Chapter 1 MicrobiologyThe Science What Is Microbiology Biology

Chapter 1: Microbiology—The Science

What Is Microbiology? • Biology is the study of living organisms. • Microbiology is an advanced biology course. • Microbiology is the study of microbes, which are extremely small (microscopic) living organisms and certain nonliving entities. • Living microbes are known as cellular microbes or microorganisms; examples include bacteria, archaea, some algae, protozoa, and some fungi. • Nonliving microbes are known as acellular microbes or infectious particles; examples include viroids, prions, and viruses. • Microbes are ubiquitous (i. e. , they are found virtually everywhere).

Acellular and Cellular Microbes

What Is Microbiology? (cont. ) • The microbes that cause disease are sometimes referred to as “germs. ” • The scientific term for disease-causing microbes is pathogens. • Microbes that do not cause disease are called nonpathogens • The vast majority of microbes are nonpathogens.

What Is Microbiology? (cont. ) Microbes that live on and in our bodies are referred to as our indigenous microbiota • Most of these are beneficial by preventing pathogen growth or secreting beneficial materials • i. e. E. coli • Lives in human intestinal tract • Produces Vitamin K and B 1 • Some members of our indigenous microbiota are opportunistic pathogens • Opportunistic pathogens are microbes that can cause disease, but usually do not; they can be thought of as microbes that are awaiting the opportunity to cause disease •

Microbial Disease • Two categories of microbial disease • • Infections disease • Results when a pathogen colonizes the body and subsequently causes disease • The leading cause of disease in the world and third leading cause of death in the US Microbial intoxication • When a person that ingests a toxin (poisonous substance) that has been produced by a microbe • Most heat treatment kills microbes, but the toxin remains

Categories of Diseases Caused by Pathogens

Why Study Microbiology? • Microbes play significant roles in our lives; they are essential for life on this planet. • Photosynthetic algae and bacteria (such as cyanobacteria) produce much of the oxygen in our atmosphere. • Microbes contribute more oxygen to our atmosphere than plants • Microorganisms are involved in the decomposition of dead organisms and waste products. • Saprophytes are organisms that live on dead and/or decaying organic matter. • • Aids in fertilization The use of microbes to clean up toxic wastes and other industrial waste products is known as bioremediation. • Usually these are genetically engineered

Microbes as Saprophytes

Why Study Microbiology? (cont. ) • Algae and bacteria serve as food for tiny animals; they are important links in food chains. • Plankton serves as the starting point for many food chains • Microbes that live in the intestinal tracts of animals aid in the digestion of food and produce beneficial substances. • For many years, microorganisms have been used as “cell models”; the more the scientists learned about microbial cells, the more they learned about cells in general.

Microbes and the Food Chain

Microbes and Nitrogen Fixation • Many microbes play essential roles in various elemental cycles, such as the carbon, nitrogen, oxygen, sulfur, and phosphorus cycles. • Important to farms and replenishment of nutrients by the breakdown of organic material into inorganic nutrients

Why Study Microbiology? (cont. ) • Microbes are used in many industries, such as food, beverage, chemical, and antibiotic industries and in genetic engineering. • • In genetic engineering, a gene(s) from one organism is inserted into a bacterial or yeast cell; the cell that receives the new gene(s) is then capable of producing the gene product(s) coded for by the new gene(s). • • Antibiotic—substance produced by a microbe effective in killing or inhibiting the growth of other microbes Allows for insulin, vaccines, growth hormones, etc. production The use of living organisms or their derivatives to make or modify useful products or processes is called biotechnology.

Infectious disease and health care

First Microorganisms on Earth • Fossils of primitive microorganisms date back about 3. 5 billion years. • Candidates for the first microorganisms on Earth are archaea and cyanobacteria. • Infectious diseases of humans and animals have existed for as long as humans and animals have inhabited the planet. • Earliest known account of pestilence occurred in Egypt in about 3180 BC.

Pioneers in the Science of Microbiology Anton van Leeuwenhoek (1632– 1723) ● “Father of Microbiology” ● Not a trained scientist! ● Made many simple single-lens microscopes as a hobby – the skill was lost when he died ● Observed “animalcules” (bacteria and protozoa) ● Examined any sample he could ● Send observations to Royal Society of London ● In late 17 th century, he convinced scientist of the existence of microbes

Origins of Microbes • Abiogenesis • Theory of Spontaneous generation • Life can arise spontaneously from non-living material • • • Decaying corpses, soil and swamp gases Debated for 200 years before being disproved and replaced with biogenesis Biogenesis • Life can only arise from preexisting life • Proposed by Rudolf Virchow

Pioneers in the Science of Microbiology (cont. ) Louis Pasteur (1822– 1895) • French chemist who made numerous contributions to microbiology • Considered to be the founder of microbiology and a cornerstone of modern medicine • Investigated different fermentation products • Developed the pasteurization process • Heating liquid to a desired temperature for a set amount of time to kill pathogens • Helped disprove theory of spontaneous generation • Discovered life forms that could exist without oxygen • Anaerobes – organisms that do not require oxygen • Aerobes – organisms that require oxygen

Pioneers in the Science of Microbiology (cont. ) • Louis Pasteur (1822– 1895) • • Developed several vaccines • Chicken cholera • Anthrax • Swine erysipelas • Rabies Prevent Rabies in dogs • Treat rabies in humans Contributed to the germ theory of disease • • • The theory that specific microbes cause specific infections Helped bring about changes in hospitals to prevent the spread of disease

Pioneers in the Science of Microbiology (cont. ) Robert Koch (1843– 1910) German physician who made numerous contributions to microbiology Made significant contributions to the germ theory of disease Discovered that Bacillus anthracis produced spores Developed methods of fixing and staining bacteria Developed methods to cultivate bacteria on solid media Allowed for the growth of pure cultures Discovered the bacterium that causes TB and cholera His findings led to the development of the TB skin test Developed Koch’s postulates Experimental procedure to prove a specific microbe causes a specific infection

Koch’s Postulates A particular microbe must be found in all cases of the disease and must not be present in healthy animals or humans. 2. The microbe must be isolated from the diseased animal or human and grown in pure culture in the laboratory. 3. The same disease must be produced when microbes from the pure culture are inoculated into healthy susceptible laboratory animals. 4. The same microbe must be recovered from the experimentally infected animals and grown again in pure culture. 1.

Koch’s Postulates (cont. )

Koch’s Postulates (cont. ) • If an organism fulfills Koch’s Postulates, it has been proven to be the cause of that particular infectious disease. • Koch’s Postulates helped prove the germ theory of disease. • Koch gave a tremendous boost to the development of microbiology by stressing laboratory culture and identification of microorganisms. • Circumstances do exist in which Koch’s Postulates cannot be fulfilled.

Exceptions to Koch’s postulate • Obligate intracellular pathogens • Species specific pathogens • Synergistic or polymicrobial infections • Pathogen alterations in vitro • Diseases not caused by microbes

Careers in Microbiology • A microbiologist is a scientist who studies microbes. • There are many career fields within the science of microbiology (e. g. , bacteriology, phycology, protozoology, mycology, parasitology, and virology). • Medical microbiology – Involves the study of pathogens, the disease they cause, and the body’s defenses against disease – Concerned with epidemiology, transmission of pathogens, diseaseprevention measures, aseptic techniques, treatment of infectious diseases, immunology, and production of vaccines