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Ch 19- Bacteria and Viruses

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1 Ch 19- Bacteria and Viruses
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? Welcome to Discovery Education Player
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 Regulate gene expression Genetic code
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 Corynebacterium diphtheriae- 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? How do viruses cause disease?
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 Prions- protein infectious particles, contain no DNA or RNA
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

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