Public health activist, started to look at diseases in a different way Cell Theory; “every cell stems from another cell” Cellular Pathology Virchow noted the link between diseases of humans and animals and coined the term “zoonosis” He is often referred to as ‘the father of modern pathology’ as his work involved introducing more science to medicine. He is also known as the founder of social medicine and veterinary pathology! Alexander Fleming (1881-1955) Alexander Fleming, a Scottish biologist, pharmacologist and botanist Alexander Fleming, (1922) discovered that lysozyme, an enzyme found in tears, saliva and sweat, could kill bacteria, the first body secretion shown to have chemotherapeutic properties. He also discovered the first antibiotic, Penicillin in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Florey and Ernst Boris Chain Ferdinand J. Cohn (1828-1898) German biologist classified algae as plants (is that correct?) His classification of bacteria into four groups based on shape (spherical, short rods, threads, and spirals) is still in use today First to show that Bacillus can change from a vegetative state to an endospore state when subjected to an environment deleterious to the vegetative state. Édouard Chatton (1883-1947) (1937) French biologist who first characterized the distinction between the eukaryotic and prokaryotic systems of cellular organization based on presence or absence of nucleus Prokaryotes (before nucleus)--no true nucleus Eukaryotes- Have a nucleus Elie Metchnikoff (1845-1916): ‘father of natural immunity’ Ilya Metchnikoff was a Russian (Marine) biologist Described “phagocytosis” = the eating of cells”. A defensive process in which the body’s white blood cells engulf and destroy microorganisms. The body is protected from infection by leukocytes that engulf bacteria and other invading organism; cellular immunity. https://www.ncbi.nlm.nih.gov/pubmed/19039772 Giovanni Battista Grassi (1854-1924) Italian physician and zoologist, best known for his work on parasite life cycles, including nematodes and malaria David Bruce (1855-1931) Flagellated protozoans He investigated ‘Malta fever’ (brucellosis) and trypanosomes, identifying the cause of sleeping sickness. The kinetoplastid (Excavata) protist/protozoan we now call Trypanosoma brucei He also described Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by the protozoan Trypanosoma cruzi also spread by insects Viruses Dmitri Ivanowsky (1892) discovered viruses Filterability of an infectious agent which caused tobacco mosaic disease Martinus Beijerinck In 1898, he published results on the filtration experiments demonstrating that tobacco mosaic disease is caused by an infectious agent smaller than a bacterium Édouard Chatton