1. Unit 6 Microorganisms & Fungi Ch. 19 Bacteria & Viruses

2. Bacteria Prokaryotes - unicellular organisms that lack a nucleus The smallest & most common microorganism

3. Classifying Prokaryotes Prokaryotes are divided into 2 separate kingdoms: eubacteria & archaebacteria

4. Classifying Prokaryotes Eubacteria are surrounded by a cell wall that protects the cell from injury & determines its shape

5. Classifying Prokaryotes Archaebactertia live in extremely harsh envrionments May be found in oxygen-free envrion. like thick mud & the digestive tracts of animals Some live in salty environ. like Utah’s Great Salt Lake Others are found in hot springs where temps. approach the boiling point of water

6. Identifying Prokaryotes Prokaryotes are identified by characteristics such as shape, the chemical nature of their cell walls, the way they move, & the way they obtain energy

7. Identifying Prokaryotes Bacilli - rod-shaped bacteria Cocci - round bacteris Spirilla - spiral-shaped bacteria

8. Identifying Prokaryotes 2 different types of cell walls are found in eubacteria Gram staining is a method used to tell them apart Gram-positive bacteria have a peptidoglycan wall Gram-negative bacteria have a lipid layer

9. Metabolic Diversity Chemoheterotrophs - most heterotrophic prokaryotes take in organic molecules for both energy & a supply of carbon Includes most animals, even humans

10. Metabolic Diversity Photoheterotrophs - heterotrophic prokaryotes that are photosynthetic, using sunlight for energy, but also need to take in organic compounds as a carbon source

11. Metabolic Diversity Photoautotrophs - autotrophs that use light energy to convert carbon dioxide & water to carbon compounds & oxygen Found where light is plentiful

12. Metabolic Diversity Chemoautotrophs - prokaryotes that can perform chemosynthesis Like photoautotrophs, they make organic carbon molecules from carbon dioxide However, they do not require light as a energy source They use energy directly from chemical reactions involving ammonia, hydrogen sulfide, nitrites, sulfur, or iron

13. Metabolic Diversity Obligate aerobes - organisms that require a constant supply of oxygen in order to live Obligate anaerobes - bacteria that must live in the absence of oxygen Facultative anaerobes - bacteria that can survive with or without oxygen

14. Growth & Reproduction Binary fission - when a bacterium has grown so that it has nearly doubled in size, it replicates (copies) its DNA & divides in half, producing 2 identical “daughter” cells

15. Growth & Reproduction Conjugation - when a hollow bridge forms between 2 bacterial cells, & genes move from 1 cell to another

16. Growth & Reproduction Endospore - a type of spore that is formed when a bacterium produces a thick internal wall that encloses its DNA & a portion of its cytoplasm Allows some bacteria to survive harsh conditions like extreme heat, dryness, or lack of nutrients

17. Importance of Bacteria Bacteria are vital to maintaining the living world Some are producers that capture energy by photosynthesis Others are decomposers that break down the nutrients in dead matter & the atmosphere Still other bacteria have human uses

18. Importance of Bacteria Nitrogen fixation - the process of converting nitrogen gas into a form that plants can use Allows nitrogen atoms to continually cycle through the biosphere Certain bacteria produce nitrogen compounds, naturally

19. Importance of Bacteria Human uses: Used to clean up oil spills because they digest petroleum Some remove waste products & poisons from water Some synthesize drugs & chemicals in genetic engineering Some live in the human intestine, & make vitamins that the body cannot produce by itself

20. What is a Virus? Virus - particles of nucleic acid, protein, & sometimes, lipids They can reproduce only by infecting living cells Viruses enter living cells & use the machinery of the infected cell to produce more viruses

21. What is a Virus? A typical virus is composed of a core of DNA or RNA surrounded by a protein coat Capsid - a virus’s protein coat, it includes proteins that enable a virus to enter a host cell Bacteriophages - viruses that infect bacteria

23. Viral Infection In a lytic infection, a virus enters a cell, makes copies of itself, & causes the cell to burst Lytic infection - when the host cell is lysed, or burst open, & destroyed

24. Viral Infection In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, & the viral genetic information replicates (copies) along with the host cell’s DNA Lysogenic infections - when a host cell makes copies of the virus, indefinitely Prophage - the viral DNA embedded in the host’s DNA

26. Retroviruses Retroviruses - viruses that contain RNA as their genetic information After infecting a cell, they produce a DNA copy of their RNA (working backwards) Ex.) AIDS

28. Diseases Caused by Bacteria & Viruses Pathogens - disease-causing agents Disease can be considered a conflict between the pathogen & the host

29. Bacterial Disease in Humans Bacteria live on & in our bodies, some help us perform essential functions However, the growth of pathogenic bacteria disrupts the body’s equilibrium by interfering with its normal activities & producing disease

30. Bacterial Disease in Humans Bacteria produce disease in 1 of 2 general ways: They damage the cells & tissues of the infected organism by breaking down the cells for food They release toxins (poisons) that travel throughout the body interfering with the normal activity of the host

31. Preventing Bacterial Disease Vaccine - a preparation of weakened or killed pathogens When injected in the body, sometimes prompts the body to produce immunity to the disease Antibiotics - compounds that block the growth & reproduction of bacteria Only effective against BACTERIAL infections

32. Bacterial Diseases in Animals

33. Controlling Bacteria There are various methods used to control bacterial growth, including sterilization, disinfectants, & food processing

34. Viral Diseases in Humans Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium In many viral infections, viruses attack & destroy certain cells in the body, causing the symptoms of disease

35. Diseases Caused by Viruses