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Microbiology: Chapter 1: The Microbial World and You The study of microorganisms. Microorganisms : Small living organisms that generally can not be seen with the naked eye. Include: uBacteria uFungi (yeasts and molds) uProtozoa uAlgae uMulticellular parasites Also include nonliving infectious agents: ♦Viruses ♦ Prions Microbes are Essential for Life on Earth: Have many important and beneficial biological functions: u Photosynthesis: Algae and some bacteria capture energy from sunlight and convert it to food, forming the basis of the food chain. u Decomposers: Many microbes break down dead and decaying matter and recycle nutrients that can be used by other organisms. u Nitrogen Fixation: Some bacteria can take nitrogen from air and incorporate it into soil. I mportant and beneficial biological I mportant and beneficial biological functions of Microbes: u Digestion: Animals have microorganisms in their digestive tract, that are essential for digestion and vitamin synthesis. u Cellulose digestion by ruminants (cows, rabbits, etc.) u Vitamin K and B synthesis in humans. u Medicine: Many antibiotics and other drugs are naturally synthesized by microbes. u Penicillin is made by a mold. I mportant and beneficial biological functions of Microbes: functions of Microbes: u Food Industry: Many important foods and beverages are made with microbes: u Genetic Engineering: Recent advances in gene splicing allow us to design recombinant microbes that produce important products: u Alcoholic beverages (Wine, beer, rum, whiskey) u Bread u Vinegar u Soy sauce u Cheese u Pickles, olives, sauerkraut u Yogurt u Buttermilk u Sour cream u Coffee u Chocolate u Hams, sausages u Human growth hormone (Dwarfism) u Insulin (Diabetes) u Blood clotting factor (Hemophilia) u Recombinant vaccines uHepatitis A and B vaccines u Human hemoglobin (Emergency blood substitute) u Taxol (Breast and ovarian cancer) u Erythropoietin (Anemia) u Monoclonal antibodies (Disease diagnosis and prevention). 1 I mportant and beneficial biological functions of Microbes: u Medical Research: Microbes are well suited for biological and medical research for several reasons: u Relatively simple and small structures, easy to study. u Genetic material is easily manipulated. u Can grow a large number of cells very quickly and at low cost. uShort generation times make them very useful to study genetic changes. Microbes and Disease: Most microbes are either beneficial or harmless to humans. u Less than 1% of microbes cause disease. u In 1962, the surgeon general of the United States stated: “The war against infectious diseases has been won”. uToday it is clear that this was overly optimistic: u Emerging diseases: New diseases like AIDS, hantavirus, Ebola fever, Lyme disease, Hepatitis C, and others that did not exist a few years ago. u Antibiotic and Drug Resistance: Many old diseases are becoming resistant to traditional therapies: Tuberculosis, gonorrhea, malaria, etc. u Today infectious diseases cause 50% of the 52 million worldwide deaths per year. Infectious Diseases Causing Most Deaths Worldwide in 1998 Disease Cause Deaths/year Acute Respiratory*Bacterial or viral 4,400,000 Diarrheal diseases Bacterial or viral 3,200,000 Tuberculosis Bacterial 3,100,000 Malaria Protozoan 3,100,000 Hepatitis B Viral 2,000,000 Measles Viral 1,500,000 AIDS Viral 1,000,000 Neonatal Tetanus Bacterial 600,000 *: Pneumonia, bronchitis, influenza, etc. Neonatal tetanus kills over 600,000 infants every year. Source: Tropical Medicine and Parasitology, 1997. Microbes and Disease in Human History 4 Bubonic Plague (Black death): Several devastating epidemics throughout history. • High mortality: Up to 80% of those infected die. • 1347-1351: Over 75 million died in Europe, Asia, and Africa. • Over 25% of population of Europe died. • Cause was unknown for over 500 years, leading to superstition, persecution, and hysteria. • Bacterial disease transmitted by rat fleas. • Rare today but still occurs: • 10-15 cases/year in U.S. • Last epidemic occurred in India in 1994. Left: Swollen lymph nodes in bubonic plague infection. Right: Infected flea bite with eschar and carbuncle. Source: Tropical Medicine and Parasitology, 1997. 2 Worldwide Distribution of Plague 4 Smallpox: One of deadliest human infectious diseases throughout history. • Caused by smallpox virus. • First known case in 1175 B.C.: Egyptian pharaoh Ramses V died from smallpox. • Several hundred million deaths through history. • Up to 90% of Native American population was killed by smallpox and other diseases (measles and plague) introduced during European conquests. ++: Frequent transmission +/-: Infrequent transmission. Source: Tropical Medicine and Parasitology, 1997. • Native population of Central and South America dropped from 130 million to about 1.6 million over several decades. • Smallpox was used as a biological weapon by British colonists in North America. • 600,000 deaths/year in Europe from 1500-1700. 4 Smallpox (Continued) • 75% of survivors were severely scarred and/or blinded. • An effective vaccine was developed in 1870s by Edward Jenner, using a related virus (cowpox). • Smallpox was the first and only viral disease to be completely eradicated (1977). • Worldwide immunization campaign in 1960s. • Only infects humans. Smallpox infection in a small child. Disease was eradicated worldwide by immunization in 1977. Source: Microbiology Perspectives, 1999. 4Tuberculosis (TB): Caused by a bacterium that mainly infects lungs but may spread to other parts of body. • Leading killer of world’s infectious diseases: • 3 million die worldwide every year. • Over 1 million killed in U.S. between 1930 -49. • One out of three people infected worldwide. • In U.S. 10 million people are presently infected, but only 5% will develop active disease. • Most healthy individuals can contain infection. • Treatment: Antibiotics for up to one year. • After introduction of antibiotics, TB declined from 1950s to 80s, and then started to increase again. • Low patient compliance with treatment has caused antibiotic resistant TB . • AIDS epidemic has caused an increase in cases. Tuberculosis is leading killer among infectious diseases worldwide. Patient with lymph node necrosis. Photo by Dr. I. Small 3 4 Childbirth Fever: Common nosocomial (hospital acquired) infection. • Bacterial infection of the uterus as a result of childbirth or abortion. • Transmitted by hands and instruments of physicians and midwives. • Extremely common before the 1900s. • About 1 in 17 women who gave birth would become infected (fever, chills, delirium, and death). • Cause was unknown. • Austrian doctor Semmelweiss showed that washing hands and instruments with a disinfectant solution greatly reduced cases. • Today common in women who have illegal abortions, especially in third world countries. African AIDS patient with slim disease Source: Tropical Medicine and Parasitology, 1997 Extensive symmetric tumor lesions of Kaposis’s sarcoma in an AIDS patient. Source: AIDS, 1997 4 AIDS: Acquired Immune Deficiency Syndrome. • First cases reported in 1981 at UCLA. • Cause: Human Immunodeficiency Virus (HIV) • Transmitted by sexual contact, blood transfusions, mother-to-child, and infected needles. • Destroys an individual’s immune system, making them susceptible to many infectious diseases and cancer. • Number of cases has grown rapidly during the last two decades. As of 2001: • Over 900,000 infected individuals in the U.S. • Over 40 million deaths worldwide. Endemic Kaposi’s Sarcoma, nodular form in an AIDS patient. Source: AIDS, 1997. Oral candidiasis (yeast infection) in an AIDS patient Source: Atlas of Clinical Oral Pathology, 1999 4 History of Microbiology Early Studies History of Microbiology Spontaneous Generation vs Biogenesis Before 17th century, study of microbiology was hampered by the lack of appropriate tools to observe microbes. u Robert Hooke: In 1665 built a compound light microscope and used it to observe thin slices of cork. Coined the word cell. u Anton van Leeuwenhoeck : In 1673 was the first person to observe live microorganisms which he called “ animalcules” (bacteria, protozoa), using single-lens microscopes that he designed. u Before 1860s many scientists believed in History of Microbiology Spontaneous Generation vs Biogenesis History of Microbiology Spontaneous Generation vs Biogenesis Spontaneous generation, i.e.: That living organisms could arise spontaneously from nonliving matter: u Mice come from rags in a basket. u Maggots come from rotting meat. u Ants come from honey. u Microbes come from spoiled broth. 4 Theory of Biogenesis: Belief that living cells can Debate was finally settled by Pasteur. only arise from other living cells. u Francesco Redi : In 1668 proved that maggots do not arise spontaneously from decaying meat. u Lazaro Spallanzani: In 1765 found that nutrient broth that had been heated in a sealed flask would not become contaminated with microbes. u Louis Pasteur: In 1861 finally disproved u Some proponents of spontaneous generation argued that boiling had destroyed the “life force” of air in flask. u Others argued that microbes were different from other life forms. History of Microbiology Golden Age: 1857-1914 Rapid advances led to the development of microbiology as a science. Pasteur’s Contributions to Microbiology: u Fermentation: Pasteur found that yeasts were responsible for converting sugar into alcohol in the absence of air. u Souring and spoilage were caused by bacterial contamination of beverages. spontaneous generation when he demonstrated that microorganisms in the environment were responsible for microbial growth in nutrient broth. u Designed swan neck flasks that allowed air in, but trapped microbes in neck. u Developed aseptic technique: Practices that prevent contamination by unwanted microorganisms. History of Microbiology Golden Age: 1857-1914 Pasteur’s Contributions: u Pasteurization: Developed a process in which liquids are heated (at 65 o C) to kill most bacteria responsible for spoilage. u Disease Causes: Identified three different microbes that caused silkworm diseases. u Vaccine: Developed a vaccine for rabies from dried spinal cords of infected rabbits. u Directed Pasteur Institute until his death in 1895. 5 History of Microbiology Golden Age: 1857-1914 History of Microbiology Golden Age: 1857-1914 Germ Theory of Disease: Belief that microbes cause diseases. Before, most people believed diseases were caused by divine punishment, poisonous vapors, curses, witchcraft, etc. Germ Theory of Disease: u Agostino Bassi (1835): Found that a fungus was u Robert Koch (1876): First person to conclusively responsible for a silkworm disease. u Ignaz Semmelweis (1840s): Demonstrated that childbirth fever was transmitted from one patient to another, by physicians who didn’t disinfect their hands. He was ostracized by colleagues. History of Microbiology Modern Microbiology: After 1914 u Joseph Lister (1860): Used disinfectant to treat surgical wounds, greatly reducing infection rates. Considered the father of antiseptic surgery. prove that a specific bacterium caused a disease. u Germ Theory: One microbe causes one specific disease. u Proved that Bacillus anthracis causes anthrax in cattle. u Later identified bacterium that causes tuberculosis. History of Microbiology Modern Microbiology: After 1914 Chemotherapy: Treatment of a disease by using a chemical substance. Chemical must be more poisonous to microbe than host. u Paul Ehrlich (1910): Search for “magic bullet”. u Quinine: First known chemical to treat a disease u Alexander Fleming (1928): Discovered that (malaria). Used by Spanish conquistadors. u Synthetic Drugs: Made in the laboratory. u Antibiotics: Produced naturally by fungi and bacteria. u Discovered salvarsan, an arsenic derivative, was effective against syphilis. penicillin produced by the mold Penicillium notatum was able to prevent microbial growth. u Penicillin was not mass produced until the 1940s. u Rene Dubos (1939): Discovered two antibiotics (gramidin and tyrocidine) produced by bacterium (Bacillus brevis). History of Microbiology Modern Microbiology: After 1914 Diversity of Microorganisms I. Bacteria (Sing. Bacterium) Problems with Chemotherapy: u Small, single-celled (unicellular) organisms. u Toxicity u Procaryotes: “Before nucleus”. u Drug resistant microbes Lack the following structures: u Nuclear membrane around DNA u Membrane bound organelles uMitochondria uChloroplasts uGolgi apparatus uEndoplasmic reticulum uLysosomes 6 Kingdom Prokaryotae: Bacteria lack nucleus and membrane bound organelles Diversity of Microorganisms I. Bacteria (Sing. Bacterium) u Include two groups: u Eubacteria: Peptidoglycan cell walls. u Archaebacteria: Lack peptidoglycan cell walls. u Shapes: Several forms: u Bacilli : Rod like. (Sing. Bacillus) u Cocci: Spherical. (Sing. Coccus) u Spiral: Corkscrew or curved u Square u Star shaped Diversity of Microorganisms I. Bacteria (Sing. Bacterium) u Divide by binary fission (not mitosis). u Source of nutrients varies: u Heterotrophs : Consume organic chemicals. u Autotrophs : Make their own food. Include photosynthetic bacteria. u Motility: Many can “swim” by using moving appendages: u Cilia: Small hair like structures u Flagella: Large whip like structures. u Distinguish between motility and Brownian motion. Diversity of Microorganisms II. Fungi (Sing. Fungus) u Source of nutrients varies: u Saprotrophs : Decomposers that feed on dead and decaying matter. Most fungi are decomposers. u Parasites: Obtain nourishment by parasitizing live animals and plants. Diversity of Microorganisms II. Fungi (Sing. Fungus) u Eucaryotes: “True nucleus” u DNA is surrounded by nuclear membrane. u Cells have membrane bound organelles: Mitochondria, endoplasmic reticulum, etc. u Cells are larger than those of procaryotes. u May be unicellular or multicellular: u Unicellular: Yeasts u Multicellular: Molds, mushrooms u Do not carry out photosynthesis. u Must absorb organic nutrients from their environment. Diversity of Microorganisms III. Protozoa (Sing. Protozoan) u Eucaryotes: “True nucleus” u DNA is surrounded by nuclear membrane. u Cells have membrane bound organelles and are larger than those of procaryotes. u Unicellular u Cell wall made of chitin. u Kingdom Protista u May reproduce sexually or asexually. u Sexual or asexual reproduction u Classified based on locomotion: u Pseudopods : “False feet”. Cytoplasmic extensions. uExample: Amoeba 7 Protozoa Belong to Kingdom Protista: Eucaryotic Unicellular or Simple Multicellular Organisms Diversity of Microorganisms III. Protozoa (Sing. Protozoan) u Classified based on locomotion: u Flagella: Long whip like appendages. uExample: Trichomonas vaginalis, causes trichominiasis, a sexually transmitted disease. u Cilia: Small hair like appendages u Nonmotile: Do not move in their mature forms. uExample: Plasmodium spp., causative agent of malaria. Diversity of Microorganisms IV. Algae (Sing. Alga) u Eucaryotes: “True nucleus” u Photosynthetic: Important part of food chain because produce oxygen and carbohydrates used by animals. u Unicellular or multicellular u Kingdom Protista u Sexual or asexual reproduction u Cell walls composed of cellulose u Found in aquatic environments (oceans, lakes, rivers), soil, and in association with plants. Comparison of Cells and Viruses Diversity of Microorganisms V. Viruses u Acellular infectious agents, not considered living because they lack cells. u Obligate intracellular parasites: Viruses can only reproduce by using the cellular machinery of other organisms. u Simple structure : u Protein coat (capsid) with either DNA or RNA, but not both. u May also have a lipid envelope. Diversity of Microorganisms VI. Multicellular Animal Parasites u Eucaryotes: “True nucleus” u Multicellular animals, usually are visible to the naked eye. u Microscopic during some stages of life cycle. u Spend part or all of their lives inside an animal host. u Helminths include: u Flatworms (Platyhelminths ): E.g. Tapeworm u Roundworms (Nematodes): E.g. Ascaris, pinworm. 8