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Bacteria General Characteristics Single-celled; no nucleus or complex organelles Earliest known life forms Smallest and simplest living organisms Size 20 - 200 microns in diameter and 50 – 1,000 microns long Few hundred genes Bacterial Structure All bacteria have an outer cell wall made out of glycoproteins or lipoprotein Some bacteria have a sticky envelope around the cell wall called a capsule or slime layer Very simple internal organization Cytoplasm with very few organelles Nucleoid region (loosely coiled DNA) Classification Bacteria are placed into two major kingdoms: Kingdom Archaebacteria - oldest bacteria, found in harsh environments Kingdom Eubacteria -True bacteria, the largest group. Grouped according to their shape and arrangement: Coccus (i) = Spherical shaped cells single cocci diplococci (pairs) Streptococci (chains) Staphylococci (clusters) Bacillus (i) = Rod shaped cells single bacilli Diplobacilli Streptobacilli Spirillium = spiral shaped Bacteria can also be grouped according to their living arrangements Saprophytes - live on dead things (decomposers) Symbiotes - Two organisms living and depending on each other Parasitic Commensulistic Mutualistic Bacteria Prefer: Warmth; 25-37 °C Dark Moisture Food Movement Many forms have flagella for movement Some bacteria have pili, which allow them to attach to other things Feeding and digestion Autotrophic Photosynthetic (e.g. cyanobacteria or blue-green algae) Chemosynthetic (e.g. methanogens or halophiles) Heterotrophic Extracellular digestion Secret enzymes Digest their food They absorb the food back into their cells by diffusion Circulation, Excretion and Respiration By diffusion Obligate aerobes Must have oxygen to live e.g. Mycobacterium tuberculosis Obligate anaerobes Can not live in the presence of oxygen e.g. Clostridium botulinum Facultative anaerobes Can grow with or without O2 but do better without O2 e.g. Escherichia coli Reproduction Asexual Binary fission - splitting into two equal cells Sexual reproduction Conjugation-exchange of plasmids plasmids are independent circular pieces of DNA in bacteria. after plasmid is exchanged one bacterium usually dies. Harmful Effects of Bacteria Pathogenic (cause diseases) By directly damaging cells as they digest cells for food. Or by indirectly damaging cells by releasing toxins which damage hosts. They also trigger body's immune response, i.e. fever or inflammation. Examples: botulism, tuberculosis, gonorrhea, typhoid fever, bubonic plague, diphtheria, cholera, tetanus etc. Other problems caused by bacteria Food spoilage (many species) Food poisoning Salmonella sp. Disorders like boils, pimples, pneumonia, and some forms of arthritis. Treatment of bacterial diseases Antibiotics are usually made from fungi or other bacteria. why? Examples: Penicillin, Streptomycin, tetracycline, and sulfa drugs. Problems with Antibiotics Antibiotic resistance. Kills off good bacteria as well as bad. Inhibits body's natural immunity. Pasteurization and sterilization (UV & alcohol) help prevent the spread of disease. Beneficial effects of bacteria Decomposition of organic material Nitrogen fixation in some plants (legumes) Used to make antibiotics Food production: e.g. Yogurt, Cottage cheese, Blue cheese,Vinegar Used as a tool in genetic engineering Tanning leather Curing tobacco Bioleaching-extracting minerals from ore deposits