MIC1204 Introduction to Microbiology and Immunology PDF

MIC1204: Introduction to Microbiology and Immunology Introduction to the course. History of microbiology. Sizes in microbial world. JS Cummings  Microbiology is the study of microorganisms, a large and diverse group of m...

MIC1204: Introduction to Microbiology and Immunology Introduction to the course. History of microbiology. Sizes in microbial world. JS Cummings  Microbiology is the study of microorganisms, a large and diverse group of microscopic organisms that exist as single cells or cell clusters. Includes several classes of organisms: bacteria, archaea, algae, fungi, protozoa, and viruses (which are microscopic but not cellular). The actual inception of microbiology as a distinct science traditionally dates to the mid 1800s, when Louis Pasteur convincingly demonstrated that microorganisms were responsible for What is Microbiology? the fermentation of fluids.  Epidemic, transmissible diseases were documented in the recorded histories of early civilizations Agriculture and epizootic transmission Egyptian Plagues Greek and Roman plagues The movement of people and pathogens during renaissance explorations to African and the New World created new regional contexts for understanding disease Abiogenesis as an explanation for disease A Brief History of Optics and causality brought understanding to the field Microbiology Fig 3.1 - Opal 2009 John Snow. Not that one. In 1849, a prominent London physician, John Snow (1813–1858), published a pamphlet in which he speculated that cholera was a waterborne or foodborne, intestinal illness (Snow 1855). In so doing he directly challenged the prevailing “miasma theory” that cholera and other diseases resulted from bad air. Such thought was widely accepted at the time through traditional teachings and the influential experimental work of the German chemist Max von Pettenkoffer. In 1854 a cholera outbreak occurred in London that provided compelling evidence in favor of Snow’s alternative hypothesis. Snow carefully mapped the incident cases of cholera in the residents of downtown London and noted their proximity to public water-drawing sites. He observed that the highest incidence of disease was centered at the corner of Broad and Cambridge Streets, the site of a pumping station for drinking water. The water intake for this pump was drawn from a location just downstream of a large sewer effluent from London in the Thames River. Snow is appropriately credited as the founding father of the field of epidemiology based on this work. Louis Pasteur (1822-1895) The actual inception of microbiology as a distinct science traditionally dates to 1857, when Louis Pasteur (1822–1895) convincingly demonstrated that microorganisms were responsible for the fermentation of fluids. Pasteur’s work debunked the extant theory of “spontaneous generation” and showed instead that fermentation, spoiling, or contamination of organic substances was due to the presence of environmental microorganisms. Pasteur conducted a series of elegant and carefully executed experiments that eliminated the possibility of spontaneous generation. He showed that heat sterilization, chemical sterilization, or filtration of air and water could maintain organic materials in sterile conditions indefinitely without any microbial growth. With these investigations essentially proved the germ theory of disease and launched the field of modern microbiology. Robert Koch (1843– 1910) Studied medicine at the University at Göttingen where he came under the influence of the notable Professor of Anatomy Jakob Henle, an early proponent of the germ theory of disease, and learned the importance of careful animal experimentation in understanding disease causation. He identified anthrax bacilli (Bacillus anthracis) in the blood of infected sheep and successfully transmitted the infection into healthy experimental animals. Pioneered several new laboratory techniques including the use of single colony isolation on solid media which he called Petri dishes – Koch Plate Technique. Isolated Mycobacterium tuberculosis from infected patients. Koch’s postulates: 1. must be found in every case in which the disease occurs, 2. the pathogen must be isolated from a diseased organism and grown in pure culture, 3. the pathogen should cause the disease in animal models, 4. the same pathogen must be re-isolated from the experimental animal. Fundamental Differences Between Koch and Pasteur Diagram of Eukaryotic Cell Optics Given that individual microbes cannot be observed with the unaided human eye, microscope technology has been developed to support the field. Our understanding of microbes and microbial diseases expands every time a new imaging technology is introduced to the field. There are several types of microscopes with differing resolving power (resolution), this is defined as the distance that must separate two point sources of light if they are to be seen as two distinct images. Types include: Light Electron Confocal scanning Scanning probe MIC1204 – Introduction to Microbiology and Immunology Light Microscopy The resolving power of the light microscope under ideal conditions is about half the wavelength of the light being used. With yellow light of a wavelength of 0.4 mm, the smallest separable diameters are thus about 0.2 mm (ie, one third the width of a typical prokaryotic cell). The useful magnification of a microscope is the magnification that makes visible the smallest resolvable particles. Several types of light microscopes are commonly used in microbiology including: Bright Field microscope Phase Contrast microscope Dark Field microscope Fluorescence microscope Light Microscope Imagery Electron Microscopy The high resolving power of electron microscopes has enabled scientists to observe the detailed structures of prokaryotic and eukaryotic cells. The superior resolution of the electron microscope is due to the fact that electrons have a much shorter wavelength than the photons of white light. There are two types of electron microscopes in general use: the transmission electron microscope (TEM), which has many features in common with the light microscope, and the scanning electron microscope (SEM). The TEM was the first to be developed and uses a beam of electrons projected from an electron gun and directed or focused by an electromagnetic condenser lens onto a thin specimen. As the electrons strike the specimen, they are differentially scattered by the number and mass of atoms in the specimen; some electrons pass through the specimen and are gathered and focused by an electromagnetic objective lens, which presents an image of the specimen to the projector lens system for further enlargement. TEM can resolve particles 0.001 mm apart. The SEM generally has a lower resolving power than the TEM; however, it is particularly useful for providing three dimensional images of the surface of microscopic objects Microbial Sizes Seeing is Believing Bacterial classification can include a description of the physical shape of the bacterium as observed under microscope. Where That Leaves Us Microorganisms are the products of evolution, the biologic consequence of natural selection operating on a vast array of genetically diverse organisms. It is useful to keep the complexity of natural history in mind before generalizing about microorganisms, the most heterogeneous subset of all living creatures. A major biologic division separates the eukaryotes, organisms containing a membrane-bound nucleus, from prokaryotes, organisms in which DNA is not physically separated from the cytoplasm. Further major distinctions can be made between eukaryotes and prokaryotes. Eukaryotes, for example, are distinguished by their relatively large size and by the presence of specialized membrane-bound organelles such as mitochondria. Eukaryotic microorganisms—or, phylogenetically speaking, the Eukarya—are unified by their distinct cell structure and phylogenetic history. Among the groups of eukaryotic microorganisms are: the algae, the protozoa, the fungi, and the slime molds. Looking Forward Perhaps no other developments have had such a major impact on the health and welfare of humankind than those comprising the history of microbiology and immunology. Over the last 100 years, the mortality burden of infectious diseases has decreased substantially, and the average lifespan has increased by over 30 years due to advances in public health, sanitation, vaccines, and anti-infective chemotherapy – all deriving from the sciences of microbiology and immunology (Centers for Disease Control 1999). Future advances are anticipated when the genomics era in which we now live, and the promise of systems biology and personalized medicine are fully realized in the next few decades. A remarkable story of directed inquiry into the fundamental nature of microbes and immune defenses preceded many of the current advances in medicine. Much work remains before the benefits of these discoveries can be applied equally worldwide. Conclusion Class administration will follow familiar track. Microbiology is the study of very small organisms and biologically relevant non-living entities. The study of diseases and development of germ theory were intrinsic to development of the field. Description of microbes was limited by available optical technologies. Nomenclature of microbes are often reflective of optical observations.