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Chapter 19 Bacteria and Viruses 19-1: Bacteria. Recently prokaryotes were split into two different groups; eubacteria and archaebacteria Bacteria are.

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Presentation on theme: "Chapter 19 Bacteria and Viruses 19-1: Bacteria. Recently prokaryotes were split into two different groups; eubacteria and archaebacteria Bacteria are."— Presentation transcript:

1 Chapter 19 Bacteria and Viruses 19-1: Bacteria

2 Recently prokaryotes were split into two different groups; eubacteria and archaebacteria Bacteria are prokaryotes

3 They have a cell wall for protection – the wall contains a carbohydrate for extra support Some even have another membrane that sits outside the cell membrane Eubacteria: a very wide range of prokaryotes that can live almost anywhere

4 They lack the carb in their cell wall that eubacteria have Archaebacteria: many live in very harsh environments Their DNA is also more like eukaryotes than the DNA of eubacteria

5 There are 3 main bacteria shapes; bacilli (rod-shaped), cocci (spherical), and spirilla (corkscrew-shaped) Prokaryotes are identified by things like shape, their cell wall, movement, and they way they get energy

6 Gram positive appears purple and means the cell wall has the carb Gram negative appears pink and means the cell wall doesn’t have the carb There are 2 different types of cell walls; a Gram stain can be used to tell them apart A Gram stain test uses 2 different dyes to tell if the cell wall contains a specific carbohydrate

7 Photoautotrophs use light energy to make they energy the need (almost like plants) Chemoautotrophs use carbon molecules from carbon dioxide to make the energy they need Most prokaryotes are heterotrophs, but some are autotrophs Some prokaryotes do not move, some are propelled by flagella, some spiral forward, some slide along in slime they secrete

8 Obligate aerobes must have oxygen Obligate anaerobes cannot live with oxygen Some bacteria need oxygen, while others are killed by it Facultative anaerobes can live with or without oxygen

9 Conjugation = when a hollow bridge forms between 2 bacteria so they can exchange genetic info Bacteria can grow and reproduce in different ways Binary fission = when a bacterium has grown large enough that it can replicate its DNA and split in two

10 Bacteria can form spores  bacteria DNA gets surrounded by a thick cell wall Spores can lay dormant until conditions are favorable for more growth – this lets bacteria survive harsh conditions Anthrax

11 While we tend to think of bacteria as a bad thing, many bacteria are very useful Uses include decomposition, nitrogen fixation, food production, helping humans produce vitamins, digestion of oil and poison, etc…

12 19-2: Viruses

13 They vary in terms of shape and size Viruses are particles of nucleic acid, protein, and sometimes lipids Viruses can reproduce only by infecting living cells

14 Capsid = the protein coat The proteins bind to the host cell and trick the cell into letting it in A typical virus is composed of a core of DNA and RNA surrounded by a protein coat Once the viral DNA is inside the cell it uses transcription and translation to create more proteins

15 Most viruses are very specific to the type of cell they will infect Bacteriophages only infect bacteria

16 In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, and the viral genetic info replicates along with the host cell DNA Once a virus is inside a cell, two things can happen In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst

17 Once a retrovirus enters a cell, it makes a DNA copy of its RNA The new DNA gets inserted into the DNA of the host cell and can stay dormant for some time A retrovirus contains RNA as its genetic code

18 Retroviruses can cause some types of cancer in animals The virus that causes AIDS is a retrovirus

19 CharacteristicVirusCells (bacteria and others) StructureDNA or RNA core, capsid Cell membrane, cytoplasm ReproductionOnly within a host cell Independent cell division Genetic CodeDNA or RNADNA Growth and development NoYes Obtain and use energy NoYes Response to environment NoYes Change over timeYes Comparison of viruses and bacteria

20 Viruses are not considered living even though they have many characteristics of living things Viruses are considered parasites since they must infect a living cell to grow and reproduce

21 19-3: Diseases caused by Bacteria and Viruses

22 Some bacteria damage cells and the tissues of the infected organism directly by breaking down the cells for food Ex. The bacterium that causes tuberculosis is inhaled into the lungs and destroys lung tissue Bacteria produce disease in one of two general ways Some bacteria damage cells and the tissues of the infected organism directly by breaking down the cells for food Ex. The bacterium that causes tuberculosis is inhaled into the lungs and destroys lung tissue

23 Other bacteria release toxins that travel throughout the body interfering with the normal activity of the host Ex. The bacterium that causes strep throat releases toxins in the bloodstream  these can even cause scarlet fever.

24 Many bacterial diseases can be prevented with vaccines Antibiotics can be used to treat bacterial infections that have already occurred Other examples of bacterial infections are lyme disease, tetanus, bacterial meningitus, and tooth decay

25 There are various methods used to control bacterial growth, including sterilization, disinfectants, and food processing Bacterial diseases can be seen in animals – many bacteria can affect both humans and animals Ex. Anthrax

26 In many viral infections, viruses attack and destroy certain cells in the body Examples include the common cold, influenza, smallpox, AIDS, chickenpox, measles, and west nile Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium

27 Viral diseases CANNOT be treated with antibiotics The best way to protect against viral infections is with vaccines Viruses can produce serious animal diseases also

28 Many viruses infect plants and cause serious threats to agricultural crops - ex. Tobacco mosaic virus and potato yellow dwarf virus


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