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Lecture 1 Introduction, History and Microscopy Text Chapters: 1.1-1.8; 4.1-4.3 Introduction to Microbiology • What is Microbiology? • What do we know about Microbiology? • Group task (Let’s have fun discussion!!) :3-4 students sit as a group and discuss about microbiology and fill in the worksheet with any words starting with given alphabet. Introduction: Definitions • Microorganisms – Organisms that are distinct form macroorganisms – Diverse group – Exist as single cells (unicellular) or in cell clusters (multicellular) • Microbiology – The basic science of understanding microbial life – The applications of science to human needs. Introduction: The importance of Microbiology • Microorganisms are excellent models for understanding cell function in higher organisms, including humans. • Because microorganisms are central to the very functioning of the biosphere, the science of microbiology is the foundation of all the biological sciences Introduction: Examples for Microorganisms Examples of single microbial cell Purple bacteria First phototroph on earth Cyanobacteria First oxygen evloving phototroph Microorganisms Can Appear in Masses: Bloom of Purple Bacteria Microorganisms in Culture History: The First Description of Microorganisms • Robert Hooke observed fruiting structures of molds in 1665 and was the first to describe microorganisms (Figure 1.8). Adjustment Lens History: The First Description of Bacteria • Antoni van Leeuwenhoek was the first to describe bacteria in 1676 (Figure 1.9). – The field of microbiology was unable to develop until Leeuwenhoek constructed microscopes that allowed scientists to see organisms too small to be seen with the naked eye. Van Leeuwenhoek’s Microscope Van Leeuwenhoek’s drawing on various organsisms Blood Smear Viewed through van Leeuwenhoek’s Microscope Erythrocytes Leukocyte History:The Concept of Biogenesis Replaces Spontaneous Generation Theory • Spontaneous generation claims that life can originate from non-living matter. • Biogenesis states that living cells originate from living cells. • Louis Pasteur's disproved spontaneous generation. • His work led to the development of methods for controlling the growth of microorganisms. Pasteur’s Swan Neck Experiment History: Pasteur’s Conclusions • The bended neck allowed air to enter the bottle and the liquid but trapped any particulates including microorganisms. • No microbial growth as long as the liquid broth did not come in contact with the microbes. • Hence air alone was not sufficient to generate life. History: Microorganisms Cause Disease • Robert Koch developed a set of postulates (Figure 1.12) to prove that a specific microorganism causes a specific disease. – B. anthracis causes anthrax – M. tuberculosis causes tuberculosis Koch’s Postulates • The suspected pathogenic organism should be present in all cases of the disease and absent from healthy animals. • The suspected organism should be grown in pure culture—that is, a culture containing a single kind of microorganism. • Cells from a pure culture of the suspected organism should cause disease in a healthy animal. • The organism should be reisolated and shown to be the same as the original. History: Microbial Diversity and Geochemical Cycling • Beijerinck and Winogradsky – Late 19th century – Studied bacteria in soil and water • Beijerinck – Developed the enrichment culture technique for the isolation of representatives of various physiological groups • Winogradsky – Biogeochemical cycling History: Host Defense against Microbes • Ehrlich: Magic Bullet (antibodies) • Metchnikoff: Phagocytosis • Fleming: Lysozyme History: Antimicrobial Drugs Discovery of Penicillin Sir Alexander Fleming Modern Era of Microbiology • Applied microbiology : agricultural, soil, marine • Basic microbiology : microbial systems, biochemistry, genetics • Molecular microbiology : biotechnology, genomics • In the middle to latter part of the 20th century, basic and applied microbiology worked hand in hand to usher in the current era of molecular microbiology. Landmarks in Microbiology MICROSCOPY • Microscopes are essential for microbiological studies • Light microscopes: cellular resolution – – – – bright-field (stains) dark-field phase contrast fluorescence (stains) • Electron microscopes: subcellular resolution Light Microscopy: Optics • Visualization depends on magnification (lenses) and resolution (physical properties of light) • The limit of resolution for a light microscope is about 0.2 m (or 200 nm) – Objects closer than 0.2 m cannot be resolved • Total magnification is product of the magnification of its ocular and its objective lenses Microscopy: Stains • Staining (Figures 4.3, 4.4) is used to increase contrast in bright-field microscopy – Simple: one dye stains all cells – Differential: combination of dyes allows differential staining of different populations Simple Stain Differential Stain Example for Gram Stain E. coli (g-) S. aureus (g+) Microscopy: Dark Field • Greater resolution • Light reaches specimens only from the side • Only the specimen itself is illuminated Candida sp. Treponema pallidum Microscopy: Phase Contrast • May be used to visualize live samples and avoid distortion from cell stain • Image contrast is derived from the differential refractive index of cell structures. Microscopy: Fluorescence • Visualization of autofluorescent cell structures (e.g., chlorophyll) or fluorescent stains • Can greatly increase the resolution of cells and cell structures • Many functional probes available Example for Differential Fluorescence Stain Psuedomonas (green) Bacillus (orange) Microscopy: Electron Microscopy • Electron microscopes have far greater resolving power than light microscopes, with limits of resolution of about 0.2 nm • Two major types of electron microscopes – Transmission electron microscopy (TEM) for observing internal cell structure down to the molecular level – Scanning electron microscopy (SEM) for 3-D imaging and examining surfaces Electron Microscopy TEM Pseudomonas SEM Mycobacterium Additional Resources • http:// www.millenniumark.net/News_Files/Newsletters/News010106_30f5NCB/A nthrax.hand.gif • http://pathmicro.med.sc.edu/ghaffar/anthrax4.gif • http://microota.nutr.med.tokushimau.ac.jp/foodmicro/image/ • http://pathmicro.med.sc.edu/mycology/candid.jpg • www.johnes.org/.../EM_scanning-lg.jpg • www-medlib.med.utah.edu • Tortora et al, 9th edition
