The History and Scope of Microbiology PDF

The History and Scope of Microbiology Introduction to Microbiology  Microbiology is the study of microorganisms usually less than 1mm in diameter which requires some form of magnification to be seen clearly ⚫ Examples:  Viruses  Bacteria...

The History and Scope of Microbiology Introduction to Microbiology  Microbiology is the study of microorganisms usually less than 1mm in diameter which requires some form of magnification to be seen clearly ⚫ Examples:  Viruses  Bacteria  Fungi  Algae  Protozoans  Some organisms studied by microbiologists CAN be visualized without the aid of amplification [bread molds (fungus) and filamentous algae] ⚫ These organisms are included in the discipline of microbiology because of similarities in properties and techniques used to study them  Techniques necessary to isolate and culture microorganisms ⚫ Isolation ⚫ Sterilization ⚫ Culture in artificial media  Microbiologists may be interested in specific types of organisms: ⚫ Virologists - viruses ⚫ Bacteriologists - bacteria ⚫ Phycologists or Algologists - algae ⚫ Mycologists - fungi ⚫ Protozoologists - protozoa  Microbiologists may have a more applied focus: ⚫ Medical microbiology, including immunology ⚫ Food and dairy microbiology ⚫ Public health microbiology ⚫ Industrial microbiology ⚫ Agricultural microbiology  Microbiologists may be interested in various characteristics or activities of microorganisms: ⚫ Microbial morphology ⚫ Microbial cytology ⚫ Microbial physiology ⚫ Microbial ecology ⚫ Microbial genetics and molecular biology ⚫ Microbial taxonomy  Historical Perspectives  Early Discoveries  Lucretius, a Roman philosopher (98-55 B.C.), and Girolamo Fracastoro, a physician (1478- 1553) believed invisible creatures were responsible for disease  Franscesco Stelluti observed bees and weevils using a microscope in the early 1600s  Anton van Leeuwenhoek (1632 - 1723) was the first to report microorganisms (Royal Society) (Animalcules) ⚫ 50-300X magnification Spontaneous Generation  Spontaneous Generation ⚫ The belief that life could originate from non-living or decomposing matter  Supported by: ⚫ Aristotle (384-322 BC) – Believed that simple invertebrates could arise by spontaneous generation ⚫ John Needham (1713-1781) – Boiled mutton broth, then sealed and still observed growth after a period of time ⚫ Lazarro Spallanzani (1729-1799) No growth in sealed flask after boiling – proposed that air was needed for growth of organisms ⚫ Felix Pouchet (1859) – Proved growth without contamination from air  Disproved by: ⚫ Francesco Redi (1626-1697) – maggot unable to grow on meat if meat was covered with gauze ⚫ Schwann, Friedrich Schroder and von Dusch (1830s) – Air allowed to enter flask but only after passing through a heated tube or sterile wool ⚫ John Tyndall (1820-1893) – Omission of dust → no growth. Demonstrated heat resistant forms of bacteria (endospores) ⚫ Louis Pasteur (1822 - 1895)  trapped airborne organisms in cotton;  he also heated the necks of flasks, drawing them out into long curves, sterilized the media, and left the flasks open to the air;  no growth was observed because dust particles carrying organisms did not reach the medium, instead they were trapped in the neck of the flask; if the necks were broken, dust would settle and the organisms would grow; in this way Pasteur disproved the theory of spontaneous generation  Role of Micoorganisms in Disease  Demonstrations that microorganisms cause disease  Agostino Bassi (1773 - 1856) ⚫ showed that a silkworm disease was caused by a fungus  M. J. Berkeley (ca. 1845) ⚫ demonstrated that the Great Potato Blight of Ireland was caused by a Fungus  Louis Pasteur ⚫ showed that the pébrine disease of silkworms was caused by a protozoan parasite  Joseph Lister (1827 - 1912) ⚫ developed a system of surgery designed to prevent microorganisms from entering wounds – phenol sprayed in air around surgical incision ⚫ Decreased number of post-operative infections in patients ⚫ his published findings (1867) transformed the practice of surgery  Charles Chamberland (1851 - 1908) ⚫ identified viruses as disease-causing agents – Tobacco Mosaic Virus  Edward Jenner (ca. 1798) ⚫ used a vaccination procedure to protect individuals from smallpox  Louis Pasteur ⚫ developed other vaccines including those for chicken cholera, anthrax, and rabies  Ignaz Semmelweiss (~1850) demonstrated that childbed fever (puerperal fever), caused by streptococcal infections, was transmitted to patients by doctor’s hands ⚫ Pioneer of antisepsis in obstetrics ⚫ Women giving birth in hospitals by medical students and physicians were 4x more likely to contract puerperal fever compared to those by midwives  Emil von Behring (1854 - 1917) and Shibasaburo Kitasato (1852 - 1931) ⚫ induced the formation of diphtheria tetanus antitoxins in rabbits which were effectively used to treat humans thus demonstrating humoral immunity  Elie Metchnikoff (1845 - 1916) ⚫ demonstrated the existence of phagocytic cells in the blood, thus demonstrating cell- mediated immunity  Robert Koch (1843 - 1910), ⚫ using criteria developed by his teacher, Jacob Henle (1809-1895), established the relationship between Bacillus anthracis and anthrax; ⚫ his criteria became known as Koch’s Postulates and are still used to establish the link between a particular microorganism and a particular disease: Koch’s Postulates  The causative (etiological) agent must be present in all affected organisms but absent in healthy individuals  The agent must be capable of being isolated and cultured in pure form  When the cultured agent is introduced to a healthy organism, the same disease must occur  The same causative agent must be isolated again from the affected host Development of Culture Media  Why? ⚫ To enable the isolation of pure cultures (only one type of organism)  Especially important during Koch’s period  Gelatin not useful as solidifying agent (melts at >28 degrees Celsius and some bacteria hydrolyze it with enzymes)  Fannie Hesse, the wife of one of Koch’s assistants, proposed using agar ⚫ Not digested by most bacteria ⚫ Melts at 100 degrees Celsius ⚫ Used today - ~2% in solid media  Richard Petri, another of Koch’s assistants, developed the Petri dish  Development of Vaccines and Antisera  Edward Jenner in 1796 discovered that cowpox (vaccinia) induced protection against human smallpox ⚫ Called procedure vaccination  Vaccination: ⚫ Inoculation of healthy individuals with weakened (or attenuated) forms of microorganisms, that would otherwise cause disease, to provide protection, or active immunity from disease upon later exposure  Pasteur and Roux reported that incubating cultures longer than normal in the lab resulted in ATTENUATED bacteria that could no longer cause disease ⚫ Working with chicken cholera (caused by Pasteurella multocida), they noticed that animals injected with attenuated cultures were resistant to the disease  Pasteur and Chamberland developed other vaccines: ⚫ Attenuated anthrax vaccine  Chemical and heat treatment (potassium bichromate) ⚫ Attenuated rabies vaccine  Propagated the virus in rabbit following injection of infected brain and spinal cord extracts  Passive immunization ⚫ Work by Emil von Behring (1845-1917) and Shibasaburo Kitasato (1852-1931)  Antibodies raised to inactivated diphtheria toxin by injection of different host (rabbit) with the toxin (a toxoid form) ⚫ Antiserum recovered  Contains antibodies specific for the toxin  Protection from disease when injected nonimmune subject How Microorganism Affect Their Environment  Louis Pasteur ⚫ demonstrated that alcoholic fermentations were the result of microbial activity, ⚫ that some organisms could decrease alcohol yield and sour the product, and ⚫ that some fermentations were aerobic and some anaerobic; ⚫ he also developed the process of pasteurization to preserve wine during storage  Sergei Winogradsky (1856 - 1953) ⚫ worked with soil bacteria and discovered that they could oxidize iron, sulfur, and ammonia to obtain energy; ⚫ he also studied anaerobic nitrogen-fixation and cellulose decomposition  Martinus Beijerinck (1851 - 1931) ⚫ isolated aerobic nitrogen-fixing soil bacteria (Azotobacter and Rhizobium) and sulfate reducing Bacteria  Beijerinck and Winogradsky ⚫ pioneered the use of enrichment cultures and selective media Microorganisms in th the 20 Century  Important Early Discoveries  George W. Beadle and Edward L. Tatum (ca. 1941) ⚫ studied the relationship between genes and enzymes using the bread mold, Neurospora ⚫ Precursor→ ornithine → citrulline → arginine ⚫ One gene, one polypeptide hypothesis  Salvadore Luria and Max Delbruck (ca. 1943) ⚫ Demonstrated spontaneous gene mutations in bacteria (not directed by the environment)  Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty (1944) ⚫ Following initial studies by Frederick Griffith (1928) they provided evidence that deoxyribonucleic acid (DNA) was the genetic material and carried genetic information during transformation ⚫ Worked with Streptococcus pneumoniae (rough and smooth) ⚫ Microbiology has played a major role in molecular biology and has been closely tied to the determination of the genetic code;  in studies on the mechanisms of DNA, ribonucleic acid (RNA), and protein synthesis;  and in studies on the regulation of gene expression and the control of enzyme activity ⚫ Microorganisms are able to grow rapidly and in large amounts in the lab at reasonable cost  Valuable research tools for studying genetics, biochemistry, molecular biology and cell biology  In the 1970s new discoveries in microbiology led to the development of recombinant DNA technology and genetic engineering Thank you!