Bacteria and Viruses

1. Bacteria and Viruses Chapter 19

2. Bacteria • All are PROKARYOTIC – • Meaning they are all unicellular (entire organism is only one cell), • and they have No Nucleus. • Range in size from 1 – 5 micrometers. • 2000 to 10,000 bacteria cells could fit on a penny!!!!

3. Classifying Prokaryotes • Until recently, all placed in Kingdom Monera. • Now divided into two Kingdoms: • Eubacteria – common bacteria • Archaebacteria – “ancient” bacteria

4. Archaebacteria • Look a lot like eubacteria under microscope. • Lack peptidoglycan and have different membrane lipids. • DNA sequence more like DNA sequence of Eukaryotes, than is eubacteria.

5. Live in extremely harsh environments – hot springs, volcanoes, deep sea vents, oxygen-free intestine of animals.

6. Eubacteria • Larger kingdom of prokaryotes • Live on land, fresh water, salt water, on plants, and in animals – including humans • Surrounded by cell wall that protects and determines organisms’s shape. • Cell wall made of peptidoglycan

7. Ribosome Cell wall Cell membrane Peptidoglycan Pili Flagellum DNA Bacteria Cell Bacteria have DNA. Since they are prokaryotes the DNA is not contained in a nucleus.

8. CHARACTERISTICS • Bacteria are prokaryotes • Have no membrane bound organelles and no nucleus • Bacteria live in a wide range of environments • STRUCTURE • Bacteria are unicellular (one-celled living organisms) • Bacteria contain a cell • wall

9. Some bacteria contain pili • extensions of the plasma membrane help bacteria stick to surfaces • Bacteria contain flagella • enable bacterial cells to move • Some bacteria contain capsules • prevent bacteria from being easily engulfed and digested.

10. Identify Prokaryotes • Prokaryotes are identified by characteristics such as: • shape, • cell walls, • the way they move, • the way they obtain energy.

11. Types of Bacteria

12. Cell Shape

13. Bacilli – rod shaped bacteria • Cocci – spherical shaped bacteria • Spirilla – spiral or cork-screw shaped bacteria • Staphylococusaureus – spherical bacteria that cause skin infections • Escherichia coli – found in our intestines, synthesize vitamin K • Leptospira sp. – a spiral shaped bacterium infects the liver or the brain. • Streptococcus bacteria – cause strep throat, are spherical, and form chains • Bacterial names refer sometimes to their morphology (form or structure): • the prefix Staphylo – refers to a group, therefore staphylococcus is a group of spherical bacteria.

17. Cell Walls • Prokaryotes can be classified on whether or not their cell walls contain peptidoglycan, • Can also be grouped by how much peptidoglycan is present in the cell walls. • Gram positive (stain purple) – have thick peptidoglycan in cell walls. • Gram negative (stain pink) – have thin layer of peptidoglycan in cell walls.

18. Movement • Can be categorized bases on how they move: • Propelled by tail-like flagella • Snake-like movement • Glide along slime secretion • No movement at all

19. How they Obtain Energy • Heterotroph – must take in organic molecules sustain life. • Chemoheterotrophs • Photoheterotrophs • Autotrophs – make all the organic molecules needed to sustain life • Photoautotrophs • Chemoautotrophs

20. Importance of Bacteria • Bacteria are vital to maintaining the living world: • Some are producers that capture energy by photosynthesis. • Others are decomposers – breaking down the nutrients in dead matter and the atmosphere. • Still other bacteria have human uses.

21. Bacteria are helpful and harmful LIVING organisms • Helpful: • Cheese and yogurt are produced as the results of metabolism by certain bacteria • Some bacteria produce antibiotics that are used to kill other bacteria • Play a role in human digestion and other life processes • Harmful: • Some bacteria cause disease (about ½ of all human diseases are caused by bacteria)

22. Diseases Caused by Bacteria • Dental Plaque (film destroys tooth enamel) • Strep Throat • Pneumonia • Diphtheria (causes a false membrane to form in the respiratory system which blocks air passages)

23. How to Treat Bacterial Infections • Antibiotics • Different types of bacteria require different antibiotics. To make sure that you get the right treatment, your doctor may take a sample (a swab from the throat or a urine sample) • Do not take antibiotics if you don’t have a bacterial infection. You are only making the bacteria smarter!

24. Viruses – “Poison” • Viruses are particles of nucleic acid, protein, and in some cases, lipids. • They can only reproduce by infecting living cells. • Viruses differ greatly in size and structure. • Main mechanism: they enter living cells and use the infected cells components to produce more viruses.

25. Characteristics of Viruses • Nonliving, but they do have nucleic acids and proteins. • Harmful: yes, they can make you sick • Genetic information: An inner core made up of nucleic acid (either DNA or RNA) • Does not require food • Does not grow or move

26. Virus Structure • Most viruses are so small they can only be viewed with an electron microscope. • A typical virus is composed of a core DNA or RNA surrounded by a protein coat. • A viruses protein coat is call a capsid.

27. Structure of Viruses • An inner core made up of nucleic acid • Either DNA or RNA • Contains the genetic material • Outer coat of protein • Capsid • The protein coat gives the virus its shape

28. RNA DNA Head RNA Capsid Capsid proteins Tail sheath Tail fiber Surface proteins Membrane envelope Tobacco Mosaic Virus T4 Bacteriophage Influenza Virus

29. How Viruses Work • The capsid includes proteins that enable the virus to enter a host cell. • The capsid proteins bind to receptors on the surface of a cell and “trick” the cell into allowing the virus inside. • Once the virus is in the host cell, the virus’s DNA or RNA codes for the host cell to replicate the viruses genetic information.

30. Often times, the host cell is destroyed in the process of viral replication. • Because viruses must bind precisely to its host cell to be able to “trick” the cell, viruses are very specific to the type of host cell they can invade.

31. Types of viruses • Plant viruses must invade plant cells to replicate. • Animal viruses must invade animal cells to replicate. • Viruses that infect bacteria cells are called bacteriophages.

32. Viral Infections • In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst. • In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell’s DNA.

34. Reproduction of Viruses • Cannot reproduce alone • Can reproduce ONLY inside a living host cell

35. Diseases Caused by Viruses • Common cold • Influenza (Flu) • Smallpox • Warts • AIDs • Caused by the Human Immuno-deficiency Virus (HIV) • Attacks the immune system (Helper T Cells)

36. Treatment of Viruses • Treatment of viral infections is usually left up to the patient's own immune system. There is no cure for viruses! • Vaccines introduce dead or weakened viruses into your body so your cells will produce antibodies to protect from future viral infection.

37. Why isn’t there a cure for viruses? • Viruses replicate in the body’s cells. • If you destroy the virus, you are destroying your own body cells.

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