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historical periods of Microbiology, bacterial call structure, methods of microscopy
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GENERAL MICROBIOLOGY AND VIROLOGY. The morphology of bacteria and viruses. Lecture number 1. Prepared by Abdramanova Аigerym-Senior teacher, Department of Microbiology, Virology and Immunology, JSC SKMA
The subject of microbiology is the special world of living beings invisible by naked eye which sizes are within the range from 1-10 nm up to 0.1-1 mm.
Microbiology Microbiology (Greek micros - small, Latin bios - life) is a complex of biological sciences that study morphology, systematics, physiology, genetics, ecology of microorganisms, relationships with other organisms inhabiting our planet.
Microorganisms are the most ancient form of organizing life on Earth, they appeared long before the appearance of plants and animals - about 3-4 billion years ago. At present, microorganisms represent the most significant and most diverse part of organisms inhabiting the biosphere of the Earth. This served as the basis for the separation of all microorganisms into 4 large kingdoms: bacteria, fungi, protozoa and viruses. Each of them is an object of study of separate sections of microbiology, independent disciplines - bacteriology, virology, mycology, protozoology
The tasks of microbiology and immunology: • to give an idea of the classification and biological properties of pathogenic and conditionally pathogenic microorganisms; • to acquaint with modern methods of microbiological diagnosis of common infectious and non-infectious diseases of microbial etiology and to give an idea of the structure of the immune.
Taking into account the tremendous role the microorganisms play in nature, the problems of microbiology are rather diverse. Microbiology steadily differentiates into various scientific parts and disciplines. Modern microbiology includes general microbiology (investigates common principles of structural organization and general functions of microorganisms), special microbiology (performs the detailed study of certain microbial agents and groups); industrial microbiology that is the major part of modern biotechnology; agricultural microbiology; space microbiology; sanitary microbiology; veterinary microbiology; and medical microbiology.
The main goals of medical microbiology: • 1. Laboratory diagnosis of diseases caused by microorganisms by means of versatile microbiological methods; the detection of pathogenic microbial agents in living organisms and external environment. • 2. Sanitary control of microbial pollution of water, air, soil, house, foodstuffs, drugs, etc. • 3. The development of biological products for medicine (antibiotics, vaccines, immune sera, polyclonal and monoclonal antibodies, cytokines and others) that are used for prophylaxis and treatment of bacterial, viral, fungal and protozoan diseases; autoimmune and inflammatory disorders.
HISTORY OF MICROBIOLOGY: DESCRIPTIVE PERIOD The end of XVII – middle of XIX century: • Discovery of the world of microorganisms, description of microorganisms. • Anthony van Leeuwenhoek – discoverer of first microorganisms
PHYSIOLOGICAL (PASTEUR’S) PERIOD Middle of XIX – beginning of ХХ century: • Study of living activity of microbial cell, discovery of infectious (causing disease) bacteria, beginning of scientific microbiology. Louis Pasteur Robert Koch
SCIENTIFIC CONTRIBUTION OF PASTEUR • Discovery of pathogenic microorganisms – Staphylococcus – Pneumococcus – Clostridium • Development of active (live weakened) vaccines - chicken cholera – anthrax – rabies • Other discoveries – microbial nature of fermentation – microbial nature of “disease” of wine and beer – impossibility of spontaneous self-origin of microorganisms – methods of dry heat sterilization and pasteurization
SCIENTIFIC CONTRIBUTION OF KOCH • Discovery of pathogenic microorganisms – anthrax rod – cholera vibrio (Koch’s comma) – tuberculosis rod (Koch’s rod) • Development of basic principals of identification of pathogenic microbes causing disease – Henle-Koch postulates: 1. Microbe has to be isolated from individuals suffering from the disease 2. The etiological agent (microbe) must be cultivated in pure culture 3. Pure culture of the pathogen when introduce into susceptible host (experimental animal) has to produce the symptoms characteristic for the disease • Other discoveries – solid agar media for cultivation of microorganisms – aniline dyes – immersion objective for light microscopy – microphotography – sterilization by steam
IMMUNOLOGICAL PERIOD Beginning – middle of ХХ century • Discovery of immune response Metchnikoff Ehrlich
Ehrlich – founder of humoral theory of immunity – developer of chemotherapy of infectious diseases
MODERN PERIOD Middle of XX century Molecular biological methods of research
Principles of Microbial Classification The science that studies classification is called taxonomy. It includes three interrelated areas:
By the decision of the International Code for Bacteria the following taxonomic categories are recommended: class, department, order, family, genus, species. The name of the species corresponds to a binary nomenclature, i.e. consists of two words. For example, the causative agent of typhoid fever is written as Salmonella ryphi.
According to the classification D. Burgey are divided into 4 departments Gracilicutes- bacteria with a thin cell wall, gram-negative; Firmicutes- bacteria with a thick cell wall, Gram-positive; Tenericutes- bacteria "soft", "tender" without a rigid cell wall, including mycoplasmas; Mendosicutes- the so-called arhebacteria, characterized by a defective cell wall.
Morphology of Bacteria Bacteria (Gk. bakterion – small stick) are predominantly unicellular organisms. The size of bacteria varies from 0.1 to 20 mm or more. Most of pathogenic bacteria are within the range 0.2 to 10 mm. The shapes and sizes of microbes are not strictly stable. They get adaptation to the surroundings and environmental conditions. But in constant situations bacteria maintain their sizes and shapes that are specific characteristics for certain microbial groups.
The structure of bacteria is well studied by electron microscopy of whole cells and their ultra-thin sections. A bacterial cell consists of a cell wall, a cytoplasmic membrane, a cytoplasm with inclusions, and a nucleus called a nucleoid. There are additional structures: capsule, microcapsule, mucus, flagella, saw, some bacteria under adverse conditions are able to form spores. The composition of bacteria, like other microbes, includes water, proteins, nucleic acids, carbohydrates, lipids, mineral substances.
Bacterial cells can be classified into Gram-positive orGram-negative based on the structural differences betweenGram-positive and Gram-negative cell walls. The cell walls ofthe Gram-positive bacteria have simpler chemical structurescompared to Gram-negative bacteria.
