Module 1: Introduction to Microbiology PDF

MCB 11 MODULE 1: INTRODUCTION TO MICROBIOLOGY FIRST SEMESTER | BS BIOLOGY ‘24 | MCB 11 | MS. DOMINI THERESA PECUNDO MICROBIOLOGY Based on...

MCB 11 MODULE 1: INTRODUCTION TO MICROBIOLOGY FIRST SEMESTER | BS BIOLOGY ‘24 | MCB 11 | MS. DOMINI THERESA PECUNDO MICROBIOLOGY Based on the old definition, microbiology is the study of organisms and agents that are too small to be seen by the naked eye (< 1mm). Based on the new definition, microbiology is the study of organisms that can exist as single cells (other are acellular), contain a nucleic acid genome for at least some part of their life cycle, and are capable of replicating that genome. BIOGENESIS THEORY The science of microbiology revolves around two interconnected themes: Life begets life. ○ Understanding - to understand the living world Francesco Redi (1668) - demonstrated that maggots do not of microscopic organisms (as a basic biological arise from decaying meat and are produced from the eggs of science). flies. ○ Application - to apply our understanding of microbial life processes for the benefit of humankind and planet Earth (as an applied biological science). Basic microbiology refers to the interest in specific group of microorganisms and their biology: ○ Virology (Viruses) ○ Mycology (Fungi) ○ Phycology (Algae) ○ Bacteriology (Bacteria) ○ Protozoology (Protozoa) Lazzaro Spallanzani (1768) - boiled broth mixture in a sealed container to avoid contamination, leading to no microbial MODERN MICROBIOLOGY growth. Zacharias Janssen (1597) - invented the first compound microscope (3-10x). Athanasius Kirche - suggested to be the first one to observe a microorganism. Antonie van Leeuwenhoek (1676) - used a single lens microscope to observe bacteria and protozoa. Robert Hooke (1665) - developed a simple compound microscope. SPONTANEOUS GENERATION THEORY Franz Schultze - demonstrated that when air was bubbled through sulfuric acid, the resulting air did not produce Life emerges from non-living matter with “vital force”. microbial growth due to sterilized culture media. John Needham (1745) - boiled broth mixture and then Theodor Schwann - passed air through red hot tubes, which cooled it with an open container; causing microbial lead to purifying the air. growth. 1  George Friedrich Schröder and Theodor von Dusch (1850) - Louis Pasteur - showed that the pébrine disease of silkworms allowed air to enter a flask of heat sterilized medium after the was caused by a protozoan (e.g. Nosema bombycis). air had passed through a sterile cotton wool. This led to no Robert Koch (1843-1910) - established the relationship microbial growth. between Bacillus anthracis and anthrax (disease). Louis Pasteur - by sterilization of broth mixture in heated swan-neck flasks, no contamination occurred as the moisture KOCH’S POSTULATES from condensation created a surface tension inhibiting microbial growth from entering the flask. Koch’s postulates are four criteria designed to establish a causal relationship between a causative microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890. Koch’s (4) postulates are the following: ○ The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. ○ The microorganism must be isolated from a diseased organism and grown in pure culture. ○ The cultured microorganism should cause disease when introduced into a healthy organism. ○ The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent. John Tyndall - discovered that both mixtures can contain heat-resistant microbes (endospores). Also developed a process to sterilize growth media to kill the heat-resistant microbes; tyndallization. GERM THEORY OF DISEASE Diseases are caused by specific agents called germs. Girolamo Fracastoro (1478-1553) - disease was caused by invisible living creatures. Agostino Bassi (1773-1856) - showed that a disease of silkworms was caused by a fungus (Beauveria bassiana). Miles Joseph Berkley (ca. 1845) - demonstrated that the Great Potato Blight of Ireland was caused by a fungus (Phytophthora infestans) Heinrich Anton de Bary (1853) - showed that smut and rust fungi caused cereal crop diseases. Known as the “Founding Father of Plant Pathology”. KOCH’S POSTULATES LIMITATIONS Ignaz Philipp Semmelweis (1861) - asepsis in obstetric wards to prevent the transmission of childbed fever from patient to Causative agents of several human diseases do not cause patient. Known as the “Savior of Mothers”. disease in any known experimental animal. ○ Made a policy for all attending physicians to wash their Some microbes are obligate intracellular parasites (like hands with chlorinated lime solutions (calcium chlamydia and viruses) and are very challenging or even hypochlorite) between patients. impossible to grow on artificial media. ○ Mortality rate dropped from 18% to 2.4%. Some diseases (such as tetanus) have variable signs and Joseph Lister (1867) - provided indirect evidence that symptoms between patients. microorganisms were the causal agents of disease. Known as Some diseases (such as pneumonia and nephritis) may be the “Father of Antiseptic Surgery”. caused by a variety of microbes. ○ Used phenol/carbolic acid in surgical dressings and heat Some pathogens can cause several diseases. sterilized surgical instruments. 2  Certain pathogens (such as HIV) cause disease in humans only. Sergei Winogradsky (1856-1953) and Martinus Beijerinck It is unethical to purposely infect a human. (1851-1931) - studied soil and soil microorganisms. Also developed enrichment cultures and selective media. VACCINE DEVELOPMENT VARIOLATION ○ Beijerink discovered nitrogen fixation. ○ Winogradsky discovered lithotrophy and chemoautotrophy. Edward Jenner (ca. 1798) - used a vaccination procedure to protect individuals from smallpox. ○ Used pus from cowpox blisters to inoculate. ○ Cowpox virus is closely related to variola, the causative agent of smallpox. Pasteur and his co-workers - developed vaccines for chicken cholera, anthrax, and rabies (attenuation). ○ Incubation of cultures for long intervals between transfers caused pathogens to lose their ability to cause disease. ○ Growing the pathogen in an unnatural host weakens it; attenuation. VIRUS DISCOVERY Charles Chamberland (1851-1908) - developed porcelain bacterial filters that had tiny pores that allowed fluids to pass through while holding back bacteria and other microorganisms. Martinus Beijerink - in 1868, he published results on filtration experiments demonstrating that tobacco mosaic disease is caused by an infectious agent smaller than a bacterium, which he called “virus”. ○ Considered one of the founders of virology. ANTIMICROBIAL COMPOUND DISCOVERY Paul Ehrlich - developed 606ᵗʰ compound SALVARSAN (organic arsenical to treat syphilis). Alexander Fleming - discovered the “miracle drug“ penicillin from Penicillium. It is used to treat infections caused by bacteria. FERMENTATION AND PASTEURIZATION Louis Pasteur - demonstrated the role of yeasts in fermentation. ○ Fermentations were the results of microbial activity; such as alcohol fermentation by yeasts and lactic acid fermentation by bacteria. ○ Developed a process of pasteurization to preserve wine. Eduard Buchner - fermentation could occur in yeast extract free of cells; cell-free extract or “juice”. MICROBIAL ECOLOGY 3