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Prokaryotes • • • • • • • • • General information General structures/functions Reproduction (binary fission) Genetic recombination mechanisms: conjugation, transformation, transduction Endospore production Modes of nutrition: aerobic vs. anaerobic & autotrophs vs. heterotrophs Free-living vs. symbiotic types of bacteria Diseases & treatment DOMAIN Bacteria – Bacteria – Cyanobacteria • DOMAIN Archaea - methanogens, halophiles, thermoacidophiles Prokaryotes • Prokaryote – lack nucleus and various organelles (do have ribosomes) – Oldest and most simplest forms of life • Two Domains (molecular/cellular differences): Bacteria & Archaea • Previously placed in Kingdom Monera • Widely distributed in nature: – Soil, water, air, etc. • Most abundant of any organism – 1 gram of soil = 100 million bacteria cells • Tiny, unicellular organisms: 1 µ m to 10 µ m (1 µ m = 1/1,000,000 m) • Structures associated with bacteria – Nucleiod - contains single circular strand of DNA – Plasmid - accessory ring of DNA (used by scientist for Cytoplasm genetic engineering) – Ribosomes - responsible for protein synthesis – Plasma Membrane - acts as a barrier between the internal and external environment Cell – Cell Wall - surrounds plasma membrane (composed of Envelope peptidoglycan) – Capsule/Slime Layer - surrounds cell wall; protective – Pili - short hair-like structures for adhesion to surfaces Appendages – Flagellum - whip-like projection; gives cell motility • Reproduction - asexual thru Binary Fission – Daughter cells genetically identical to parent Parent Daughter Cells Genetically the same as the original parent cell • DNA variations occur via genetic recombination (NOT binary fission) – Transformation - incorporates DNA from the environment into genome – Conjugation - transfer of genetic information from one cell to another via “sex” pili – Transduction - bacteriophages transfer bacterial DNA from one cell to another Ways that bacteria can develop antibiotic resistance Transformation Transduction • Endospores are formed by some bacteria when exposed to hostile environment Some hardy for years! – Purpose: survival – not reproduction – When conditions become “friendly” again the cell become active • Anthrax & Botulism are conditions resulting from organisms that generate endospores; Toxins release produce symptoms of these diseases. • Means of Nutrition • Environmental conditions required for metabolism (cellular respiration) to occur vary – Obligate anaerobes - survives only when free oxygen NOT present – Facultative anaerobes - grows either in presence or absence of free oxygen – Aerobes - requires free oxygen to be present • Modes of nutrition also vary – Autotrophs • photosynthesizers = cyanobacteria • chemosynthesizers = archaeabacteria – Heterotrophs = most bacteria • MOST are free-living heterotrophs • Ecological (Environmental) Importance: – Saprotrophs/decomposers – live off dead organic material – Important in recycling nutrients in ecosystems. • Economic Importance: – Used to make: alcohols, acetic acid, acetones, antibiotics – Used to make food: cheeses, butter, sauerkraut • SOME develop symbiotic relationships 1.Mutualism - both bacteria and host benefit (e.g. nitrogen-fixing bacteria in roots) 2.Commensalism - bacteria benefits and other is not harmed nor benefits 3. Parasitism - bacteria causes harm to host (e.g. causes diseases aka “pathogens”) • Examples of diseases: – – – – – – – STDs – syphilis, gonorrhea Respiratory Disease – strep throat, scarlet fever, tuberculosis Skin Disease – boils, pimples Digestive tract disease – food poisoning, dysentery, cholera Nervous system disease – botulism, tetanus, leprosy Systemic disease – plague, typhoid fever Other – Lyme disease • Treatment/Prevention: – Antibiotics – inhibit cell wall synthesis or inhibit protein synthesis - targets prokaryotic cells and not eukaryotic cells – Public awareness – good food prep, handwashing – Vector control – fleas, ticks, etc • DOMAIN Bacteria • Bacteria – commonest type of prokaryote • Three Basic Shapes: – Bacillus = rod – Coccus = round – Spirillum = curved/spiral/helical Prokaryotes - Cell Wall & Gram Stain • Cell wall maintains cell integrity and composed of peptidoglycan – polysaccharides cross-linked w/ peptides (various lengths) • Archaea do not have peptidoglycan, some have pseudopeptidoglycan – pseudomurein • Composition of cell wall is basis of Gram stain – thick layer of peptidoglycan = stain positive - purple – thin layer of peptidoglycan = counter stain - red Prokaryotes - Cell Wall & Gram Stain • Gram-positive bacteria have thick peptidoglycan layer – teichoic & lipoteichoic acids embedded in wall • Gram-negative bacteria have thin peptidoglycan layer – additional outer membrane with lipopolysaccharide & porins • Cyanobacteria (old terminology blue-green algae) – May appear other colors: red, yellow, brown – Environment: aquatic or moist surfaces – Autotrophic via photosynthesis • Photosynthetic pigments found in thylakoids (NOT CHLOROPLAST) • * Thought to have released free oxygen in earth’s primitive atmosphere – May live singly, in colonies or be filamentous • Unicellar form – e.g. Gloeocapsa • Colonial form – e.g. Anabena • Filamentous form- e.g. Oscillatoria – Lack visible means of locomotion – Some have heterocysts that ‘fix’ atmospheric nitrogen (e.g. Anabaena) – First in aquatic food chain (producers) • * Thought to be first colonizers of land – Some form symbiotic relationships (e.g. with fungi = LICHENS; important to soil formation) – Associated with pond/lake “blooms” and fish kills • DOMAIN Archaea – Composition of cell wall different than in other types of bacteria – Different ribosomal RNA nucleotide base sequencing than other bacteria. – Share more similarities to Domain Eukarya than other bacterial types – Plasma membrane has high lipid content – Most are autotrophic via Chemosynthesis – These prokaryotes live in extreme environments (similar to primitive earth). • Examples of Archaeabacteria: – Methanogens - produce methane gas • GI tract of some animals, swamps, marshes – Halophiles - survive in salty environments (12 – 15% NaCl) • Great Salt lake and Dead Sea – Thermophiles - loves acid conditions & extreme heat • Hot springs, geysers, thermal vents – None known to be parasitic