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Download Prokaryotes Chap 18 Smallest (1-5 microns) and most
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Why study bacteria? https://www.youtube.com/watch?v=qCn92mbWxd4 Prokaryotes Chap 18 Smallest (1-5 microns) and most common living microorganism Unicellular, lack nucleus, have cell walls • Prokaryotes are widespread on the earth: only 1% have been discovered. • Two groups of prokaryotes are Bacteria Archaea About 250,000 bacteria could fit on the period at the end of a sentence. PROKARYOTES: 2 domains Bacteria •Largest group •Lives everywhere •Cell wall made of peptidoglycan Archaea • Live in extreme conditions • Cell walls lack peptidoglycans, have different lipids • Their DNA is more similar to the eukaryotes’ DNA • Different flagella structure How are they alike? • Small, single-celled, cell walls • No membrane-bound organelles, including nuclei • Circular chromosome (DNA in circle), may have plasmids (smaller circular pieces of DNA) • Move by flagella or gliding • Have pili (hairs) to stick to each other Endosymbiosis Genetic Material • DNA in a circular chromosome, may have plasmids (small circles of DNA) Movement • Flagella • Some glide in slime • Some don’t move • Have pili – small hairs for attachment archaea Bacteria Archaea’s DNA is more similar to that of the eukaryotes. eukaryotes bacteria archaea ancestor They have been around for awhile! Fossils of early cyanobacteria Bacterial shapes Bacilla - rods Coccus - spherical Spirilla- spirals Staphylococcus aureus Streptococcus bacteria Strep throat What shape? bacillus What are gram stains used for? • To identify bacteria • To select antibiotics to use for bacterial infections Cell walls and gram stains Lipids Peptidoglycan layer GRAM POSITIVE GRAM NEGATIVE Peptidoglycan is a carbohydrate in the cell walls of eubacteria. GRAM POSITIVE BACTERIA GRAM NEGATIVE BACTERIA Is this bacteria Gram-negative or Gram positive? Six common gram-positive bacteria that infect humans and their shapes follow: - Streptococcus (cocci) -Staphylococcus (cocci) -Bacillus - causes anthrax and gastroenteritis -Clostridium- causes botulism,tetanus -Corynebacterium causes diphtheria -Listeria (bacilli)- causes meningitis Staph infection Gram-negative bacteria that infect humans and their shapes follow: Spirochetes (spiral-shaped) - causes syphilis, lyme disease Neisseria (cocci) - causes meningococcus, gonorrhea Obtaining Energy • Photoautotrophs – photosynthesize ex-cyanobacteria • Chemoautotrophs – break down chemicals such as hydrogen sulfide, ammonia, nitrites, sulfur, or iron ex – those found in deep ocean vents or hot springs • Heterotrophs – eat other things • Photoheterotrophs – use light for energy but use food for nutrients Evidences of bacteria Banded iron formations from iron oxidizing bacteria chemoautotrophic cyanobacteria photoautotrophic • Some don’t need oxygen to live: obligate anaerobes (oxygen kills them) • These are found in marshes, lake bottoms, digestive tracts of herbivores Releasing energy • Obligate aerobes – need oxygen and carry on cellular respiration • Obligate anaerobes – do NOT need oxygen, carry on fermentation, found in marshes, lake bottoms, digestive tracts of herbivores ex – Clostridium botulinum – food poisoning; most potent poison, also botox • Facultative aerobes – can live with or without oxygen, can live anywhere Growth and reproduction • Divide asexually by binary fission as often as every 20 minutes • Reproduce sexually by forming conjugation tubes between cells bacteria 1 bacterial cell weighs 0.000000000001 g (1 x 10-12g) After 44 hours given optimum growth conditions and generation times of 20 minutes, what is the theoretical weight of bacteria produced? The weight of the earth! Some form endospores to encapsulate their DNA during harsh times; remain dormant until conditions improve About rice… • The main risk with cooked rice is from the food poisoning bacteria called Bacillus cereus. • The bacteria forms a hard outer coating called a spore. This spore protects the bacteria from heat during cooking. If the rice is then cooled slowly the spore will germinate producing more bacteria. These bacteria produce poisons or toxins. • Re-heating the rice will destroy some of the bacteria but they will leave behind their toxins which are not damaged by heat. These toxins cause illness. Beneficial Roles of Bacteria Bacteria live in animal digestive tracts – • help break down food • produce vitamins – ex vitamin K (blood clotting) in humans • They also take the place of pathogenic bacteria. Some foods are products of fermentation occurring in bacteria: yogurt, cheese, pickles, soy sauce, sauerkraut, vinegar Importances of Bacteria in the environment • • • Atmospheric Composition Cyanobacteria added oxygen to atmosphere Element Cycling recycle C, N, H, and S Nitrogen-fixation Bacteria take atmospheric nitrogen and convert it into ammonia so plants can use it and eventually animals. These bacteria are found in a symbiotic relationship with legume-type plants such as soybeans and stored in their root nodules. Root nodules in soy beans that store bacteria for nitrogen cycling Other symbiotic associations • Bioluminescence in fish • Toxins in skin of organisms These are due to bacteria in their skin. Some bacteria digest oil • Bioremediation – breaking down pollutants Bacteria can be good guys! Bacteria – BAD BOYS http://www.pbs.org/wgbh/nova/sciencenow/0303/video-extr-w-350-04.html Bacteria as Disease-causers • less than 10% are pathogenic (disease- causing) Bacteria cause disease in two ways: • Some damage tissue by breaking it down for food; exTB breaks down lung tissue • Some produce toxins; exStreptococcus in strep throat Prevention/treatment of disease • Skin – first defense • Vaccines – stimulate body to produce antibodies (proteins made to combat foreign invaders) - first person to make a bacterial vaccine was Pasteur with a vaccine for anthrax Anthrax is an infectious disease due to a type of bacteria called Bacillus anthracis. Infection in humans most often involves the skin, gastrointestinal tract, or lungs. In 2001, anthrax sent through the U.S. Postal Service infected 22 people; 7 survivors had confirmed anthrax disease. Bacteria good or bad? Can cause food poisoning. Used in cosmetic industry to remove wrinkles. • Antibiotics – compounds that block the growth and reproduction of bacteria • First one, penicillin, discovered by Alexander Fleming in 1928. • They block the formation of cell walls in bacteria or protein synthesis. Do not work against viruses! Other ways to control bacterial growth • Antiseptics: can be used on living tissues but not taken internally; Ex – hydrogen peroxide, germ-x • Disinfectants: used on surfaces but not safe to use on living tissues; Ex – bleach, counter-cleaners Testing effectiveness of antibacterial agents Somewhat effective Not effective Most effective Testing antibiotics and antibacterial agents on bacteria cultures The larger ring of no growth, the more effective the agent. Antibiotic resistance in bacteria https://www.youtube.com/watch?v=xZbcwi7SfZE Transmission of resistance genes via plasmid exchange in conjugation. What can you do? Don’t use antibiotics to treat viral infections. When treating a bacterial infection with antibiotics, take all your pills. http://www.pbs. org/wgbh/nova/ body/killermicrobe.html Dr. Collins and the Case of the Mysterious Infection Selective pressures that have led to antibiotic resistance • Increased antibiotic use in general, particularly among children • The misuse of antibacterial products - soaps, lotions, and dishwashing detergents. These agents alter the normal mix of bacteria and give antibiotic-resistant bacteria an opportunity to proliferate. • Use of antibiotics in animal husbandry and agriculture. Promotes resistance in treated animals, which can be passed on to caretakers and people who prepare or eat undercooked meat.