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Transcript
Chapter 23 Bacteria Prokaryotes are single celled organisms that do not have a membrane bound nucleus. Domain Archaea o They differ from bacteria in the make up of their cell walls, membrane lipids, genetics, and metabolism. o Archaea were first discovered in extreme environments such as swamps, salt lakes, and hot springs. Archaeal Groups o Methanogens They convert hydrogen gas and carbon dioxide into methane gas for energy Oxygen is poisonous to them so the are anaerobic and found in deep fresh water, marine mud, swamp mud, and sewage They are found living in the stomachs of cows and termites o Halophiles Are found in very high salt concentrations such as The Great Salt Lake and The Dead Sea o Thermoacidophiles Live in very acidic environments that have very high temperatures such as hot springs They can also be found on the ground near volcanic vents and in the oceans near hydrothermal vents called black smokers Domain Bacteria o Most known prokaryotes are bacteria. They occur in many shapes and sizes. Bacilli are rod shapes bacteria Cocci are sphere shaped bacteria Spirilla are spiral shaped bacteria Streptococci are chains of cocci Staphylococci are grapelike clusters of cocci Important bacterial groups o Proteobacteria are both aerobic and anaerobic Rhizobium are nitrogen fixing bacteria and are found in the roots of legumes, which include peas, beans, alfalfa, and clover. They fix atmospheric nitrogen into ammonia which plants can use. Some species of proteobacteria are enteric, they live in human and animal intestines. E.coli makes vitamin K and help digestive enzymes with breakdown of food. Some E. coli and species of Salmonella can cause foodborne illnesses o Gram Positive Bacteria Streptococcus bacteria causes strep throat Clostridium botulinum causes botulism, they release toxins into the environment Lactobacilli turns milk sour and makes yogurt Bacillus anthracis makes the biological weapon anthrax Actinmyocetes are a form of bacteria that make antibiotics o Cyanobacteria make their own food through photosynthesis but are not plants. They lack a nucleus and membrane bound organelles. They are believed to be the first oxygen producing organism on Earth and responsible for putting oxygen into our atmosphere o Spirochetes are responsible for the STI syphilis and for Lyme disease o Chlamydia another STI Biology of Prokaryotes o Structure and Function Cell Wall is made of peptidoglycan instead of cellulose Cell membrane regulates what enters and leaves the cell The cell membranes of photosynthetic bacteria contain thylakoids which contain pigments DNA is a single closed loop attached at one point to the cell membrane, it is not enclosed in a nucleus Capsule is an outer covering of polysaccharides that bind to the cell wall protecting it from dry harsh conditions Pili are short hair like projections on the surface of a bacterium that allow it to attach to other bacteria and to host cells Endospores can form in some bacteria that are in unfavorable conditions. They surround and protect the DNA until conditions are right. They can stay in this state for years. Flagella are long hair like projections that help the bacterium move. They whip back and forth. Movement is called taxis. Some bacteria release a slime layer and move through it. Pathology is the scientific study of disease. Bacteria and other organisms that cause disease are called pathogens. Some bacteria cause disease by making certain poisons called toxins. o Exotoxins - Toxic substances that bacteria secrete into their environment. Example: Tetanus is caused by the bacteria Clostridium tetani o Endotoxins- Toxic substances that are not released until the cell dies. They can cause fever, body aches, diarrhea, hemorrhage, and weakness. Antibiotics affect bacteria by interfering with certain cellular activity. o Penicillin blocks the ability to build new cell walls o Tetracycline blocks protein synthesis Antibiotics are made naturally by some fungi and bacteria. Antibiotic resistance is a major problem. Mutations have allowed bacteria to become resistant to some antibiotics. Some bacteria now have resistance genes that protect the bacteria from antibiotics.