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Acellular Microbes

Acellular Microbes. Infectious Agents. Viruses. Range from 10-300 nm. academic.pgcc.edu/.../Chapter%2013/size.html. All Organisms Have the Potential to be Infected by Some Type of Virus. Tobacco Mosaic Virus . www.ncbi.nlm.nih.gov/.../Milne /tobamo1.htm. Small pox virus.

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Acellular Microbes

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  1. Acellular Microbes

  2. Infectious Agents

  3. Viruses • Range from 10-300 nm. academic.pgcc.edu/.../Chapter%2013/size.html

  4. All Organisms Have the Potential to be Infected by Some Type of Virus. Tobacco Mosaic Virus. www.ncbi.nlm.nih.gov/.../Milne/tobamo1.htm Small pox virus. www.ncbi.nlm.nih.gov/ICTVdb/Images/Murphy/Dow.. E. Coli being attacked by lambda bacteriophage. www.asm.org/division/m/foto/LamAttack.html Leaf left = uninfected tobacco leaf. Right leaf = infected leaf. www.nature.com/.../v411/n6839/full/411848a0.html Man infected with small pox. www.idph.state.il.us/Bioterrorism/spoxphoto1.htm

  5. Sooooo……….what is a virus?

  6. Virus Characteristics • 1. Have genetic material, either DNA or RNA. • 2. Can’t replicate without a host cell. • 3. Can’t divide by binary fission, mitosis, or meiosis. • 4. Can’t make their own energy (steal it from host cell). • 5. Can’t make their own protein or genetic material (steal from host cell).

  7. Characteristics of a Typical Virus • 1. Consists of a genome of either RNA or DNA. • 2. Genetic material surrounded by a capsid or protein coat. • Composed of small protein units called capsomeres. • 3. Some viruses have an outer envelope. • 4. May also have a tail, sheath, and tail fibers.

  8. A Typical Virus

  9. Virus Classification • 1. Type of genetic material. • 2. Shape of the capsid. • 3. Number of capsomeres. • 4. Size of the capsid. • 5. Presence or absence of an envelope. • 6. Type of host it infects. • 7. Type of disease it produces. • 8. Target cell. • 9. Immunologic or antigenic properties.

  10. Viral Classification www.biotech100.com www.antibac2k.com

  11. Where did viruses come from?

  12. Virus Origin • 3 Major Theories • 1. Viruses are remnants of past infections (e.g. mitochondrion/chloroplasts). • 2. Cells came before viruses. • Viruses are degenerate cells or cell fragments. • 3. Viruses represent a separate evolutionary branch

  13. What if. . . . • Scientists found a cell that was as large or larger than some bacteria and that cell had the capabilities to produce almost everything it needed to “live.” • It required a host cell only to make some ribosomes. • Is it a virus or a living cell?

  14. Meet Mimi! http://www.microbiologybytes.com/virology/Mimivirus.html

  15. Retrovirus • Genetic information is single-stranded RNA. • Have a special enzyme called reverse transcriptase. • This enzyme makes DNA from RNA. • Integrate their newly formed double-stranded DNA into the host cell. • Example = HIV Human Immunodeficiency Virus (www.msu.edu)

  16. “Junk DNA” • Many retroviruses are responsible for “junk DNA” in our genome. Illustration by James Collins (www.rps.psu.edu )

  17. Sheep, Viruses, and Dr. Spencer

  18. Bacteriophage • A virus that infects bacteria. • 2 types • 1. Virulent Bacteriophage • 2. Temperate Bacteriophage

  19. Virulent Bacteriophage • Causes Lytic Cycle (5 steps) • 1. Attachment • 2. Penetration • 3. Biosynthesis • 4. Assembly • 5. Release textbookofbacteriology.net oceanworld.tamu.edu

  20. Temperate Bacteriophage • Do not immediately begin lytic cycle. • Their DNA remains embedded in bacterial cell chromosome.

  21. Animal Viruses www.heritageparkzoo.org • Species specific. • Attach to specific binding sites on cells. • This affects what species and which cell type is infected. • Multiplication of Animal Viruses (6 steps) • 1. Attachment • 2. Penetration • 3. Uncoating • 4. Biosynthesis • 5. Assembly • 6. Release

  22. Budding A transmission electron microscopy (TEM) image of influenza viruses budding from the surface of an infected cell. (CNRI/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc.)

  23. Antiviral Agents • Interfere with the phases of viral multiplication. • May disrupt a binding site. • May disrupt an enzyme or protein. • May interfere with the synthesis of viral parts like DNA, RNA, or protein synthesis.

  24. Oncogenic Viruses • Viruses that cause cancer. • Ex. Human papillomaviruses (HPV – wart viruses) cause different types of cancers. • i.e. cervical cancer and other types of cancers of the genital tract. Kaposi Sarcoma – caused by human herpesvirus 8. www.hyle.org

  25. Plant Viruses Maize chlorotic mottle virus (MCMV) nu-distance.unl.edu

  26. Viroids and Prions

  27. Viroids • Consist of short, fragments of single-stranded RNA. • Only found in plants (so far). • Can interfere with plant’s metabolism, resulting in the plant being stunted or killed. • Ex. Potato spindle tuber Left: normal potatoes; Right – infected potatoes www.unece.org

  28. Proteins Left = unfolded protein; Right = folded protein

  29. Prions Left = correct protein folding; Right = wrong protein folding www.cogs.susx.ac.uk

  30. Prions • Small infectious proteins. • Cause fatal neurologic diseases in animals. • Cause fatal spongiform encephalopathies. • Brain becomes riddled with holes. Brain with spongiform encephalopathy webs.wichita.edu

  31. Prion Animal Infections Deer infected with “chronic wasting disease.” (http://www.fw.delaware.gov) Sheep infected with scrapie. (www.gov.mb.ca) Bovine spongiform encephalopathy, “mad cow disease.”

  32. Prion Human Infections Kuru infected boy. Papua, New Guinea. pathology.mc.duke.edu Creutzfeldt-Jakob disease. www.nlm.nih.gov Fatal familial insomnia

  33. The End

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