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The Bacteria

The Bacteria. The Bacteria. Cells are prokaryotic and amongst the smallest known cells ( length 0.5-20 µm ). No membrane bound nucleus. Have ribosomes,but no other organelles. DNA present as a long circular molecule. ( see handout for bacterial structure). Habitat.

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The Bacteria

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  1. The Bacteria

  2. The Bacteria • Cells are prokaryotic and amongst the smallest known cells ( length 0.5-20 µm ). • No membrane bound nucleus. • Have ribosomes,but no other organelles. • DNA present as a long circular molecule. • ( see handout for bacterial structure)

  3. Habitat • Bacteria are found everywhere. • Air • Water • Soil • On plants and animals. • In plants and animals.

  4. Types of Bacteria • There are three major groups of bacteria based on their shapes; coccus, bacillus, and spirillum.

  5. 1. Coccus • Plural is cocci. • Spherical bacterium • Single cells - monococci • Pairs - diplococci • Chains - streptococci

  6. 2.Bacillus • Plural is bacilli. • A rod - shaped bacterium. • Exists as single cells, in pairs (diplobacilli), and in chains (streptobacilli).

  7. 3. Spirillum • Plural is spirilli. • A spiral - shaped bacterium. • Exist only as single cells.

  8. Bacterial Structure • Cell Wall - outermost structure of the cell. • Made up of a substance called peptidoglycan ( a long chain of sugars linked to amino acids ). • Penicillin destroys bacteria by interfering with the peptidoglycan molecules.

  9. Bacterial Structure Continued • Cell Membrane - Found beneath the cell wall. • May be folded inward. • ATP production (energy), takes place on the folds of the membrane.

  10. Bacterial Structure Continued • Capsule: This is a layer of slime secreted over the cell wall of the bacterium. • The capsule provides protection for the bacterium. • Bacteria that have capsules are said to be encapsulated. • Most pathogenic bacteria are encapsulated.

  11. Bacterial Structure Continued • Flagella - Some bacteria in the bacilli and spirilli categories can move by way of flagella ( whip - like structures that propel the bacteria). • Note: Cocci do not have flagella.

  12. Bacterial Physiology-Nutritional Needs • Like all living things bacteria need food. • Bacteria are placed in one of two categories, depending on how they get their food. • The two categories are: Heterotrophic bacteria and Autotrophic bacteria.

  13. Heterotrophic Bacteria • Heterotrophs must get their food from a source of pre-formed organic matter: • (A) Saprobes- feed on the remains of dead plants and animals. • (B) Parasites - live on or in the organism and cause disease. For example, Mycobacterium tuberculosis.

  14. Autotrophic Bacteria • Autotrophs can make their own food: • Photosynthetic-use a special type of chlorophyll called bacteriochlorophyll. • O2 is not released in bacterial photosynthesis • Chemosynthetic -obtain energy by breaking down inorganic material such as iron or sulfur.

  15. Bacterial Physiology-Reproduction • The growth of bacteria is limited by the following factors: • temperature • pH • moisture content • nutrient availability • competition from other organisms

  16. Bacterial Physiology-Reproduction continued • Bacteria reproduce asexually by binary fission. Using this process bacteria reproduce about every 20 minutes.

  17. Bacterial Physiology-Reproduction continued • The rate of reproduction can be plotted in a graph called a Growth Curve. • Under ideal conditions one bacterial cell can produce a mass of 2 million Kg in 24 hours. • In reality this never happens. Why?

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