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Bacteria and Viruses

Bacteria and Viruses. Chapter 20. Viruses. Viruses are particles of nucleic acid (either DNA or RNA) surrounded by a protein coat (called a capsid ) Vary in size and structure Smallest in size—some can only be seen with electron microscopes Viruses are pathogens : agents that cause disease.

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Bacteria and Viruses

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  1. Bacteria and Viruses Chapter 20

  2. Viruses • Viruses are particles of nucleic acid (either DNA or RNA) surrounded by a protein coat (called a capsid) • Vary in size and structure • Smallest in size—some can only be seen with electron microscopes • Viruses are pathogens: agents that cause disease

  3. Viruses • Replicate by infecting cells and using the cell (called a host cell) to make more viruses • Not considered to be living because they do not have all the properties of life—they do NOT grow, have homeostasis, nor metabolize

  4. Viral Structure • Capsid- the protein coat of a virus that contains either RNA or DNA but NOT both • Envelope- surrounds the capsid and helps the virus enter cells • Consists of proteins, lipids, and glycoproteins • Variety of Shapes 1.Spherical 2.Helical 3.Polyhedral

  5. Viral Reproduction • Rely on living cells (host cells) for replication • Must infect a living cell before it can replicate • When a virus enters a cell it will begin one of 2 cycles: • Lytic Cycle- virus enters the cell, copies itself, and bursts the cell releasing the new viruses • Lysogenic Cycle- virus enters a cell, embeds its DNA into the cell’s DNA so that it is replicated along with the host cell, eventually this virus will become active and begin destroying the cells (the host cell is not destroyed)

  6. Examples of Lysogenic • Lytic • Epstein-Barr Syndrome and Mononucleosis • Lysogenic • Human Immunodeficiency Virus (HIV)

  7. Specificity • The virus recognizes a host cell at a specific site—often are restricted to certain kinds of cells • The virus and host cell interlock like a puzzle; a lock and key • This specificity explains why each virus can only invade certain types of cells

  8. Examples of Specificity • HIV- white blood cells • Polio- nerve cells • Adenovirus (cold virus)- adenoid tissue • Hepatitis- liver cells

  9. Retroviruses • Viruses that contain RNA as their genetic information • The genetic information is copied backwards (meaning that it is from RNA to DNA instead of DNA to RNA)

  10. Emerging Viruses • Newly recognized viruses or viruses that have reappeared or spread to new areas • Dangerous to public health • Examples: • West Nile • Avian Flue • Hantavirus

  11. Bacteria • Prokaryotic • Unicellular • Some autotrophic • Some heterotrophic • Some chemotrophic • Contain cell walls

  12. Kingdom Eubacteria Live almost everywhere Cell wall WITH peptidoglycan Some can cause disease Ex: E. coli Kingdom Archaebacteria Cell walls with NO peptidoglycan Live in harsh environments Ex: methanogens Kingdoms of Bacteria

  13. Eubacteria

  14. Archaebacteria

  15. Differ in at least 7 ways: Internal Compartmentalization Cell Size Multicellularity Chromosomes Reproduction Flagella Metabolic Diversity Prokaryotes ____Eukaryotes No Nucleus Nucleus Smaller Larger Uni Multi/Uni Singular DNA Proteins Binary Fission Mitosis Simple Complex Anaerobic/Aerobic Aerobic Prokaryotes vs. Eukaryotes

  16. Bacillus Rod Shaped Coccus Round Shaped Spirillum Spiral Shaped Strepto Chains Staphylo Clusters Examples: Streptococci Staphylococci Micrococcus luteus Spirillum volutans Bacillus Cell Shapes & Arrangements

  17. Arrangements

  18. Find each shape of bacteria:

  19. Cell Walls • 2 types of cell walls—distinguished by the Gram Stain technique • Gram Positive: appear purple under the microscope • Ex: streptococcus and staphylococcus • Gram Negative: bacteria appear red under the microscope • Ex: E. coli • Important in medicine because the two types differ in their response to antibiotics

  20. Gram Positive

  21. Gram Negative

  22. Reproduction and Growth • Binary Fission • No exchange of genetic information; therefore it is asexual reproduction • Replicates DNA and divides in half producing two identical daughter cells • Conjugation • Hollow bridge forms between two bacterial cells and genes move from one cell to another • Spore Formation • Endospore germinates

  23. Obtaining Energy • Autotrophs—make their own energy • Photoautotrophs: perform photosynthesis like plants (ex: cyanobacteria) • Heterotrophs—obtain energy from another source • Principal decomposers • Break down the bodies of dead organisms and make the nutrients available to other organisms • Chemotrophs • Obtain energy from inorganic materials like sulfur and ammonia

  24. Releasing Energy • Bacteria can release energy through cellular respiration (requires oxygen) or fermentation (does not require oxygen)

  25. Bacteria in Nature • Decomposers • Help recycle nutrients and sewage treatment • Nitrogen Fixers • Convert nitrogen gas to a useable form for plants

  26. Bacterial Toxins • Toxins- chemical compounds that are poisonous to eukaryotic cells • Can contaminate food • Food poisoning • Most can be killed by boiling water or various chemicals or using antibacterial produces • Sterilization- the process of destroying the bacteria on a nonliving surface by extreme heat or chemicals

  27. Biowarfare • Biowarfare is the deliberate exposure of people to biological toxins or pathogens such as bacteria or viruses

  28. Antibiotics • Antibiotics are used to block the growth and reproduction of bacteria • Many bacteria have become resistant to antibiotics

  29. Importance of Bacteria • Food processing • Pickles, cheese, vinegar, olives, sourdough bread • Digest oil spills • Synthesize drugs and chemicals

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