The Discovery of Microorganisms Lecture 1 PDF

The discovery of microorganisms Lecture 1  Importance of Microorganisms Microorganisms existed on earth for billions of years before plants and animals appeared. Microorganisms were the first entities on Earth with the properties of living systems A par tic...

The discovery of microorganisms Lecture 1  Importance of Microorganisms Microorganisms existed on earth for billions of years before plants and animals appeared. Microorganisms were the first entities on Earth with the properties of living systems A par ticular group of microorganisms called the cyanobacteria were pivotal in biological evolution because oxygen (O2)—a waste product of their metabolism that prepared planet Earth for more complex life forms. Cyanobacteria  Importance of Microorganisms In the absence of microorganisms, higher life forms would never have evolved and could not now be sustained. Humans, plants, and animals are intimately tied to microbial activities for the recycling of key nutrients and for degrading organic matter. No other life forms are as important as microbes for the support and maintenance of life on earth. Topics…….  What is microbiology?  Origin of the word microbiology  What is microorganism?  What is microscope?  The beginning of microbiology  Anton van Leeuwenhoek-the father of microbiology  Contribution of the father of microbiology What is microbiology?  Microbiology is the study or science of living organisms of microscopic size that are too small to be clearly seen with naked eyes called microorganisms  Microorganisms exist as single cell or cell clusters  It also include viruses, which are microscopic but not cellular Origin of the word microbiology  “Microbiology” the word derived from three Greek words :  ‘mikros’ meaning small  ‘bios’ meaning life  ‘logos’ meaning science  Meaning together the study of microscopic life What is microorganism?  If an object has a diameter of less than 0.1 mm, the eye cannot perceive it at all  Roughly speaking , organisms with diameter of 1 mm or less are microorganisms  The existence of this microbial world was unknown until the invention of microscopes  Microorganisms have a wide taxonomic distribution What is microorganism?  Microorganisms include metazoan animals, protozoa, many algae and fungi  What is microscope?  Microscope is an optical instrument that serve to magnify objects  Microscope as invented at the beginning of seventeenth century  Zacharias Janssen(1580-1638) was a Dutch spectacle- maker associated with the invention of the first microscope  As a young boy, he combined two lenses to form a crude compound microscope in1590  What is microscope?  The German mathematician and astronomer Johan Kepler(1571-1630), the noted Italian astronomer Galileo(1564-1642) and the English physicist and mathematician Robert Hooke(1635-1703) also worked on the improvements of microscopes What is microscope?  However, it was not until the late 1600s that microscopes became the ultimate choice to observe objects normally not visible to the naked eye  Anton van Leewenhoek(1632-1723) is considered as father of Microbiology  He made hundreds of microscopes in his life time  His microscopes were noted for their lenses(meticulously ground and highly polished) Through the lenses of Microscope…  Robert Hooke experimented extensively with the microscope and illustrated his written observations with detailed drawings of plant tissues  It was Hooke who first described the small cavities separated by walls as ‘‘cells’’ in 1665  “Microglia” is the book in which he described all about his microscopic observation; the book was commissioned by King Charles II of England The beginning of microbiology  The microscopes of Anton van Leewenhoek provided glimpses into an new world consisting of microbes  Leewenhoek called them “animalcules’’ in a letter to the Royal Society of London in 1674  Leewenhoek also described in detail many different types of microbial shapes that we recognize today The beginning of microbiology  Scientist conclude that microorganisms originated around 4 billion years ago from complex organic materials in ocean waters or possibly in vast cloudbanks surrounding our primitive earth  As the first life on earth, microorganisms are thought to be the ancestors of other life forms  Although microorganisms are ancient by any standards, “Microbiology” itself is a comparatively young science The beginning of microbiology  It seems incredible that explorers first observed microorganisms only a little more than 300 years ago and that microorganisms were poorly understood for many years after their discovery  There was a lapse of almost 200 years from the time microbes were first seen to the widespread recognition of their importance Anton van Leeuwenhoek-the father of microbiology  Because of his accomplishment, Anton van Leewenhoek is considered to be the “ Father of Microbiology’’ Van leeuwenhoek using his microscope Anton van Leeuwenhoek-the father of microbiology  He was obviously not the first person to use microscopes to study disease organisms or other extremely small organisms  But Leewenhoek had an insatiable curiosity about the natural world and it is his detailed descriptions of what he saw that make him one of the founders of microbiology Contribution of the father of microbiology  Leewenhoek used his primitive microscopes to observe river water, pepper infusions, saliva, feces and more  He become excited by large number of minute and moving objects, as he thought them tiny little animals  He made more than 250 microscopes which can magnify an object 50 X-300 X  Leewenhoek recorded his observation in a series of letters to the British Royal Society Contribution of the father of microbiology  He describes his little “animals” in great detail, leaving little doubt to the modern reader that he saw bacteria, fungi and many forms of protozoa  In one letter, he first provided the first record drawings of microorganisms now known as bacteria (from scrap of his teeth) Contribution of the father of microbiology  In one letter (September 7, 1674), he described “very little animalcules” now recognized as free living protozoa  Between 1673 and 1723, Leewenhoek described his meticulously recorded observations and sketches in more than 300 letters  This letters altered the world to the existence of microscopic forms of life and gave birth to microbiology Types of Microorganisms Bacteria Bacteria (singular: bacterium) are relatively simple, single-celled unicellular organisms Because their genetic material is not enclosed in a special nuclear membrane, bacterial cells are called prokaryotes from Greek words meaning prenucleus. Prokaryotes include both bacteria and archaea. Bacteria are enclosed in cell walls that are largely composed of a carbohydrate and protein complex called peptidoglycan (By contrast, cellulose is the main substance of plant and algal cell walls.)  Bacteria Bacteria generally reproduce by dividing into two equal cells; this process is called binary fission. For nutrition, most bacteria use organic chemicals, which in nature can be derived from either dead or living organisms. Some bacteria can manufacture their own food by photosynthesis, and some can derive nutrition from inorganic substances. Many bacteria can "swim" by using moving appendages called flagella. Archaea Archaea is derived from the Greek word “archaios”, meaning ancient or primitive Cell walls of archaea lack peptidoglycan Archaea, often found in extreme environments, are divided into three main groups: 1. The methanogens produce methane as a waste product from respiration. 2. The extreme halophile (halo = salt; philic = loving) live in extremely salty environments such as the Great Salt Lake and the Dead Sea. 3. The extreme thermophile (therm = heat) live in hot water, such as hot springs at Yellowstone National Park. Archaea are not known to cause disease in humans.   Archaea were originally discovered and described in extreme environments, such as hydrothermal vents and terrestrial hot springs. They were also found in a diverse range of highly saline, acidic, and anaerobic environments. Hydrothermal vent Yellowstone national park hot spring https://learn.genetics.utah.edu/content/astrobiology/environments/ Fungi Fungi (singular: fungus) are eukaryotes whose cells have a distinct nucleus containing the cell's genetic material (DNA), surrounded by a special envelope called the nuclear membrane. Organisms in the Kingdom Fungi may be unicellular or multicellular. Large multicellular fungi, such as mushrooms, may look somewhat like plants, but they cannot carry out photosynthesis, as most plants can. True fungi have cell walls composed primarily of a substance called Chitin. The unicellular forms of fungi known as yeasts, are oval microorganisms that are larger than bacteria. Fungi The most typical fungi are molds. Molds form visible masses called mycelia. Mycelia are composed of long filaments (hyphae) that branch and intertwine. The cottony growths sometimes found on bread and fruit are mold mycelia. Fungi can reproduce sexually or asexually. They obtain nourishment by absorbing solutions of organic material from their environment- whether soil, seawater, fresh water, or an animal or plant host. Certain organisms are called slime molds because they have characteristics of both fungi and amoebas. Algae Algae (singular: alga) are photosynthetic eukaryotes with a wide variety of shapes Can be unicellular or multicellular The cell walls of many algae, are composed of a carbohydrate called cellulose Algae are abundant in fresh and salt water, in soil, and in association with plants As photosynthesizers, algae need light, water, and carbon dioxide for food production and growth, but they do not generally require organic compounds from the environment. As a result of photosynthesis, algae produce oxygen and carbohydrates that are then utilized by other organisms, including animals. Thus, they play an important role in the balance of nature. Protozoa Protozoa (singular: protozoan) are unicellular eukaryotic microbes. Protozoa move by pseudopods, flagella, or cilia. Amoebas move by using extensions of their cytoplasm called pseudopods (false feet). Other protozoa have long flagella or numerous shorter appendages for locomotion called cilia. Protozoa have a variety of shapes and live either as free entities or as parasites (organisms that derive nutrients from living hosts) that absorb or ingest organic compounds from their environment. Protozoa can reproduce sexually or asexually. Viruses Viruses are very different from the other microbial groups They are so small that most can be seen only with an electron microscope, and they are acellular (not cellular) Structurally very simple, a virus particle contains a core made of only one type of nucleic acid, either DNA or RNA. This core is surrounded by a protein coat. Sometimes the coat is encased by an additional layer, a lipid membrane called an envelope  Viruses Viruses can reproduce only by using the cellular machinery of other organisms. Thus, viruses are considered to be living when they multiply within host cells they infect. On the other hand, viruses are not considered to be living because outside living hosts, they are inert.  HIV Bacteriophage  Theory of Spontaneous Generation/Abiogenesis Life can arise from non-living matter  Spontaneous Generations: Until the second half of the nineteenth century, many scientists and philosophers believed that some forms of life could arise spontaneously from nonliving matter; the process was named spontaneous generation.  People commonly believed that toads, snakes, and mice could be born of moist soil; that flies could emerge from manure; and that maggots, the larvae of flies, could arise from decaying corpses. Opponents of Spontaneous Generation  Experiment of Francesco Redi: A strong opponent of spontaneous generation, the Italian physician Francesco Redi demonstrated that maggots did not arise spontaneously from decaying meat.  Redi filled two jars with decaying meat.  The first was left unsealed; the flies laid their eggs on the meat, and the eggs developed into larvae.  The second jar was sealed, and because the flies could not lay their eggs on the meat, no maggots appeared.  But, Redi's antagonists were not convinced; they claimed that fresh air was needed for spontaneous generation.  Opponents of Spontaneous Generation  So Redi set up a second experiment, in which he covered a jar with fine net instead of sealing it.  No larvae appeared in the gauze-covered jar, even though air was present.  Maggots appeared only when flies were allowed to leave their eggs on the meat.  Redi's results were a serious blow to the long-held belief that large forms of life could arise from nonlife. Experiments of Francesco Redi References: An introduction to Microbiology , Tortora , Funke and Case, 13th Edition, Chapter 1 Microbiology by OpenStax- Rice University, 2017  Recycling Vital Elements  In the 1880s Martinus Beijerinck and Sergei Winogradsky were the first to show how bacteria help recycle vital elements between the soil and the atmosphere.  Microbial ecology, the study of the relationship between microorganisms and their environment, originated with the work of Beijerinck and Winogradsky.  Today, microbial ecology has branched out and includes the study of how microbial populations interact with plants and animals in various environments.  Among the concerns of microbial ecologists are water pollution and toxic chemicals in the environment.  Recycling Vital Elements  The chemical elements carbon, nitrogen, oxygen, sulfur, and phosphorus are essential for life and abundant, but not necessarily in forms that organisms can use.  Microorganisms are primarily responsible for converting these elements into forms that plants and animals can use.  Microorganisms, primarily bacteria and fungi, play a key role in returning carbon dioxide to the atmosphere when they decompose organic wastes and dead plants and animals.  Algae, cyanobacteria, and higher plants use the carbon dioxide during photosynthesis to produce carbohydrates for animals, fungi, and bacteria.  Nitrogen is abundant in the atmosphere but in that form is not usable by plants and animals. Only bacteria can naturally convert atmospheric nitrogen to a form available to plants and animals.  Sewage Treatment  Sewage, consists of human excrement, waste water, industrial wastes, and surface runoff.  Sewage is about 99.9% water, with a few hundredths of 1% suspended solids. The remainder is a variety of dissolved materials.  Sewage treatment plants remove the undesirable materials and harmful microorganisms. Treatments combine various physical processes with the action of beneficial microbes.  Large solids such as paper, wood, glass, gravel, and plastic are removed from sewage; left behind are liquid and organic materials that bacteria convert into such by-products as carbon dioxide, nitrates, phosphates, sulfates, ammonia, hydrogen sulfide, and methane.  Bioremediation  Some bacteria can actually use pollutants as energy sources; others produce enzymes that break down toxins into less harmful substances.  By using bacteria in these ways-a process known as bioremediation- toxins can be removed from underground wells, chemical spills, toxic waste sites, and oil spills.  In addition, bacterial enzymes are used in drain cleaners to remove clogs without adding harmful chemicals to the environment.  In some cases, microorganisms indigenous to the environment are used; in others, genetically modified microbes are used.  Among the most commonly used microbes are certain species of bacteria of the genera Pseudomonas and Bacillus. Bacillus enzymes are also used in household detergents to remove spots from clothing.  Insect Pest Control by Microorganisms  Besides spreading diseases, insects can cause devastating crop damage. Insect pest control is therefore important for both agriculture and the prevention of human disease.  The bacterium Bacillus thuringiensis has been used extensively in the United States to control such pests as alfalfa caterpillars, bollworms, corn borers, cabbageworms, tobacco budworms, and fruit tree leaf rollers.  It is incorporated into a dusting powder that is applied to the crops these insects eat. The bacteria produce protein crystals that are toxic to the digestive systems of the insects. The toxin gene has been inserted into some plants to make them insect resistant.  By using microbial rather than chemical insect control, farmers can avoid harming the environment.  Many chemical insecticides, such as DDT, remain in the soil as toxic pollutants and are eventually incorporated into the food chain.  Biotechnology o The commercial use of microorganisms to produce some common foods and chemicals. Such practical applications of microbiology are called biotechnology. o In the last several years, biotechnology has undergone a revolution through the advent of recombinant DNA technology to expand the potential of bacteria, viruses, and yeast cells and other fungi as miniature biochemical factories. Cultured plant and animal cells, as well as intact plants and animals, are also used as recombinant cells and organisms. o The applications of recombinant DNA technology are increasing with each passing year. Recombinant DNA techniques have been used thus far to produce a number of natural proteins, vaccines, and enzymes.  Gene Therapy  A very exciting and important outcome of recombinant DNA techniques is gene therapy- inserting a missing gene or replacing a defective one in human cells. This technique uses a harmless virus to carry the missing or new gene into certain host cells, where the gene is picked up and inserted into the appropriate chromosome.  Since 1990, gene therapy has been used to treat patients with adenosine deaminase (ADA) deficiency, a cause of severe combined immunodeficiency disease (SCID), in which cells of the immune system are inactive or missing; Duchenne's muscular dystrophy, a muscle-destroying disease; cystic fibrosis, a disease of the secreting portions of the respiratory passages, pancreas, salivary glands, and sweat glands; and LDL-receptor deficiency, a condition in which low-density lipoprotein (LDL) receptors are defective and LDL cannot enter cells.  Recombinant DNA technology  Beyond medical applications, recombinant DNA techniques have also been applied to agriculture. For example, genetically altered strains of bacteria have been developed to protect fruit against frost damage, and bacteria are being modified to control insects that damage crops. Recombinant DNA has also been used to improve the appearance, flavor, and shelf life of fruits and vegetables. Potential agricultural uses of recombinant DNA include drought resistance, resistance to insects and microbial diseases, and increased temperature tolerance in crops.  Microbes and Human Disease  Normal Microbiota: We all live from birth until death in a world filled with microbes, and we all have a variety of microorganisms on and inside our bodies. These microorganisms make up our normal microbiota,. The normal microbiota not only do us no harm, but also in some cases can actually benefit us.  Some normal microbiota protect us against disease by preventing the overgrowth of harmful microbes, and others produce useful substances such as vitamin K and some B vitaminsunder some circumstances normal microbiota can make us sick or infect people we contact. For instance, when some normal microbiota leave their habitat, they can cause disease  Infectious diseases  An infectious disease is a disease in which pathogens invade a susceptible host, such as a human or an animal. In the process, the pathogen carries out at least part of its life cycle inside the host, and disease frequently results.  Since 1986, local outbreaks of malaria have been identified in New Jersey, California, Florida, New York, and Texas, and the disease infects 300 million people worldwide.  In 1994, diphtheria appeared in the United States, brought by travelers from the newly independent states of the former Soviet Union, which were experiencing a massive diphtheria epidemic.  Emerging infectious diseases  A number of new diseases- emerging infectious diseases (EIDs)- have cropped up in recent years. These are diseases that are new or changing and are increasing or have the potential to increase in incidence in the near future.  Some of the factors that have contributed to the development of EIDs are- a) Evolutionary changes in existing organisms b) New geographic regions or populations by modern transportation (West Nile virus); and c) Increased human exposure to new, unusual infectious agents in areas that are undergoing ecologic changes such as deforestation and construction (e.g., Venezuelan hemorrhagic virus). d) EIDs also develop as a result of antimicrobial resistance.  Emerging infectious diseases  Avian influenza A or bird flu, caught the attention of the public in 2003, when it killed millions of poultry and 24 people in eight countries in southeast Asia.  Avian influenza viruses occur in birds worldwide.  As of 2008, avian influenza had sickened 242 people, and about half of them died. Fortunately, the virus has not yet evolved to be transmitted successfully among humans.  The U.S. Food and Drug Administration (FDA) approved a human vaccine against the avian influenza virus in April 2007. Emerging infectious diseases  In 1996, countries worldwide were refusing to import beef from the United Kingdom, where hundreds of thousands of cattle born after 1988 had to be killed because of an epidemic of bovine spongiform encephalopathy (en-sef-a-Iop'a-the), also called BSE or mad cow disease. BSE first came to the attention of microbiologists in 1986 as one of a handful of diseases caused by an infectious protein called a prion. Studies suggest that the source of disease was cattle feed prepared from sheep infected with their own version of the disease. Cattle are herbivores (planteaters), but adding protein to their feed improves their growth and health.  Creutzfeldt-Iakob disease (kroits'felt ya'kob), or CID, is a human disease also caused by a prion Emerging infectious diseases  A strain called E. coli O157:H7 causes bloody diarrhea when it grows in the intestines. This strain was first recognized in 1982 and since then has emerged as a public health problem. It is now one of the leading causes of diarrhea worldwide.  In 1996, some 9000 people in Japan became ill, and 7 died, as a result of infection by E. coli O157:H7.The recent outbreaks of E. coli 0157:H7 in the United States, associated with contamination of undercooked meat and unpasteurized beverages, have led public health officials to call for the development of new methods of testing for bacteria in food. Emerging infectious diseases  In 1995, infections of so-called flesh-eating bacteria were reported on the front pages of major newspapers. The bacteria are more correctly named invasive group A Streptococcus or IGAS. Rates of IGAS in the United States.