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Viruses and Prokaryotes Chapter 18. Studying Viruses and Prokaryotes Virus – an infectious agent made up of a core of nucleic acid and a protein coat.

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Presentation on theme: "Viruses and Prokaryotes Chapter 18. Studying Viruses and Prokaryotes Virus – an infectious agent made up of a core of nucleic acid and a protein coat."— Presentation transcript:

1 Viruses and Prokaryotes Chapter 18

2 Studying Viruses and Prokaryotes Virus – an infectious agent made up of a core of nucleic acid and a protein coat. Virus – an infectious agent made up of a core of nucleic acid and a protein coat. Pathogen – any living infectious disease causing agent Pathogen – any living infectious disease causing agent

3 Studying Viruses and Prokaryotes Virus Virus Only reproduce in host Only reproduce in host DNA/RNA DNA/RNA Cannot Grow Cannot Grow Cannot use energy Cannot use energy Cannot respond to stimuli Cannot respond to stimuli CAN change over time CAN change over time Bacteria Bacteria Independent reproduction (sexual/asexual) DNA Grows and develops Uses energy for processes Responds to the environment Changes over time

4 Studying Viruses and Prokaryotes Viroids Viroids Infectious particles that cause disease in plants Single stranded RNA without protein coat Passed through seeds or pollen Major agricultural impact Prions Prions Infectious particle made only of proteins Causes proteins not to fold properly Play a role in some diseases of the brain Ex. Mad Cow Disease

5 Viral Structure and Reproduction Discovery Discovery Dmitri Ivanovsky - small bacteria or poisons – virus Tobacco mosaic disease Martinus Beijerinck – later suggested the cause of the disease was from particles in the juice Showed the disease agent passed through gel Tiny particles in the substance caused the disease Virus – Latin for poison

6 Viral Structure and Reproduction Simple structure Simple structure Virion – single virus particle Shape determines infection Capsid – viruses protein coat Contains either DNA or RNA In some viruses, protein coat surrounded by lipids Can form spikes used for attachment Used for identification- Enveloped, Helical, Polyhedral

7 Viral Structure and Reproduction Viruses can infect bacteria Viruses can infect bacteria Bacteriophage Bacteriophage Release enzymes that break down the bacterial cell wall Release enzymes that break down the bacterial cell wall Injects its DNA into the bacteria Injects its DNA into the bacteria Viruses infecting eukaryotes Viruses infecting eukaryotes My enter by endocytosis My enter by endocytosis Also can enter if in envelope Also can enter if in envelope Ex. HIV Ex. HIV

8 Viral Structure and Reproduction Two main modes of infection by viruses Two main modes of infection by viruses Virus binds to cell Virus binds to cell Tricks cell into taking in DNA Tricks cell into taking in DNA DNA either becomes copied or kills the cell DNA either becomes copied or kills the cell

9 Viral Structure and Reproduction Lytic Cycle – the viral replication process that rapidly kills a host cell. Viral DNA enters cell and takes over Turns on genes to make more viruses Viral enzymes break down the host cell membrane and new viruses released Lyses means to break apart

10 Viral Structure and Reproduction Lysogenic Cycle – type of replication in which a virus does not immediately kill a host cell Viral DNA combines with host DNA - prophage Prophage is copied during mitosis and passed on to daughter cell Two paths – remain a permanent part of the cell OR become lytic

11 Viral Diseases Defense against infectious disease Defense against infectious disease First defense – Skin Viruses can enter only through openings – nose, mouth, eyes, ears, etc. Once at the cell, the virus uses triggers to trick the cell in to allowing the virus in

12 Viral Diseases Viral Diseases Viral Diseases Common cold Common cold 200 different viruses 200 different viruses Mutates easily Mutates easily Influenza Influenza Prominent in winter Prominent in winter Easily spread – epidemic Easily spread – epidemic 3 subtypes infect humans 3 subtypes infect humans Highly mutatable – new vaccine each year Highly mutatable – new vaccine each year SARS – Severe Acute Respiratory Syndrome SARS – Severe Acute Respiratory Syndrome Recent viral infection Recent viral infection Similar to influenza Similar to influenza HIV HIV Retrovirus – uses RNA instead of DNA Retrovirus – uses RNA instead of DNA Lysogenic infection Lysogenic infection Becomes a lytic infection when active Becomes a lytic infection when active Infects WBC which leads to AIDS Infects WBC which leads to AIDS Highly mutatable Highly mutatable

13 Viral Diseases Vaccine Vaccine Preparation of a weakened or killed pathogen Preparation of a weakened or killed pathogen Prompts the body to form immunity Prompts the body to form immunity Ex. MMR, Chickenpox, Hepatitis, Menigitis Ex. MMR, Chickenpox, Hepatitis, Menigitis When the virus returns again, the body is prepared When the virus returns again, the body is prepared

14 Bacteria and Archaea Microorgansims are everywhere Microorgansims are everywhere Smallest are prokaryotes Range in size 1 – 5 micrometers There are roughly 1 billion types of bacteria and individual prokaryotes above, on, and in the earth’s surface

15 Bacteria and Archaea Identification of Prokaryotes Identification of Prokaryotes Shape Shape Chemical nature of cell wall Chemical nature of cell wall Movement Movement Obtaining of energy Obtaining of energy

16 Bacteria and Archaea Respiration Respiration Obligate aerobes - breathes oxygen Obligate anaerobes - does not breathe oxygen Facultative anaerobes – don’t need oxygen, but are not harmed by it

17 Bacteria and Archaea Structural Comparisons Structural Comparisons Archaea and bacteria appear very similiar Archaea and bacteria appear very similiar Cell walls, single celled Cell walls, single celled DNA is in the form of a plasmid DNA is in the form of a plasmid Some are non-motile Some are non-motile Others: Others: Whiplike movement with a flagellum or cillia Whiplike movement with a flagellum or cillia

18 Bacteria and Archaea Cell shape Cocci – spheres Bacilli – rods Spirilla – spirals Strepto – chains Staphylo – clusters

19 Bacteria and Archaea Cell shape Cocci – spheres Bacilli – rods Spirilla – spirals Strepto – chains Staphylo – clusters

20 Bacteria and Archaea Cell Shape Cell Shape Cocci – spheres Bacilli – rods Spirilla – spirals Strepto – chains Staphylo – clusters

21 Bacteria and Archaea Cell shape Cell shape Cocci – spheres Bacilli – rods Spirilla – spirals Strepto – chains Staphylo – clusters

22 Bacteria and Archaea Cell shape Cell shape Cocci – spheres Bacilli – rods Spirilla – spirals Strepto – chains Staphylo – clusters

23 Bacteria and Archaea Cell wall composition Gram positive – retain initial stain easily (violet) Gram negative – much thinner cell wall; doesn’t retain initial stain (pink)

24 Bacteria and Archaea Nutrition Heterotrophs - eat to obtain energy Chemoheterotrophs – must take in carbon Autotrophs - make their own food

25 Bacteria and Archaea Growth Growth Binary Fission – replicate DNA and divide Binary Fission – replicate DNA and divide Conjugation – exchange of genetic information through a pilli Conjugation – exchange of genetic information through a pilli Endospores – thick portion of cytoplasm enclosing the DNA Endospores – thick portion of cytoplasm enclosing the DNA

26 Beneficial Roles of Prokaryotes Prokayotes provide nutrients Prokayotes provide nutrients Key part of the digestive system of animals Decomposers Symbiosis - both members benefit (Ex. Plants and bacteria for nitrogen) Fermentation Diseases Lyme disease Cholera Tetanus Toxic Strep Prokaryote Roles in Ecosystems Prokaryote Roles in Ecosystems Cyanobacteria Produce much of the oxygen we breath Bioremediation Using bacteria to remove pollutants Ex. Oil spills, biodegradeable materials

27 Bacterial Diseases and Antibiotics Two ways bacteria infect Two ways bacteria infect Damage cells and tissue Release toxins throughout body

28 Bacterial Diseases and Antibiotics Mycobacterium Tuberculosis Mycobacterium Tuberculosis Destroys cells in the lungs Streptococcus and Clostiridium botulinum Streptococcus and Clostiridium botulinum Strep throat Food poisoning Corynebacterium diptheriae Corynebacterium diptheriae Diptheria

29 Bacterial Diseases and Antibiotics Antibiotics Antibiotics Block growth and reproduction of bacteria Block growth and reproduction of bacteria Major reason for increase in human expectancy Major reason for increase in human expectancy Also prime example of evolution Also prime example of evolution MRSA MRSA Evolution results from overuse, underuse, and misuse Evolution results from overuse, underuse, and misuse


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