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Viruses & Bacteria

Viruses & Bacteria. Chapter 19 Pages 471 - 490. Compare/Contrast. Prokaryotes (Bacteria) Eukaryotes Smaller Larger Simpler Complex Has genetic material Has genetic material No nucleus Nucleus Grow, reproduce, & Grow, reproduce, &

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Viruses & Bacteria

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  1. Viruses & Bacteria Chapter 19 Pages 471 - 490

  2. Compare/Contrast Prokaryotes (Bacteria)Eukaryotes Smaller Larger Simpler Complex Has genetic material Has genetic material No nucleus Nucleus Grow, reproduce, & Grow, reproduce, & respond to environment respond to environment Some move by gliding All move or swimming Some have internal Have internal membranes membranes Unicellular Unicellular & multicellular Has organelles & cytoplasm

  3. Bacteria • Prokaryotes • Smallest, most common microorganism • Single-celled • Lack nucleus • Has DNA

  4. Bacteria • 2 Kingdoms • Archaebacteria • Look similar. • Live in harsh environments. • Lack peptidoglycan in the cell wall. • Have different membrane lipids. • DNA sequences of key genes are more like those of eukaryotes than eubacteria. • Are thought to be ancestors of eukaryotes. • Ex. Methangones- produce methane gas.

  5. Bacteria • 2 Kingdoms • Eubacteria (pg. 472) • live almost everywhere, larger of the two. • Usually surrounded by a cell wall made up of carbohydrate & peptidoglycan. • Cell membrane inside cell wall. • Cytoplasm. • Ex. E coli

  6. Bacteria • How we Identify Prokaryotes (cont.): • How they release energy by cellular respiration and fermentation • Obligate aerobes – require constant supply of oxygen. Ex. Tuberculosis. • Obligate anaerobes – do not require oxygen. Oxygen could kill it. Ex. Botulism is found in canned food that’s not properly sterilized. • Facultative anaerobes – can survive with or without oxygen. Can live anywhere. Ex. E coli which is found in the large intestines or in sewage or contaminated water.

  7. Bacteria contain: • one circular piece of DNA • tiny circular pieces of DNA called plasmids • ribosomes

  8. Bacteria have cell walls made of: • peptidoglycan (a sugar linked to chains of amino acids). • this may be covered with an outer membrane of lipopolysaccharide (chain of sugar with a fat attached).

  9. Some bacteria: • have a gelatinous layer called a capsule surrounding the cell wall. • form thick-walled endospores around chromosomes when they are exposed to harsh conditions (drought, high temperatures) - these types cause botulism

  10. Some bacteria have: • flagella for locomotion. • pili(short, thicker outgrowths that help cell to attach to surfaces)

  11. Rod shaped are called bacillus • Sphere shaped are called coccus • Spiral shaped are called spirillum

  12. Bacteria • How we Identify Prokaryotes: • Shape – bacilli, cocci, spirilla. • By the way they move. • By the way they obtain energy. • Most are Heterotrophes which obtain energy by consuming food. • Chemoheterotroph- Ex. Botulism (food poisoning). • Photoheterotroph- uses photosynthesis. • Autotrophs make their own food. • Chemoautotroph- found in deep ocean floors. • Photoautotroph- found near surface in lakes oceans & streams. • The chemical nature of their cell walls. • A method of Gram Staining is used to determine nature. Gram (+) = violet, Gram (-) = pink.

  13. Bacteria • Reproduction • Binary fission – DNA replicates & divides producing 2 daughter cells. Asexual reproduction. • Conjugation – process where genetic information is exchanged. • Spore formation – an endospore may form when growth conditions become unfavorable.

  14. Bacteria reproduce: asexually using binary fission.

  15. Bacteria reproduce: sexually using conjugation. Bacteria exchange plasmid DNA. This is how bacteria become antibiotic resistant.

  16. Most are heterotrophs: • Decomposers – feed on and recycle organic material • Pathogens – parasitic, disease-causing bacteria • Either attack cells or secrete toxins • Nitrogen-fixing bacteria(Rhizobium) • Found in nodules of soybeans, peanuts, alfalfa, and clover • Convert atmospheric nitrogen (N2) into ammonia, called nitrogen fixation. • Used in crop rotation

  17. Nitrogen fixing bacteria in the nodules of roots

  18. 2. Some are photosynthetic. • These are autotrophs that use the sun’s energy to make food.

  19. 3. Chemoautotrophs • Obtain energy from molecules like ammonia and methane to make food. • Examples: Nitrobacter and Nitrosomonas • - live in soil • - have a crucial role in nitrification (turn ammonia into nitrates, the form of nitrogen commonly used by plants).

  20. There are three types of bacteria based on how they obtain energy: heterotrophs, photosynthetic, and chemoautotrophs. This is the anthrax bacterium.

  21. Antibiotics: • work by preventing cell wall formation, breaking up cell membranes, or disrupting chemical processes. • cannot treat viral infections.

  22. Strep throat Streptococcus Staphylococcus

  23. Gonorrhea-Passed from Mother to Baby

  24. Syphilis

  25. Helpful Bacteria • Decomposers break down dead organic material • Biotechnology - inserting helpful genes into a plasmid • Bioremediation - bacteria eat up oil spills • Food production – cheese and yogurt • Put nitrogen back into the soil • Aid in digestion

  26. Interdependence Viruses and organisms relyon their environmentand other species for survival.

  27. Viruses • Viruses are NOT cells. A virus is an infectious agent made up of: • a core of nucleic acid (RNA or DNA) • a protein coat

  28. Alive or not? Even scientists disagree as to whether or not viruses are alive. What do you think? Look at the chart on the next page to help you decide.

  29. Characteristic of life

  30. Viruses • Viruses are particles of: • Nucleic acid • Protein • Lipids (only in some) • They vary in size and structure. • They enter living cels & use the machinery of the infected cell to produce more viruses. • Composed of: • A core DNA or RNA (which has the instructions for making copies) • This is surrounded by a protein coat called a capsid which binds the virus to the surface of the host cell.

  31. Structureof a virus • Envelope (part of the protein coat) • Capsid (part of the protein coat) • Nucleic acid (either DNA or RNA) ENVELOPE NUCLEIC ACID CAPSID

  32. Viruses • Bacteriophages- • Viruses that infect bacteria. • Ex. Bacteriophage T4

  33. Bacteriophage • A virus that only infects bacteria CAPSID HEAD DNA CAPSID TAIL FIBER

  34. Ticking time bombs . . . Viruses do not reproduce, EXCEPT inside a living cell. They invade a living cell and let the cell do the work for them.

  35. Lytic Cycle The viral infection that rapidly kills the host cell is the lyticcycle.

  36. Cycle Illustration 1 2 3 4 5

  37. Lysogenic Cycle The viral infection that enters a cell, remains harmless for a period of time (sometimes years), and then becomes harmful later is called the lysogenic cycle.

  38. Viruses • Once inside a host cell: pg. 481 • Lytic infection • Virus inters cell and makes copies of itself. • Causes cell to burst, releasing new virus particales that can attack other cells. • It then uses materials of host cell to make copies of its own DNA molecule. • Host cell is destroyed. • Lysogenic infection • Virus integrates its DNA into the DNA of host cell. • The viral genetic info. replicates along with the host cell’s DNA. • Viral DNA that’s embedded in host’s DNA is called prophage. • Unlike lytic, it does not lyse the host cell right away so it may remain a part of DNA of host for many generations.

  39. Viruses Retroviruses • contain RNA as their genetic information. • Genetic information is copied backwards. • It may remain dormant for any length of time before becomes active and it can cause death of the host cell. • Ex. AIDS, some cancers.

  40. Retrovirus • A virus that contains RNA instead of DNA • Human Immunodeficiency Virus (HIV) is a retrovirus • HIV causes AIDS CAPSID ENVELOPE RNA

  41. Viruses • Must infect living cells in order to reproduce. • Are Parasites. • Are not considered to be living things because they are not made up of cells & cannot live independently. • See Chart on pg. 483

  42. Obj. 15 – Jenner and Pasteur (p. 931) • Edward Jenner, English Doctor…. • Invented vaccine • Infected own son with cow pox (a mild form of small pox) • Son didn’t contract small pox • Cow pox triggered immune system to create an immunity against small pox

  43. Obj. 15, cont. • Louis Pasteur • Pasteurization • Disproved spontaneous generation • Said “life came from life” • Boiled broth to kill microorganisms

  44. Obj. 16 – What is an epidemiologist? (p. 457) • A scientist who studies the causes and controls of disease outbreaks. • Involved in preventing disease outbreaks and in stopping outbreaks that do occur spreading. • Work for CDC, FBI, etc.

  45. Obj. 17 – Inoculation & Incubation of culture medium • Culture medium – either a broth or an agar with nutrients added to it to aid in the growth of microorganisms. • Inoculation – referred to as a streak or stab (putting microorganisms in a nutrient agar or broth so they can grow) • Incubation – usually 24 – 48 hours at a temperature of 20º C or 37º C.

  46. Inoculation Technique Heat loop Inoculation

  47. Inoculation Broth Inoculation Slant

  48. Agar Plate Agar Deep

  49. Streak Plates

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