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Bacteria

Bacteria. Advanced Life Science Rainier Jr / Sr High School Mr. Taylor. Characteristics. 1. All bacteria are prokaryotes (they have no nucleus or membrane-bound organelles) 2. DNA is in one single LOOP floating in the cytoplasm.

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Bacteria

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  1. Bacteria Advanced Life Science Rainier Jr/Sr High School Mr. Taylor

  2. Characteristics 1. All bacteria are prokaryotes (they have no nucleus or membrane-bound organelles) 2. DNA is in one single LOOP floating in the cytoplasm. 3. Cell wall is made of organic acids and sugars, not cellulose (“wood”). Some bacteria also have a slimy capsule.

  3. Characteristics 4. Bacteria reproduce using binary fission. 5. Some bacteria have extensions from their cell membranes; a. long whip-like appendages called flagella, often used for movement, b. shorter hair-like extensions called pili used to stick to surfaces.

  4. Shapes • Bacilli: rod-shaped bacteria. Will occur singly or in threads. E. coli is a bacillus • Spirillum: corkscrew-shaped bacteria. Tend to move by spinning. Leptospirosis species are spiral. • Coccus: round bacteria. • Diplococci: occur as pairs • Streptococci: occur in chains (Strep throat) • Staphylococci: occur in clusters (skin infections)

  5. Reproduction • Bacteria usually reproduce by binary fission. • Under certain conditions, some bacteria will form endospores: DNA is enclosed in a tough outer covering to survive the “unhealthy” conditions. • Conjugation: an exchange of DNA between two bacteria. This “plasmid” exchange is the basis of spreading antibiotic resistance among bacterial species.

  6. Energy sources • Autotrophic bacteria • Some carry out photosynthesis. • A major supplier of oxygen for our atmosphere. • Some can photosynthesize without using water, breaking down sulfur compounds instead and do not add oxygen to our atmosphere. • Chemoautotrophs • These bacteria break down molecules such as NH3, H2S, or CH4 to obtain energy • Are very important in soil chemistry

  7. Energy Sources • Heterotrophic bacteria • Are the principal decomposers in the environment. Nutrients are returned to be reused. • Some are used in the food industry (yogurt and other fermented dairy products). • Some cause disease by • metabolizing their host (tuberculosis, tooth decay) • secreting toxins that poison the host (food poisoning, E. coli infections)

  8. Symbiotic relationships • Parasite-host • Most pathogenic (disease-causing) bacteria in this category • Mutualism • Nitrogen-fixing bacteria in the roots of some plants (legumes: peanuts, soybeans, peas) • Bacteria in the digestive tract break down otherwise indigestible materials • Commensalism • Decomposers

  9. Respiration • Obligate aerobic bacteria live in the presence of oxygen • Obligate anaerobic bacteria live where no oxygen is present (or in very low levels); around thermal vents, soil, sealed areas • Facultative anaerobes: prefer areas with oxygen, can live in areas without oxygen.

  10. Bacteria Lab • Agar: furnishes the bacteria water, food, and a place to live. • Incubator: furnishes proper temperature • I have it set at 100°F (38°C) • What is the possible problem at that temperature? (If set at 86/30 it is safer!)

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