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Viruses, Bacteria Diversity of Life Today… • Viruses • Prokaryotes • • • VIRUSES Viruses are non-living organisms. Technically they are not considered living organisms, since they cannot self replicate (they’re not a kingdom) Remember that living organisms: 1. 2. 3. 4. 5. 6. 7. 8. Organized (have cells) Maintain homeostasis Take energy & use it Respond to stimuli Grow & develop Able to self reproduce (sexually or asexually) Have Genetic material Adapt to their environments Virus structure • Viruses: Just a protein coat for protection (capsid) and a nucleic acid (RNA or DNA) for information on how to make more copies of the same virus • Cannot replicate/reproduce on its own! Needs a host… Virus is a cellular parasite • Uses cell machinery of a host cell to replicate and to produce more viruses • They come in many varieties, sizes & shapes Viruses cause diseases • Viruses cause numerous diseases in Plants, animals, bacteria & fungi… • Examples of human viruses: • Herpes virus • Hepatitis virus • Rabies • Ebola – emerging epidemics • Influenza (“flu”) – respiratory infection (fever, headache, chills, cough, stuffy nose, sore throat) caused by a variety of viruses. Flu season: Nov. – March. • Passed on by sneezing, coughing – air, hand-to-mouth, etc. • Vaccine helps prevent outbreaks. Human Viruses • Human Immunodeficiency Virus (HIV) – causes AIDS. • Transmitted through sexual contact, sharing infected needles, blood transfusions, mother to baby. • Severe Acute Respiratory Syndrome (SARS) – brand new deadly virus, started in China, causes atypical pneumonia. Spreads quickly. • Antibiotics Don’t Work but some do have antiviral medication. Plant Viruses • Tobacco Mosaic Virus (TMV) causes mottling symptoms • Rose mosaic virus • Spots on fruit • Wheat stunt virus Genetic Reassortment in Influenza Viruses Generation of Novel Influenza A Viruses Human H2N2 ANTIGENIC SHIFT Genetic Reassortment Avian H3N8 Point mutation of HA and NA genes ANTIGENIC DRIFT Human H3N2 Virus-induced tumours Virus Infection [ ] Uninfected Cell Uncontrolled cell growth and tumour formation Infected cell PROKARYOTES • Bacteria are small and unicellular • They have no internal organelles (no chloroplasts, nucleus, ER, mitochondria) Bacteria • Replication is asexual – clonal, rapid simple division (no mitosis) • Pseudo-sexual reproduction, has means for Genetic exchange • Called conjugation Bacteria • Bacterial forms: cocci, bacilli, spirilli • Some forms are photosynthetic: cyanobacteria Bacterial pathogens • Animal pathogens: • Typhoid, tuberculosis • Bubonic plague or “Black Death”, transmitted by fleas (caused 25 million deaths in Medieval Europe) • Syphilis, gonorrea (venereal diseases) • E. coli, Salmonella (food poisoning) 76 million illnesses worldwide Some examples of contagious bacterial diseases are: -strep throat -impetigo -pertussis (whooping cough) -bacterial conjunctivitis (pink eye) Antibiotics Work Bacterial control • There are ways of controlling bacterial growth: • Disinfectants • Antibiotics • Low temperatures • High temperatures, • Low oxygen Beneficial Bacteria • Nitrogen-fixation – convert atmospheric N into useful Nitrogen (N gas plants animals) • Decomposition in the biosphere – get rid of dead organisms, nature’s recyclers • Intestinal Bacteria – supply vitamins (K) • Commercial use: yogurt, sour cream, fermentation • Genetically-engineered bacteria produce insulin and other important chemicals. • Can also help clean up oil spills: oil ‘eating’ bacteria! What are Antibiotics? Powerful medicines with one very important job: to fight disease-causing bacteria. When used properly, antibiotics can save lives. 5 Antibiotic Resistant Bacteria Are: Bacteria that mutate and are able to resist the antibiotics that are meant to kill them. This is a normal process speeded up by the overuse and misuse of antibiotics. 8 What is Antibiotic Misuse? • Taking antibiotics when they are not needed: – for viral infections • When needed, taking antibiotics incorrectly: – stopping the medicine when you feel better - not finishing the prescription – saving antibiotics for a future illness – sharing or using someone else’s medicine 6 Why is Antibiotic Misuse a Problem? 1. Antibiotics become less effective and may not work the next time you use them. 2. Improper use of antibiotics leads to more antibiotic resistant bacteria. 3. Antibiotic resistant bacteria can be spread throughout the community and from person to person. 7 Antibiotic Resistant Bacteria • Require stronger antibiotics • Are more common in people who recently used antibiotics* • Can be spread within a family or a community • Can affect anyone • Are becoming more common 9 Emergence of Antimicrobial Resistance Susceptible Bacteria Resistant Bacteria Resistance Gene Transfer New Resistant Bacteria Selection for AntimicrobialResistant Strains Resistant Strains Rare Antimicrobial Exposure Resistant Strains Dominant This process shows what? Can Disease affect a population or evolution? Can Disease affect a population or evolution? 1. Small pox introduction to Native Americans 2. Sickle- Cell anemia advantages to being heterozygous Populations decrease with pathogens. What if a few are resistant to disease? How do we fight them? • Sanitation and safe water • Antiviral- kill/suppress viruses Our Immune System • First line of defense: skin, tears, stomach acid • Second line of defense: Inflammation – white blood cells, temp. increases (fever not so bad!) Antigens and Antibodies • Antigen – is the substance that triggers a response: pollen, bacterial toxin, virus • Antibodies – Proteins that recognize and bind to antigens (shaped like the letter Y) – Produced by B cells – Travel through the blood – Can “remember” antigens Vaccines: Vaccine helps prevent outbreaks. •Our bodies use introduced antigens to make antibodies to fight the disease in the future. •What are advantages to this? Passive Immunity: Receive antibiodies from mother (birth or breast milk) Active Immunity: You make antibodies on your own from getting sick or vaccine