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ORIGIN OF LIFE THE CELL ALL LIVING THINGS ON EARTH ARE CHARACTERIZED BY CELLULAR ORGANIZATION, HOMEOSTATSIS, GROWTH, HEREDITY AND OTHER LIFE FUNCTIONS. THE PROKARYOTIC CELL THE EARLIEST CELL WHAT DOES PROKARYOTIC MEAN? CELL LACKING A TRUE NUCLEUS and MEMBRANE BOUND ORGANELLES BACTERIA REFLECT THE IDEA OF A PROKARYOTIC CELL Taxonomy the Science of Classification Due to the great number and diversity of organisms, biologists use the characteristics of different organisms to describe specific forms of life and identify new ones. Classification: is the grouping of related organisms Carolus Linneaus is credited with foundings of Taxonomy – He originated the binomial nomenclature system. Ie. Genus and species Also established a hierarchy of taxonomic ranks – KPCOFGS – the highest level being the Kingdoms He established a 2 kingdom system – plant and animal Classification Since Linnaeus 1. 6 kingdom system 2. Microorganisms were identified due to tools such as the light microscope and staining techniques 3. Recently 1956- bacteria were placed in the kingdom Monera and considered Prokaryotic cells Monera (Archaebacteria and Eubacteria) Classification of Bacteria Bacteria have been classified into 33 groups 1. 2. 3. 4. Morphology: size, shape, arrangement of cells, motility, presence of cellular structures Staining: gram + and – Growth: characteristics in solids and liquids, colony morphology, pigments Nutrition: autotrophic, heterotrophic, chemotrophic (C, N, S etc) fermentative 5. 6. 7. Physiology: requirements – temp, pH, aerobic, anaerobic, salt, antibiotic sensitivity and resistance Biochemistry: cellular components, nature of the cell wall, ribosomes, reaction to biochemicals (carbs, lipids etc.) Genetics: percentage of DNA bases CLASSIFICATION OF BACTERIA Archaebacteria “ARCHAE” – ANCIENT DISCOVERED IN HARSH ANAEROBIC ENVIRONMENTS Contain unusual lipids in their cell membranes and lack peptidoglycan in the cell wall Gram + and -, motile and nonmotile, various shapes Ex. METHANOGENS, HALOPHILES & THERMOACIDOPHILES Eubacteria TODAY’S TYPICAL BACTERIA Contain a cell membrane and cell wall that contains peptidoglycan Mostly gram -, both anaerobic and aerobic, motile and nonmotile, various shapes Heterotrophic, photosynthetic and chemosynthetic Ex. Yellowstone – hot springs (hydrogen sulfide) energy source E. coli, Salmonella typhi, cyanobacteria (blue-green algae), Rhizobium, Micrococcus luteus etc. IDENTIFICATION SHAPE COMMON BACTERIA HAVE 3 SHAPES COCCI BACILLI SPIRILLA VIBRIO (comma shaped) SPIROCHETES (corkscrew) GROWTH PATTERN 3 COMMON cocci PATTERNS STAPHYLO- cluster STREPTO – chain – cocci and bacilli DIPLO – Two TETRAD - four THE BACTERIA The prokaryotic cell is a small one room compartment Components of cell 1. 2. 3. 4. 5. 6. Capsule (glycocalyx) Cell wall Cell membrane Cytoplasm DNA (chromosome) Pili (conjugation or fimbriae) 7. Ribosomes 8. Flagella 9. Inclusion (granules) energy storage of lipids 10. Plasmid Bacteria Pili: a. Fimbriae – attachment pili b. Conjugation or sex pili – attach two cells and allow the transfer of genetic material fimbriae Conjugation – attach two cells to transfer DNA Staining Techniques used to classify bacteria Based on certain cellular structures of the prokaryotic cell, stains and techniques can be used to identify a bacterium. 1. Simple Stain: adheres to the cell wall of the structure to identify morphology 2. Differential Stain: -Gram stain (cell wall characteristics) -Negative stain (capsule) 3. Special Stain: -Schaeffer-fulton spore technique (endospores) -Flagellum staining Bacteria: Negative Stain Capsule: protective, thick, slimy structure outside the cell wall -A polysaccharide substance called glycocalyx - prevents drying - prevents phagocytosis by host - serve as a binding/adhesion mechanism Produced as a defense mechanism and contributes to virulence or intensity of disease. Capsule not often visible - Negative staining allows one to view this specialized structure Negative Staining technique – Live bacteria is stained. This creates a halo affect around the cell. (Pink-red cell, capsule does not stain because of dark background. Bacteria: Gram Staining and the cell wall Most bacteria are encased by a strong cell wall PEPTIDOGLYCAN: consists of carbohydrates and polypeptide units Protect cell, maintain shape, prevent excessive water intake Some antibiotics and chemicals interfere with the production of peptidoglycan synthesis of some bacteria – destroy cell Bacteria: Gram Staining and the cell wall GRAM STAINING (CLASSIFICATION TECHNIQUE) GRAM STAINING is a staining technique that will be detected in the cell wall of some disease causing bacteria. Bacterial Smear can either be Gram + or Gram – Gram + have a thick layered cell wall will reflect a purple color Gram – do not retain the staining dye because of a lipid layer and will not retain the purple dye. Will reflect a pink color Bacteria: Schaeffer-Fulton Spore Technique Endospores 1. Specialized resting cells that survive extreme heat, toxins, radiation, disinfectants and chemicals 2. Primary function is to ensure the survival of the bacterium through times of stress 3. Extremely hard to destroy but burning and autoclaving can do this 4. Endospores can be seen with a simple stain but the SchaefferFulton Spore Technique is used to make spores more visual. (spores stain a greenish color) Schaeffer-Fulton Spore Stain - a heat fixed smear is covered with malachite green and steam heated for 10 min. The slide is then counterstained with saffranin Endospores Spores outside