Ch 19- Bacteria and Viruses

1. Ch 19- Bacteria and Viruses • http://player.discoveryeducation.com/index.cfm?guidAssetId=9A7AFEE4-3E11-4820-8597-5403F1802ADA&blnFromSearch=1&productcode=US • Prokaryote- unicellular organisms that lacks a nucleus • How do the two groups of prokayotes differ? • Make up of cell walls • Archaebacteria lack peptidoglycan, have different membrane lipids • DNA sequence is more like eukaryotes than eubacteria • Thought to be ancestors of eukaryotes • Eubacteria live almost everywhere and archaebacteria live in extremely harsh environments • What factors are used to identify prokaryotes? • Shape • Chemical nature of their cell walls • Movement • How they obtain energy

2. Identifying Prokaryotes • Shapes • Bacilli are rod shaped • Cocci are spherical shaped • Spirilla are spiral and corkscrew shaped • Cell walls- gram staining to tell apart • Gram positive- thick peptidoglycan walls, appear violet • Gram negative- thinner walls, appear pink or light red • Movement- some move and some don’t • Flagella- whiplike structures used for movement

3. Metabolic Diversity • Heterotrophs- consume organic molecules made by other organisms • Chemoheterotrophs- take in organic molecules • Photoheterotrophs- photosynthetic and take in organic compounds for carbon source • Autotrophs- produce own food • Photoautotrophs • Chemoautotrophs- do not require light, use energy from chemical reactions

4. Growth and Reproduction • Binary fission- form of asexual reproduction where cell doubles in size, replicates DNA and divides in half, produces two identical daughter cells • Conjugation- the exchanging of genetic information between bacteria • Endospore- forms when growth conditions become unfavorable • Bacterium produces thick internal wall, encloses DNA, remains dormant for months or years

5. Importance of Bacteria • What is the importance of bacteria? • Vital to maintaining living world • Producers and decomposers • Decomposers recycle nutrients • Nitrogen fixation- converting nitrogen gas into form plants can use • Used in foods and beverages • E. coli break down food in intestines • Bacteria in extreme environments- rich source of heat stable enzymes • Medicine, food production, industrial chemistry

6. Sec 2- Viruses • What is a virus? • Composed of core of DNA or RNA surrounded by protein coat • Reproduce only by infecting living cells • Enter living cells, use infected cell to produce more viruses • Vary greatly in size and structure • Welcome to Discovery Education Player • Capsid- virus’s protein coat • Most are highly specific to cells they infect • Bacteriophages- viruses that infect bacteria

7. Viral Infection • Lytic infection- virus enters a cell, makes copies of itself, and causes the cell to burst • Injects host cell with viral DNA, mRNA is made by the host cell from viral DNA into viral particles • Lysogenic infection- virus integrates its DNA into the DNA of the host cell • Viral genetic information replicates along with host cell’s DNA • Does not lyse the host cell right away • Prophage- viral DNA that is embedded in the host’s DNA • May stay for many generations

8. Retroviruses • Viruses that contain RNA as their genetic information • Produce a DNA copy of their RNA, inserted into DNA of host cell • May remain dormant for lengths of time, directing production of new viruses-cause death of new cell • Responsible for some types of cancer • Acquired immune deficiency syndrome (AIDS)

9. Are viruses alive? • Reproduction • Only within host cell • Regulate gene expression • Genetic code • DNA or RNA • Evolve • Do not……… • Grow or develop • Obtain and use energy • Respond to environment • Viruses are completely dependent upon living things

10. Sec 3- Diseases Caused by Bacteria and Viruses • Pathogens- disease-causing agents • How do bacteria cause disease? • Damage the cells and tissues of infected organism directly by breaking down the cells for food • Release toxins or poisons that travel throughout the body interfering with the normal activity of the host • Mycobacterium tuberculosis- causes tuberculosis, destroys lung tissue • Streptococcus- causes strep throat, releases toxins in bloodstream and can cause scarlet fever • Corynebacteriumdiphtheriae- causes diphtheria, releases toxins into bloodstream that destroy tissue, can lead to trouble breathing, heart failure

11. How to prevent disease? • Vaccine- preparation of weakened or killed pathogens • Prompts body to produce immunity to disease • Immunity- body’s ability to destroy new pathogens • Antibiotics- compounds that block the growth and reproduction of bacteria • Penicillin

12. How can bacterial growth be controlled? • Sterilization, disinfectants, and food processing • How do viruses cause disease? • Produce disease by disrupting the body’s normal equilibrium • Many attack and destroy certain cells in body • Cause symptoms of disease • Poliovirus • Other cause cells to change patterns of growth and development • Cannot be treated with antibiotics

13. Viruses in animals • Foot-and-mouth disease infected cattle, sheep, and pigs in Europe in late 90’s • Viruses in plants • Tobacco mosaic virus • Difficult with cell walls • Viroids- single stranded RNA molecules that have no surrounding capsids • Prions- protein infectious particles, contain no DNA or RNA • May be cause of mad cow disease