Bacteria and Viruses

1. Bacteria and Viruses Chapter 19

2. anthrax Strep throat

3. 19-1 BACTERIA • BACTERIA ARE CLASSIFIED AS PROKARYOTES – UNICELLULAR ORGANISMS THAT LACK A NUCLEUS • CLASSIFYING PROKARYOTES • EUBACTERIA – LARGER OF THE TWO KINGDOMS • LIVE IN FRESH WATER, SALT WATER, LAND, AND ON AND IN HUMAN BODY.

4. Prokaryotes • Traditionally all prokaryotes were classified as Monerans • Also known as bacteria (p.) or bacterium (s.) • Presently, prokaryotes are divided into two kingdoms Archaebacteria & Eubacteria

5. 1. K. Eubacteria • Larger of the two kingdoms • Live almost everywhere • Vital for life functions and industry • Both helpful and harmful (E. coli!)

6. 2. K. Archaebacteria • Believed to be earliest organisms to inhabit the Earth • All live in harsh environments • DIFFER FROM EUBACTERIA BY: • NO PEPTIDOGLYCAN • DIFFERENT MEMBRANE LIPIDS • DNA more like eukaryotes’ DNA • 3 separate phyla…

7. 1. Methane-producing bacteria (methanogens) • Intestinal tracts of animals • Bottoms of swamps • Used for sewage treatment

8. 2. Salt-loving bacteria (Halophiles) • Thrive in high salinity waters where no other life can exist. • Great Salt Lake • Dead Sea

9. 3. Hot-acidic loving (thermoacidophiles) • Thrive at temperatures as great as 180ºF and pHs as low as 2. • Natural springs. • Yellowstone National Park

10. Facts about bacteria: • Found everywhere • Very small. Much smaller than any cell in our body. • No membrane-bound structures or nucleus. (prokaryotes) • Usually surrounded by a cell wall and a capsule for additional protection.

11. General structure:

12. IDENTIFYING PROKARYOTES • IDENTIFIED BY SHAPE, CELL WALLS, MOVEMENT - FLAGELLA, WAY THEY GET ENERGY • SHAPES: • BACILLI (RODS), COCCI (SPHERES), SPIRILLA (SPIRAL)

13. Classification according to shape. • Coccus (spherical) • Can be single cells, pairs, or chains • Example: Strep throat

14. 2. Bacillus (rod) • Single cells • Pairs • Chains • Example: anthrax

15. 3. Spirillum(spiral) • Only exist as single cells Example: cholera, syphilis

16. Shapes:

17. 4 Ways to Classify Bacteria 1. shape 2. Chemical nature of cell walls (Gram + or gram -) 3. How they move 4. How they obtain energy

18. Gram-positive bacteria • Two kinds of cell walls in Eubactiera • Gram-positive bacteria have cell walls that are dyed a violet stain. • Can be harmed by antibiotics like penicillin • example: streptococcus

19. Gram-negative bacteria • More difficult to penetrate cell wall. • Appear pink/red in Gram stain • Usually more difficult to treat with antibiotics • Example: E-coli

20. Movement • Usually move through flagella or gliding along a surface.

21. Aerobic The most common type Cannot live without oxygen Anaerobic Cannot live in the presence of oxygen Gets energy through fermentation (CO2) Metabolic Needs

22. Saprobes Feed off the remains of dead plants and animals. Seldom cause disease Parasites Live on or in other living organisms. Often cause disease Heterotrophic bacteria

23. 2 types of heterotrophic bacteria • Chemoheterotrophs – take in organic molecules for energy and carbon (like humans!) • Largest group of bacteria! • Photoheterotrophs – use sunlight for energy, but also need to take in organic compounds

24. Photoautotroph Use sunlight to convert carbon dioxide into energy In lakes/streams/ oceans Ex. cyanobacteria Chemoautotroph Use inorganic chemical compounds to convert carbon dioxide into energy. Autotrophic bacteria

25. Releasing Energy 1. Obligate aerobes: require oxygen 2. Obligate anaerobes: cannot live in presence of oxygen 3. Facultative anaerobes: do not need oxygen, but can live in the presence of it (E. coli)

26. Growth and Reproduction 1. Binary fission: cell divides, asexual 2. Conjugation: transfer of genetic information from one cell to another, sexual 3. In unfavorable conditions, many bacteria can form endospores – can remain dormant for months or years (such as anthrax)

27. Genetic material • Nucleoid= a single circular chromosome containing the DNA and RNA. • Endospore = tough protective coat that covers and protects the nuclear material.

28. Reproduction • All reproduce asexually • Usually through binary fission • Under certain conditions, bacteria can reproduce very quickly • A small colony can double in 20 minutes. • animation

29. Binary fission • The most common type of asexual reproduction. • A single cell splits to form two daughter cells

30. Exchange of DNA Conjugation = genes move from one cell to another

31. Endospores • A thick covering around the DNA that allows the bacterium to remain dormant for long periods of time. If necessary, many years.

32. Importance of Bacteria • Without bacteria, we would die! • Bacteria produce energy, decompose dead matter into nutrients, convert nitrogen for plants, and produce vitamins in our intestines

33. Helpful bacteria • Decompose food wastes • Produce antibodies • Genetic engineering – bacteria can produce heat-stable enzymes for medicines • Decomposition of dead plants and animals • Industry & agriculture – cleaning oil spills • Break down sewage into water, carbon dioxide, nitrogen

34. Bacteria on Plant roots • Can be helpful in ‘fixing’ nitrogen for plant use. • Rhizobium nodules on roots of soybeans convert nitrogen into ammonia

35. Controlling Bacteria 1. Sterilization: destroy bacteria by subjecting them to great heat or chemicals a. Boiling, frying, steaming can all kill bacteria b. Disinfectant chemical solutions can be used in homes and hospitals 2. Refrigeration – bacteria grow slowly at low temperatures

36. VIRUSES • Are they living or non-living? • Contain genetic material • Lack organelles • Cannot reproduce unless inside a host cell. • The word virus comes from the Greek word for POISON • Cause many diseases.

37. Section 19.2 Viruses • Viruses: particles of nucleic acid and protein 1. Nucleic acid = DNA or RNA that contains instructions for making new copies of the virus 2. Capsid: outer protein coat

38. How big is a virus? • Much smaller than bacterial cells. • Scientists have only recently, last 60 years, learned anything about viruses • Classified according to the types of cells they attack.

39. Virus structure: • A center core of DNA or RNA surrounded by a protein coat called a capsid.

40. Viral Body Plans • Genetic material is DNA or RNA • Coat is protein Complex virus (bacteriophage) Helical virus Polyhedral virus

41. DNA and RNA Review DNA – deoxyribonucleic acid chemical compound (containing hydrogen, oxygen, nitrogen, carbon, and phosphorus) with instructions for coding proteins that determines your genetic makeup RNA – ribonucleic acid - nucleic acid that contains the sugar ribose

42. Viral Infections A virus binds to proteins on a cell and enters the cell • 1. Infect cells and replicate inside host cell • 2. Bacteriophage: viruses that infect bacteria

43. 2 types of viral infections a. Lytic infection: virus enters cell, makes copies of itself and causes the cell to burst b. Lysogenic infection: virus embeds its DNA into DNA of host and is replicated with host cell’s DNA

44. LYTIC CYCLE Injects its nucleic acid (DNA or RNA) into the cell to take over cellular activities. LYSOGENIC CYCLE Coexists with the cell without destroying the host cell 2 main types of viral reproduction:

45. Lytic cycle

46. Lysogenic cycle

47. The Prophage • Prophage = viral DNA that is inserted into a cell • The prophage can have the cell make copies of the virus right away or may wait several generations (a latent infection) and then begins making copies at a later time

48. Viruses and Disease 1. Many viruses can be prevented through the use of vaccines (polio, measles, influenza) 2. Oncogenic viruses cause cancer 3. Retroviruses contain RNA 4. Prions contain no DNA or RNA, only protein

49. RNA VIRUS • Direct the production of proteins by the host cell. • RETROVIRUS = A special type of virus that can make DNA which will produce new RNA, which, in turn, makes proteins that produce new viruses. • Ex. AIDS virus ( HIV )

50. Bacteria and Disease 1. Pathogen: disease-causing agents 2. 2 ways bacteria cause disease a. Break down tissues for food b. Release toxins to interfere with normal cellular activity 3. Many can be prevented with vaccines, can be treated with antibiotics