Bacteria & Viruses

1. Bacteria & Viruses Living or Non-living

2. Bacteria • Prokaryotes = unicellular organisms with no nucleus • General characteristics • Cell membrane surrounded by a thick, protective cell wall • Genetic material contained on a single strand of circular DNA – plasmid • Lack mitochondria, chloroplasts and other membrane bound structures

3. Two New Kingdoms • Archaebacteria or “ancient bacteria” • Live in extreme environments • Cell wall lacks peptidoglycan • Cell membrane contains lipids not found in any other organism • Many cannot survive in the presence of oxygen • Eubacteria or “true bacteria” • Thick, rigid cell walls of peptidoglycan • Cell wall surrounds a cell membrane • Diverse

4. Types of Bacteria • Round or spherical = coccus (cocci) • Rod shaped = bacillus (bacilli) • Spiral or corkscrew shaped = spirillum (spirilla) • Named for shape and arrangement of bacteria ex. Staphylococcus or Streptococcus

6. Reproduction in Bacteria • Binary fission – splits into two daughter cells • Conjugation – part of the genetic information from one cell is transferred to another through a bridge connecting both cells • Transformation – pick up bits and pieces of DNA from other bacteria allowing them to pick up new traits

7. Protective behavior • Bacteria can make endospores • Protective capsules • Allow bacteria to remain dormant until appropriate conditions exist • Can remain dormant for years

8. Harmful Bacteria • Infect other foods and cause illness • Infect other organisms • Pathogenic • Treated with antibiotics • Antibiotic resistance

9. Helpful Bacteria • Biotechnology • Insulin production • Gene splicing • Recombinant DNA • Useful in a variety of products • Certain cheeses • Yogurt – active cultures • Sauerkraut • Part of metabolism • Example: aids in digestion

10. Viruses • Tiny “particle” made of genetic material and protein that can invade and replicate within a living host. • General structure • Protein coat called a “capsid” • Protein coat “tricks” host cells into letting the virus in • Nucleic acid core

11. Viruses • Viruses are species specific • Types of Viruses – classified according to nucleic acid content • DNA viruses • RNA viruses • Retroviruses

12. Viruses • TMV – tobacco mosaic virus first discovered by Wendell Stanley. • Bacteriophage is a virus that infects bacteria.

13. Viral Reproduction • Can only reproduce when they invade or infect a host cell. • Lytic cycle • Injects its genetic material into a host • Immediately takes over the cells metabolic functions • Hosts DNA is used to make viral DNA & the host cell makes new viral genes and proteins until it bursts. • 5 Step Process

14. Viral Reproduction • Retroviruses • Contain RNA • Make DNA copies of their RNA genes and then insert them into the host cells chromosomes • Remain dormant, then become active • Direct production of new viruses and kills the host cell • Example: HIV which causes AIDS

16. Bacterial Disease in Humans • Pathogens = disease causing agents • Pasteur – “germ theory of disease” • Some bacteria damage cells and tissues by breaking them down to use for food • Mycobacterium tuberculosis • Some bacteria release toxins that interfere with the normal activities of the host. • Diptheria • Streptococcus bacterium • Scarlet fever

17. Preventing Bacterial Disease • Antibiotics • Block growth and reproduction of bacteria • Bacterial resistance to antibiotics • Vaccines – stimulate the body’s immune system • Weakened or killed strain of the disease • Stimulates the body to form antibodies

18. Bacterial Disease in Animals • Many bacteria can affect both animals and humans • Requires special precautions to protect livestock from infection • Example: Bacillus anthracis or “anthrax”

19. Diseases Caused by Bacteria • Lyme disease • Tetanus • Tuberculosis • Diptheria • Bacterial meningitis • Strep throat • Tooth decay

20. Controlling Bacteria • Sterilization by heat • Food storage and processing • Refrigeration slows down bacterial growth • Boiling, frying or steaming foods • Preserving foods • Disinfectants = chemical solutions that kill pathogenic bacteria • Concern with overuse - resistance

21. Viral Diseases in Humans and Animals • Viruses produce disease by disrupting the body’s normal equilibrium • Attack and destroy specific cells in the body. • Poliovirus – attacks the nervous system • Some viruses cause infected cells to change their patterns of growth and development. • Some cancers

22. Diseases Caused by Viruses • Common cold • Influenza • Small pox • Warts • AIDS • Chickenpox • Measles • Hepatitis A, B and C • West Nile Virus • Polio

23. Viroids and Prions – virus-like particles • Viroids – cause disease in plant • Single stranded RNA molecules with no surrounding capsid • Infect cells by making them synthesize new viroids • Disrupt plant metabolism and stunt plant growth

24. Viroids and Prions • Prions – cause disease in animals • First discovered in sheep but also found in other animals including humans • Cause disease by forming protein clumps which interfere with normal protein production • Particles contain no DNA or RNA, only proteins • Prions = “protein infectious particles”