Lecture 1: History and Scope of Microbiology PDF

The History and Scope of Microbiology Lecture : 1 Bio 202 / Mic 101 Professor Dr. S. M. Mostafa Kamal Khan Department of Biochemistry & Microbiology  Microbes in our lives By accident or choice, humans have been using microorganis...

The History and Scope of Microbiology Lecture : 1 Bio 202 / Mic 101 Professor Dr. S. M. Mostafa Kamal Khan Department of Biochemistry & Microbiology  Microbes in our lives By accident or choice, humans have been using microorganisms for thousands of years to improve life and even to shape civilizations. Harmful roles of Microorganisms:  Major diseases such as AIDS, Infections  Food spoilage Beneficial roles of Microorganisms:  Maintain the balance of living organisms and chemicals in our environment.  Marine and freshwater microorganisms form the basis of the food chain in oceans, lakes, and rivers.  Soil microbes help break down wastes and incorporate nitrogen gas from the air into organic compounds  Recycle chemical elements between the soil, water, life and air.  Certain microbes play important roles in photosynthesis, that is critical to life on Earth.  Humans and many other animals depend on the microbes in their intestines for digestion and the synthesis of some vitamins that their bodies require  Commercial Applications of Microbes They are used in the synthesis of such chemical products as  Vitamins,  Organic acids,  Enzymes,  Alcohols, and  Many drugs. Microbes in Food Industry Green olives Vinegar Buttermilk Alcoholic Beverages Pickles Sauerkraut  Microbial enzymes helps to produce jeans  The Science Microbiology ‘Microbiology’ should be an easy word to define: The science (logos) of small (micro) life (bios), or to put it another way, “The study of living things so small that they cannot be seen with the naked eye- that is, the study of microorganisms”. The science of microbiology revolves around two interconnected themes: 1. Understanding the living world of microscopic organisms, and 2. Applying our understanding of microbial life processes for the benefit of humankind and planet Earth.  Objects less than about one millimetre (1 mm) in diameter cannot be seen clearly and must be examined with a microscope, microbiology is concerned primarily with organisms and agents this small and smaller. Microbial habitats a) Summer pond with a thick mat of algae- a rich photosynthetic community b) Microbes play a large role in decomposing dead animal and plant matter The Pink Lake Hiller lake in Western Australia - Scientists have proven the strange pink color is due to the presence of algae which is usually the cause of strange coloration. The most notable feature of the lake is its pink, vibrant colour. The vibrant colour is permanent, and does not alter when the water is taken in a container. 10 species of salt- loving bacteria and several species of Dunaliella algae. The pink colour is considered to be due to the presence of the organism Dunaliella salina A popular hypotheses about the origins of the Red Sea's name is that it contains a cyanobacteria called Trichodesmium erythraeum, which turns the normally blue- green water a reddish-brown.  Microbial communities Scanning electron micrograph of a microbial community scraped from a human tongue.  Microbes and Human Welfare Biotechnology: When humans manipulate microorganisms to make products in an industrial setting, it is called biotechnology. For example, some specialized bacteria have unique capacities to mine precious metals or to clean up human-created contamination. Genetic engineering: an area of biotechnology that manipulates the genetics of microbes, plants, and animals for the purpose of creating new products and genetically modified organisms (GMOs). Recombinant DNA technology: technology makes it possible to transfer genetic material from one organism to another and to deliberately alter DNA. Bacteria and fungi were some of the first organisms to be genetically engineered.  Microorganisms as Agents of Disease Particularly in developing countries microbial diseases are still the major causes of death, and millions still die yearly from other microbial diseases such as malaria, tuberculosis, cholera, African sleeping sickness, measles, pneumonia and other respiratory diseases, and diarrheal syndromes. In addition to these, humans worldwide are under threat from diseases that could emerge suddenly, such as bird or swine flu, or Ebola hemorrhagic fever, which are primarily animal diseases that under certain circumstances can be transmitted to humans and spread quickly through a population.  Microbes In Agriculture and Human Nutrition Agriculture benefits from the cycling of nutrients by microorganisms. A number of major crop plants that feed humans and domesticated animals are legumes. Legumes live in close association with bacteria that form structures called nodules on their roots. In the nodules, these bacteria convert atmospheric nitrogen (N2) into ammonia (NH3), which is called nitrogen fixation. Plants use it as a nitrogen source for growth. Nitrogen fixation also eliminates the need for farmers to apply costly and polluting nitrogen fertilizers. Bacterial sulfur cycle, oxidizing toxic sulfur compounds such as hydrogen sulfide (H2S) into sulfate (SO42-), which is nontoxic and an essential plant nutrient. Major agricultural importance are microorganisms that inhabit the rumen of ruminant animals like cattle and sheep. The rumen is a microbial ecosystem in which large populations of microorganisms digest and ferment the polysaccharide cellulose, the major component of plant cell walls (Figure 1b,d). Without these symbiotic microorganisms, ruminants could not thrive on cellulose rich (but otherwise nutrient-poor) food, such as grass and hay. Microbes In Agriculture and Human Nutrition Figure: Microorganisms in modern agriculture. (a, b) Root nodules on this soybean plant contain bacteria that fix molecular nitrogen (N2) for use by the plant. (c) The nitrogen and sulfur cycles, key nutrient cycles in nature. (d) Ruminant animals. Microorganisms in the rumen of the cow convert cellulose from grass into fatty acids that can be used by the animal. The other products are not so desirable, as CO2 and CH4 are the major gases that cause global warming.  Microorganisms in Human GI tract The human gastrointestinal (GI) tract lacks a rumen, and microbial numbers comparable to those in the rumen (about 1011 microbial cells per gram of contents) occur only in the colon (large intestine). Microorganisms in the colon assist in digestive processes by synthesizing certain vitamins and other essential nutrients but also compete for space and resources with pathogenic microorganisms that may enter the GI tract in contaminated food and water. Thus by their sheer numbers alone, the colonic microflora help prevent pathogens from gaining a foothold. A. The human gastrointestinal tract. B. Human tongue (A) The human gastrointestinal tract. (a) Diagram of the human GI tract showing the major organs. (b) Scanning electron micrograph of microbial cells in the (B) Scanning electron micrograph of a microbial community scraped human colon (large intestine). Cell numbers in the colon can reach as high as from a human tongue. 1011 per gram. As well as cell numbers, the microbial diversity in the colon is also quite high.  Microbes in food processing Many dairy products depend on the activities of microorganisms to produce key acids characteristic of the products, such as in the fermentations that yield cheeses, yogurt, and buttermilk. Sauerkraut, pickles, and some sausages are also subject to microbial fermentations. Baked goods and alcoholic beverages rely on the fermentative activities of yeast, which generate carbon dioxide (CO2) to raise the dough and alcohol as a key ingredient, respectively. These products of fermentation are not only desirable chemicals but also function to preserve the food product from deleterious microbial growth.  Microbes in food processing Fermented foods. (a) Major fermentations in various fermented foods. It is the fermentation product (ethanol, or lactic, propionic, or acetic acids) that both preserves the food and renders in it a characteristic flavor. (b) Photo of several fermented foods showing the characteristic fermentation product in each.  Microbes in energy production Some microorganisms produce biofuels. For example, natural gas (methane, CH4) is a product of the anaerobic metabolism of a group of Archaea called methanogens. Ethyl alcohol (ethanol), which is produced by the microbial fermentation of glucose obtained from feedstocks such as sugarcane, corn, or rapidly growing grasses, is a major motor fuel or fuel supplement (Figure 4). Waste materials such as domestic refuse, animal wastes, and cellulose can also be converted to ethanol and methane; and soybeans contain oils that can be converted into fuel for diesel engines. Microbes in energy production Ethanol as a biofuel. (a) Major crop plants used as feedstocks for biofuel ethanol production. Top: switchgrass, a source of cellulose. Bottom: corn, a source of cornstarch. Both cellulose and starch are composed of glucose, which is fermented to ethanol by yeast. (b) An ethanol plant in the United States. Ethanol produced by fermentation is distilled and then stored in the tanks.  Microbiology in Historical context Theory of Spontaneous Generation This theory assumed that living organisms could arise suddenly and spontaneously from any kind of non-living matter. One of the firm believers in spontaneous generation was Aristotle, the Greek philosopher (384-322 BC) – The Father of Zoology. The theory of Spontaneous Generation was disproved in the course of time due to the experiment conducted by Fransisco Redi, (1665), Spallanzani (1765) and later by Louis Pasteur (1864) in his famous “S-neck” experiment. This theory was disapproved, as scientists gave definite proof that life comes from pre-existing life. The Development of Microscope Because of Leeuwenhoek’s extraordinary contributions to microbiology, he is known as the Father of Bacteriology and Protozoology. Figure: Antony van Leeuwenhoek. Leeuwenhoek (1632–1723) and his microscopes. (a) Leeuwenhoek holding a microscope. (b) A drawing of one of the microscopes showing the lens, a; mounting pin, b; and focusing screws, c and d. (c) Leeuwenhoek’s drawings of bacteria from the human mouth.  Louis Pasteur (1861) Arguments about spontaneous generation continued until 1861, when the issue was resolved by the French scientist Louis Pasteur. With a series of ingenious and persuasive experiments, Pasteur demonstrated that microorganisms are present in the air and can contaminate sterile solutions, but that air Figure 4 Louis Pasteur (1822–1895), one of the founders of microbiology. Few microbiologists itself does not create microbes. can match the scope and impact of his contributions to the science of microbiology. Figure: The defeat of spontaneous generation: Pasteur’s swan-necked flask experiment. In (c) the liquid putrefies because microorganisms enter with the dust. The bend in the flask allowed air to enter (a key objection of Pasteur’s sealed flasks) but prevented microorganisms from entering.  Fermentation and Pasteurization Pasteur found that microorganisms called yeasts convert the sugars to alcohol in the absence of air. This process, called fermentation, is used to make wine and beer. Souring and spoilage are caused by different microorganisms called bacteria. In the presence of air, bacteria change the alcohol in the beverage into vinegar (acetic acid). Pasteur's solution to the spoilage problem was to heat the beer and wine just enough to kill most of the bacteria that caused the spoilage. The process, called pasteurization, is now commonly used to reduce spoilage and kill potentially harmful bacteria in milk as well as in some alcoholic drinks.  The Germ Theory of Disease Robert Koch in 1876 a German physician, was Pasteur's young rival in the race to discover the cause of anthrax, a disease that was destroying cattle and sheep in Europe. Koch discovered rod- shaped bacteria now known as Bacillus anthracis in the blood of cattle that had died of anthrax. He cultured the bacteria on nutrients and then injected samples of the culture into healthy animals. When these animals became sick and died, Koch isolated the bacteria from their blood and compared them with the bacteria originally Figure: Robert Koch. The German isolated. He found that the two sets of blood physician and microbiologist is credited with founding medical microbiology and cultures contained the same bacteria. formulating his famous postulates. Figure: Koch’s postulates for proving cause and effect in infectious diseases. Note that following isolation of a pure culture of the suspected pathogen, the cultured organism must both initiate the disease and be recovered from the diseased animal. Establishing the correct conditions for growing the pathogen is essential; otherwise it will be missed. Reference Book: Brock Biology of Microorganisms (14th Edition) Microorganisms and Their Environments; Pg. 6 The Impact of Microorganisms on Humans; Pg. 8 The Discovery of Microorganisms; Pg. 13 Pasteur and Spontaneous Generation; Pg. 13 Koch, Infectious Disease, and Pure Cultures; Pg. 16