Introductory Microbiology Lecture 1 PDF

BIOL/MCBL 121 INTRODUCTORY MICROBIOLOGY Lecture 1 General Course Information Introduction and History of Microbiology Copyright Ansel Hsiao 2021 Objectives • Introduce diversity of microorganisms and impact of microbes on humans • Be able to describe the theory of spontaneous generation and how...

BIOL/MCBL 121 INTRODUCTORY MICROBIOLOGY Lecture 1 General Course Information Introduction and History of Microbiology Copyright Ansel Hsiao 2021 Objectives • Introduce diversity of microorganisms and impact of microbes on humans • Be able to describe the theory of spontaneous generation and how it was disproved • Understand how Koch’s Postulates are used to describe the role of microbes in diseases (Germ Theory) Copyright Ansel Hsiao 2021 Microorganisms • Any living organisms too small to be seen with the naked eye Bacteria Archaea Prokaryotes Algae Fungi Protist Copyright Ansel Hsiao 2021 Eukaryotes Viruses Microorganisms • Everything has exceptions • Supersize microbial cells • Example: Thiomargarita namibiensis • Microbial communities • Example: biofilms • Viruses • Example: mimivirus (several hundred micron) Copyright Ansel Hsiao 2021 Microorganisms Microorganisms are some of the most metabolically and genetically diverse organisms on the planet. Copyright Ansel Hsiao 2021 Microbes Shape Human History • Microbes affect food availability • Can destroy crops, but preserve food • Alcohols, cheese, chocolate • Irish Potato Famine (eukaryotic microbe) Copyright Ansel Hsiao 2021 Microbes Shape Human History • Microbes affect food availability • Can destroy crops, but preserve food • Alcohols, cheese, chocolate • Irish Potato Famine (eukaryotic microbe) • Microbes are a part of us: • Humans, animals, and plants are colonized with microbes Copyright Ansel Hsiao 2021 Microbes Shape Human History • Microbes affect food availability • Can destroy crops, but preserve food • Alcohols, cheese, chocolate • Irish Potato Famine (eukaryotic microbe) • Microbes are a part of us: • Humans, animals, and plants are colonized with microbes • Microbial diseases change history • Smallpox in Americas • Bubonic plague Copyright Ansel Hsiao 2021 Bacterial diseases: plague • Black Death (peaked 1348-1350 Europe) • Caused by bacterium Yersinia pestis • Spread via fleas carried on rats • Originated in China, killed one-third to one-half of Europe’s population during the epidemic of 1346-1353 Copyright Ansel Hsiao 2021 Discovery of Microbes • Observation • Etiology - the study of causes • How are microbes generated? • How do we assign roles to microbes? Copyright Ansel Hsiao 2021 Robert Hooke (1635-1703) • Invented compound microscope • Described the first microbes • Fruiting structures of fungi Copyright Ansel Hsiao 2021 Antonie van Leeuwenhoek (1632-1723) • Dutch amateur lens grinder • First observed single-celled organisms “animacules” – bacteria Copyright Ansel Hsiao 2021 Where do microbes come from? • We know now that bacteria, archaea, microscopic eukaryotes are cells, and a lot about how those cells are organized and function • Early microbiologists had many ideas about where these small organisms came from • “Spontaneous generation” is the theory that living creatures could arise without parents (started with Aristotle) – disproving this idea was a long process Copyright Ansel Hsiao 2021 Where do microbes come from? • Francesco Redi (1660s) - Did perhaps the first real biological experiment: Observation: There are flies around meat carcasses at the butcher shop. Question: Where do the flies come from? Does rotting meat turn into or produce the flies? Hypothesis: Rotten meat does not turn into flies. Only flies can make more flies. Prediction: If meat cannot turn into flies, rotting meat in a sealed (fly-proof) container should not produce flies or maggots. Copyright Ansel Hsiao 2021 Where do microbes come from? • Testing: Wide-mouth jars each containing a piece of meat were left open to various degrees Control Group Copyright AnselExperimental Hsiao 2021 Groups Where do microbes come from? • Conclusion(s): Only flies can make more flies. • Flies laid eggs directly on exposed meat, which turned into maggots and then into flies • No eggs or flies observed at all on meat in sealed jars • Flies laying eggs on gauze that dropped onto meat • Maggots arose only when flies were able to lay eggs • This experiment disproved the idea of spontaneous generation for larger organisms. Copyright Ansel Hsiao 2021 Where do microbes come from? • A theory in the 1700s was that there was a “life force” present in matter, including air and oxygen. • Meat broth exposed to the air grew bacteria • Lazzaro Spallanzani (1760s) • Showed that a sealed flask of meat broth sterilized by boiling for long periods failed to grow microbes (i.e., spoil) • Spallanzani’s sterilization experiments was attacked because it did not allow access to air Copyright Ansel Hsiao 2021 Louis Pasteur (1822-1895) • Food Microbiology: • Fermentation • Pasteurization and Sterilization • Connected the cause (microorganisms) and the effect (metabolic products) • Disproved “spontaneous generation” via the Swan-necked flask experiment • Combined sterilization via boiling with access to air and whatever “life force” was in it Copyright Ansel Hsiao 2021 Swan-necked flask experiment Copyright Ansel Hsiao 2021 Oxygen alone does not enable spontaneous generation of microorganisms Copyright Ansel Hsiao 2021 Liquid remained sterile until microorganisms were introduced from outside Copyright Ansel Hsiao 2021 Robert Koch (1843-1910) • Pasteur’s work suggested that microbes could be the source of disease • Working with anthrax, Koch demonstrated an important principle of epidemiology: the chain of infection, or transmission of a disease • Koch proved Germ Theory of Disease • A specific type of microorganism causes a specific disease • Methods and principles led to the isolation of pure bacterial cultures Copyright Ansel Hsiao 2021 Growth of microbes in pure culture • To prove a particular bacterium caused a specific disease, pure culture of microorganisms were needed • In broth, all bacteria are mixed Copyright Ansel Hsiao 2021 Growth of microbes in pure culture • Angelina and Walther Hesse • Solid medium using agar • Julius Petri • Double-dish container • Growth on solid medium allowed the isolation of clonal (pure) cultures of bacteria Copyright Ansel Hsiao 2021 Growth of microbes in pure culture • Each colony or spot of bacterial growth represents the progeny of one original cell • Colonies are clonal – replicates of the original cell that started the colony • Isolating colonies of bacteria and growth in broth allowed for isolation of clonal populations of bacteria in pure culture (one kind of bacteria) Copyright Ansel Hsiao 2021 Koch’s Postulate Number 1 Postulate 1 – The suspected organism should be present in ALL cases of the disease and ABSENT from healthy animals Copyright Ansel Hsiao 2021 Koch’s Postulate Number 2 Postulate 2 – The suspected organism should be grown in PURE CULTURE Copyright Ansel Hsiao 2021 Koch’s Postulate Number 3 Postulate 3 – Cells from a pure culture of the suspected organism should CAUSE DISEASE in a healthy animal Copyright Ansel Hsiao 2021 Koch’s Postulate Number 4 Postulate 4 – The suspected organism should be REISOLATED (the same organism as before) Copyright Ansel Hsiao 2021 Koch’s Postulates: Limitations • Slow-growing pathogens or pathogens may fail postulates • Pathogens may not be culturable with known techniques • The original host (e.g. human) is not always available for inoculation Copyright Ansel Hsiao 2021 Koch’s Postulates: Alternatives • Animal models in place of humans for studying the causal role of bacterial pathogens in diseases • Correlative studies associating particular bacteria or bacterial communities with a disease through molecular biology or immunology approaches • Eliminating the disease-causing microbe from the infected host or prevention of exposure of the host to the microbe should eliminate or prevent disease Copyright Ansel Hsiao 2021