1. Bacteria and Viruses
Chapter 20

2. Bacteria
Prokaryotes – single-celled organisms that do not have membrane bound organelles
Has three shapes:
Bacillus – rod-shaped
Coccus – sphere-shaped
Spirillum – spiral-shaped

3. Bacterial Structures Plasmid – a circular DNA molecule in bacteria
Ribosome – site of protein synthesis
Cell wall
Cell membrane

4. Bacterial Structures
Flagella – long whiplike projection that moves side to side
Cytoplasm – gel-like substance found inside the cell
Ring of DNA

5. Obtaining Energy and Nutrients
Photoautotrophs – organisms that get their energy from sunlight through photosynthesis
Ex. – cyanobacteria
Chemoautothrophs – the only organisms that can get their energy from inorganic sources
Inorganic – does not contain carbon atoms
Heterotrophs

6. Reproduction Binary fission – reproduce by asexual reproduction
A single cell divides into two identical cells
Conjugation – occurs when two bacteria exchange genetic material

8. Viruses
Viruses are not considered living because they can’t reproduce on their own, and they can’t grow

9. Viral Structures
Nucleic acid – The genetic material of a virus can be either DNA or RNA
Capsid – the protein coat
Envelope – a membrane surrounding the capsid
Envelope

10. Viral Structures
Tail fibers – function like a tiny syringe which injects the viral DNA into its bacterial host
Bacteriophage – viruses that infect bacteria
Bacteriophage

11. Reproduction
Lytic cycle – viral replication that results in the destruction of a host cell and the release of many new virus particles

13. Reproduction
Lysogenic cycle – viral replication in which viral genetic information is made without immediately destroying the host cell
Viruses undergo lysogentic cycles can remain dormant

15. Viroids and Prions Viroid – a single strand of RNA that has no capsid
Viroids cause abnormal development and stunted growth in plants

16. Viroids and Prions
Prions – misshapen versions of proteins that are found in the brain
They attach to normal proteins and cause them to take on the shape of the prion

17. 20.3 – Bacteria, Viruses, and Humans

18. Bacteria and the Environment
Bacteria produce oxygen, make nitrogen available to other organisms, and help decompose dead organisms.

19. Bacteria and Industry
Foods, such as pickles, soy sauce, and sourdough bread, are made by using bacteria
Bacteria is used in cleaning up oil spills and in sewage treatment plants

20. Koch’s Postulates
Robert Koch, a German physician, developed a technique for diagnosing a pathogen
Pathogen – an organism or virus that causes disease

22. Bacterial Diseases
Bacteria can cause disease by producing toxins and by destroying body tissues
Toxins – poisonous chemicals
Ex. of toxins – Foods contaminated with bacteria can cause food poisoning.
Ex. of destroying body tissues – necrotizing fasciitis

23. Antibiotic Resistance
Antibiotics – chemicals that inhibit the growth of or kill bacteria
Antibiotic resistance – the ability of bacteria to tolerate antibiotics

25. Antibiotic Resistance
Penicillin was used for most bacterial infections
Do not overuse antibiotics
Ex. of resistance – hand sanitizer

26. Viral Diseases
Because viruses enter the host cells to reproduce, it’s difficult to develop a drug that kills the virus without harming the living cell.
Antibiotics are not designed to kill viruses
Vaccine – a weakened form of a pathogen that prepares the immune system to recognize and destroy the pathogen
Ex. – flu shot