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Bacteria II Notes

Learn about the typical morphology of bacteria and the important functions of the plasma membrane, cell wall, cytoplasm, and ribosomes. Explore topics such as movement, respiration, and nutrition in bacteria.

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Bacteria II Notes

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  1. Bacteria II Notes cont’d

  2. Recap: Typical Bacterial Morphology • Plasma Membrane • DNA Molecule • Cell Wall • Cytoplasm • Ribosomes

  3. Important function is to prevent cell from swelling with water until it bursts Outside plasma membrane Gives cell shape & rigidity along with supporting & protecting the bacteria Contains peptidoglycan layer (not cellulose like plants) – only found in bacteria Bacterial MorphologyCell Wall

  4. Bacterial MorphologyCell Wall • Bacteria can be divided on the basis of staining properties of the cell wall • Gram positive – stains purple. Cell walls have a single layer of peptidoglycan • Gram negative – stains pink or red. Two layered cell wall. A thin inner layer of peptidoglycan, and an outer layer of phospholipids, glycolipids & proteins • Outer layer is less vulnerable to a person’s immune system • Penicillin acts by blocking peptidoglycan synthesis • Not all bacteria have cell walls

  5. Bacterial MorphologyPlasma Membrane • Located next to the cell wall on the inside • Because bacteria lack mitochondria and chloroplasts, enzymes and electron carriers involved in respiration & photosynthesis are located here.

  6. Covers the whole bacteria. Protects bacteria against phagocytosis of host white blood cells Bacterial MorphologyCapsule

  7. Endospores are the most resistant living structures known. Helps bacteria survive heating, drying and freezing conditions. Thick wall of several layers containing DNA, ribosomes & other cytoplasmic constituents inside the cell. Can survive several hours boiling & may remain viable for years Produced by Gram+ bacteria Exposure to proper stimuli (food, warmth & moisture) the spore germinates and a new vegetative cell emerges. Bacterial MorphologyEndospores

  8. Jelly like solution is the Cytosol It contains: Macromolecules Proteins RNA Amino acids Glucose Fatty acids Nucleotides Approx 50,000 ions Bacterial MorphologyCytoplasm

  9. Scattered free in cytoplasm Antibiotics like erythromycin, streptomycin, tetracycline & choloramphenicol destroy bacteria by inhibiting ribosomes from making proteins w/o hurting or inhibiting eukaryotic cells Bacterial MorphologyRibosomes

  10. No True Nucleus Single, circular strand of only DNA that carries genes for all but a few of its proteins It is packed together in a discrete part of the bacterial cytoplasm called the nucleiod. Attached at one point to the plasma membrane. May also be tiny loops of DNA called plasmids that can travel from one bacterium to the next. They carry genes for 2 or 3 proteins – often are resistant to antibiotics Bacterial MorphologyNucleic Acid (DNA)

  11. Movement • Not all bacteria are capable of movement • Non-Motile – those that do not move • Motile – those that do move • Some bacteria move by gliding over a layer of slime • Spirochete bacteria move by twisting or turning like a corkscrew through water or other liquids. • Others propel themselves by using flagella

  12. Whip like structure extended from the cell wall – used to propel the cell Bacterial MorphologyFlagella

  13. Chemoreceptors in the cell membrane that direct bacterial movement towards nutrients or away from harmful chemicals Bacterial MorphologyChemotaxis

  14. Short slender tubes formed of protein subunits that extend from the cell wall Other pili – help bacteria adhere to objects like O2 and food Sex pilus – involved in conjugation Bacterial MorphologyPilus (Pili)

  15. Bacterial RespirationAerobic Bacteria • Most bacteria are aerobic (they need oxygen) • Obligate aerobes live where there is ample oxygen • Facultative anaerobes do not require oxygen but grow better when it is present

  16. Bacterial RespirationAnaerobic Bacteria • Under anaerobic conditions, the bacterium switches to the process of fermentation for its source of energy (it oxidizes sugar to pyruvate and produces ATP) • Obligate anaerobes grow only under anaerobic conditions and can be killed by oxygen. • Botulism, tetanus & other serious diseases

  17. Bacterial Nutrition • Photosynthetic Autotrophs • They obtain their energy from the light. • This photosynthesis uses different pigments than plants do • Some bacteria don’t use water or produce oxygen, they use carbon dioxide and produce sulfur

  18. Bacterial Nutrition • The Heterotrophs • Are found everywhere • Need organic molecules as energy source, but are not adapted to trapping food containing these molecules. • Some are parasites – absorbing nutrients from other living organisms. • Others are saprobes – feeding on dead organisms or organic wastes. Called recyclers.

  19. Bacterial Nutrition • Chemosynthetic Autotrophs • They obtain their energy from the chemosynthetic breakdown of inorganic substances. • Some can break down sulfur and nitrogen compounds. • Can convert nitrogen in atmosphere to forms used by plants.

  20. Bacterial ReproductionSexual or Asexual Reproduction *When the bacterium reaches a certain size, it divides.

  21. Bacterial ReproductionAsexual Reproduction Sometime prokaryotes divide by Binary Fission (Asexual Reproduction). • Binary Fission results in 2 identical bacteria through normal cell division. • The DNA molecule replicates itself and the DNA molecules become attached, side by side, to the inner surface of the plasma membrane. • The membrane elongates separating the 2 molecules.

  22. Binary Fission cont. • The plasma membrane pinches inward to form a central transverse septum. • The cell wall grows inward within septum & the cell divides. • Each cell receives one of the DNA molecules and about half of the cellular material. • Bacteria carry out Binary Fission at very rapid rates.

  23. Bacterial Reproduction Sexual Reproduction (DNA Variability) Many times, bacteria can exchange genetic material before dividing by Binary Fission. Because two different bacteria unite to exchange genetic information, it is said to be Sexual Reproduction. • Sexual Reprod. Types (DNA Variability) • Conjugation • Transformation • Transduction

  24. Bacterial Reproduction DNA Variability Conjugation(Direct cell to cell contact) Sex Pilus • F Factor codes for the sex pilus • Cells lacking F Factor can only receive DNA during conjugation and is called F- • Cells possessing F+ Factor have a sex pilus & can donate DNA • F+ cell contacts the F- cell using its sex pilus & a conjugation bridge is formed • A copy of its DNA is transferred from the F+ to the F- cell. (F- eventually being changed into F+)

  25. Conjugation Cont. • The conjugation bridge (F+ to F-)can be used to transfer either a plasmid or a portion of the bacterial chromosome. • A plasmid is an extra chromosomal circular DNA segment that can reproduce independently of the bacterial chromosome.

  26. Bacterial Reproduction DNA Variability • Transformation • When a bacterium dies, fragments of its DNA may be released intact • If this fragment contacts a competent member, it can be bound to the cell and taken inside (not all bacteria can do this) • After it’s been taken up, part of it is incorporated into the genome (DNA) of the recipient

  27. Bacterial Reproduction DNA Variability • Transduction (Virus-mediated transfer) • Transfer of genetic material from one bacterium to another by a virus

  28. Preventing Invasions • First line of defense against disease microbes is your body surface (Skin & linings of tubes that lead to exterior) • In addition, epithelial tissues (line the body and cavities) secrete materials that kill microbes on the body surface • Salts in sweat and tears draw H2Oout of microbes, shrinking & killing the ones that live on your skin and in your eyes • Acids in stomach & vagina burn microbes

  29. Preventing Invasions • Enzyme (lysozyme) in sweat, tears, saliva, earwax & nasal secretions ruptures bacteria by digesting cell walls • Mucus & cilia trap microbes & push them to the exterior

  30. If microbes have penetrated the body….. Three lines of defense • Macrophages within vessels, searching and devouring microbes • Inflammatory response within the lymph nodes • Fever – elevated body temp. helps fight microbes by enhancing the effect of interferons, accelerating the reproduction of T cells & removing minerals from the body so that bacteria cannot use them as nutrients

  31. Cyanobacteria(Reproduction) • Their growth depends on the chemical content of the water • Dumping phosphates and other chemicals into lake water can result in rapid growth of cyanobacteria • The decay of overabundant organisms reduces the amount of oxygen in the water. This can cause fish to die and contaminates the water • Because of this, detergents are being made without phosphates

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