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Transcript
KINGDOMS EUBACTERIA & ARCHAEBACTERIA • Bacteria are 1- celled organisms that live everywhere. They are the oldest life forms on Earth. E. coli is the most studied bacterium. All bacteria are prokaryotic meaning they have no true nucleus (they do still have genetic material). Bacteria do contain cell walls containing acids & sugars that provide support as well as a cell membrane inside of this cell wall. Some antibiotics work by attacking this structure. KINGDOM ARCHAEBACTERIA • Anaerobic & aerobic bacteria adapted to environments with extreme temps, acidity, or salt content; differ from eubacteria in structure of cell wall & cell membrane – RNA polymerase & ribosomal protein very similar to eukaryotes (believed to be more closely related to eukaryotes than eubacteria) – asexual reproduction only Examples of Archaebacteria • Thermophiles • Acidophiles • Halophiles Habitat of Archaebacteria • Extreme environments – swamps, deep seas, cow stomachs, sewage treatment, Dead Sea, volcanoes, geysers Nutrition Methods of Archaebacteria • Can be heterotrophic or chemosynthetic. Cyanobacteria are photosynthetic. KINGDOM EUBACTERIA • No membrane-bound organelles, nutrition by absorption (some are photosynthetic or chemosynthetic), reproduce by fission or budding. Bacteria come in 3 primary shapes • 1. Cocci - sphere-shaped • 2. Bacillus - rod-shaped • 3. Spirilla - corkscrew-shaped Bacteria may also be classified based on their shapes in a group • These include 1. Diplo - found in pairs • 2. Staphylo - found in clusters • 3. Strepto - found in chains • The walls of bacteria can be either rigid or flexible. Some produce a slime layer known as a capsule. This structure protects the bacterium from the immune system. Bacteria may also be classified as Gram positive or Gram negative based on their colors after a Gram stain. • Those that are Gram positive stain purple because of a thick peptidoglycan layer in the cell wall (treat these with pencillin). Those that are Gram negative stain pink because the outer membrane is removed by the alcohol rinse & the peptidoglycan layer allows the dye to leave (treat these with tetracycline). • Bacteria contain many ribosomes & plasmids that are small segments of DNA. Some bacteria may have flagella while others may have pili that resemble cilia. These allow the bacteria to attach to food. Some bacteria are motile while others cannot move. Some bacteria are heterotrophic while others make their own food & are therefore considered to be autotrophic. • Some bacteria are saprophytic which means they feed on dead organisms. Those bacteria that require oxygen to live are called obligate aerobes. An example is Tuberculosis. Those that can survive without oxygen are termed obligate anaerobes. An example is Botulism. Those that can live with or without oxygen are termed facultative anaerobes. An example is E. coli. • A colony is a large group of bacteria living together. All members are descendants of a single bacterium. • Some bacteria form endospores when conditions are harsh. The bacterium makes a membrane around itself when food or nutrients become low. The membrane wraps around one strand of DNA & some cytoplasm & becomes dormant. Reproduction of bacteria • Asexually – binary fission, budding (some can also use transformation, transduction, & conjugation) • Most bacteria can reproduce at a rate of every 20 – 30 minutes. This occurs through the process of fission usually, but may also occur through the process of conjugation. In this process a donor bacterium transfers genetic material to an acceptor bacterium through direct contact . BACTERIA IN NATURE • Bacteria help the ecosystem recycle nutrients. Because they break down materials, they are known as decomposers. They play a significant role in sewage treatment. Bacteria also are involved in Nitrogen fixation, a process where they convert atmospheric nitrogen into a form plants can eventually use. Humans also use bacteria to produce yogurt, cheese, pickles, sauerkraut.