Viruses, Bacteria, & Infectious Diseases

1. Viruses, Bacteria, & Infectious Diseases Learning Target Objectives: (I can …) Compare and contrast viruses to bacteria: their spread, our immune response, and the treatments used for each. Classify viruses and prokaryotes based on shape, gram-stain results, etc. describing bacterial and viral structure and reproduction. Evaluate the effects of bacteria on humans, good and bad. Predict the significance to health of the different stages of a viral or bacterial infection. Design a controlled experiment using bacteria. Research and identify illnesses/diseases and the organisms that cause them. Discuss the importance of the contributions made by scientists such as Jenner, Sabin, Salk, etc. to health/medicine. Explain the body’s immune response to illness.

2. Vocabulary: Capsid * reverse transcriptase * retrovirus * bacteriophage * lytic cycle * lysogenic cycle * Edward Jenner * Salk & Sabin * Louis Pasteur * monera * cocci * bacilli * spirilli (spirochete) * diplo- * strepto- * staphylo- * archaeo- * anaerobes * halophile * thermoacidophile * gram negative * gram positive * plasmids * endospores * saprophyte * parasite/pathogen * autotroph * obligate anaerobes * facultative anaerobes * obligate aerobes * binary fission * conjugation * pili * toxin * endotoxin * exotoxin * antibiotics * pathogen * Koch’s postulates * phagocytes * inflammatory response * neutrophils * macrophages * interferon * arthropods * antigen * lymphocytes * antibodies * immunity * vaccination * allergy * histamine * polio * AIDS * cyanophyta

3. Viruses • Not classified in any of the 5 kingdoms • Considered non-living because they cannot reproduce without a host’s help • Are sub-cellular agents made of nucleic acid (either RNA or DNA) surrounded by a protein “coat” Viral Structure: 1) a piece of nucleic acid 2) capsid – a protein coat which holds the nucleic acid No nucleus, no organelles. Must use a host’s organelles to make more viruses.

4. Viral Spread: Viruses cannot move on their own. They move by hitching a ride on dust and water droplets in the air. They can be spread through food, drink, saliva, blood, or other bodyfluids, as well as insect bites. Viral Invasion: 1) Virus attaches to host cell. 2) Viral nucleic acids are injected into host cell. Capsid remains outside of cell. 3) Viral nucleic acid “turns off” host cell processes and redirects the cell to make new viral nucleic acid and capsids. 4) Viral components join togather 5) Host cell, bursts releasing viruses.

5. DNA Viruses: 1) May link to host DNA and then make RNA, then protein, etc. as needed. OR 2) May start making its own RNA that will direct ribosomes to make viral protein. RNA Viruses: 1) The viral RNA may direct protein synthesis directly. (Ex: polio virus) OR 2) The RNA may be transcribed in reverse using reverse transcriptase to make DNA. The DNA makes new RNA which then directs viral protein synthesis. This type of virus is called a retrovirus. (Ex: AIDS virus)

6. Bacteriophage – virus that invades bacteria. Many bacteria are NOT (as) harmful until infected with viruses that use the bacteria to make toxins. Ex: diphtheria bacteria and scarlet fever – when streptococci bacteria are invaded. Viral Cycles (Stages): Lytic cycle – virus replicates in host, then breaks it open, spreading viruses to new cells. Lysogenic cycle – virus invades host cell, may join with the DNA but remains inactive (dormant) unless “irritated”. Common Viral Disorders: Papillomavirus (warts) Herpes viruses (chicken pox, shingles, mononucleosis) Herpes Simplex (cold sores, STD) Smallpox Rabies Polio Flu or Adenovirus Encephalitis Epstein-Barr (mono – it affects B-cells) Measles AIDS (affects T-cells) Mumps Cancer?

7. Because viruses live inside our own cells, they are difficult to kill without killing our cells too. Some treatments include: AZT (AIDS) Acyclovir (a.k.a Zovirax or Valtrex – prevents viral replication) Interferon (one of our bodies natural responses) Vaccination (prevention rather than treatment) “fever” Important Scientists: Edward Jenner – used vaccine made from cowpox to prevent smallpox Salk and Sabin - polio vaccines (affected Pres. Franklin Roosevelt) Louis Pasteur – rabies vaccine

8. Bacteria Kingdom: Monera • Prokaryotes (no membrane bound organelles or nucleus) • Single-celled • Microscopic 3 general shapes of bacteria: 1) spherical (cocci) 2) rod-shaped (bacilli) 3) spiral (spirilli or spirochetes) Prefixes for bacterial colonies: Diplo – in pairs Strepto – in chains Staphylo – clusters (like grapes) All 3 shapes can exist as single cells.

9. Kingdom Monera: 4 Phyla: 1) Phylum Archaebacteria: Archaeo – ancient These live in harsh, primitive environments where most other organisms could NOT survive. a)methanogens – live in some digestive tracts, at the bottom of bogs, and in sewage treatment ponds. They use CO2 and H2 to form methane (CH4) and water. They are anaerobes – live only in areas where free oxygen is not found. b)extremehalophiles – phile- “lovong” halite – salt Salt loving bacteria live in high salt areas such as the Great Salt Lake and the Dead Sea.

10. c)thermoacidophiles – thermo – heat Live in very hot, acidic areas such as the hot springs of Yellowstone National Park or in other volcanic areas. 2)Phylum Schizophyta: Contains 4 classes which can be further classified by their reaction to Gram stain (crystal violet). a)Gram-negative bacteria – have a protective (peptoglycan) layer which resists taking on a full stain (stain pink). * HARD to kill with antibiotics. b)Gram positive bacteria – don’t have the protective coating. They take on crystal violet stain (stain purple). Can be killed fairly easily with antibiotics. --- ---- ---- ---- ---- ---- This phylum has bacteria which cause: diptheria, tuberculosis, typhus, syphillis, Lyme’s disease,. But some also produce antibiotics.

11. 3)Phylum Cyanophyta: • Also called blue-green bacteria • Autotrophs, contain chlorophyll & other pigments but no chloroplasts. The Red Sea got its name from occasional large populations of red pigmented bacteria (blooms). • Often confused with algae • Some found in soil will form nodules in legume (peas, beans, etc) roots to “fix” nitrogen. 4)Phylum Prochlorophyta: • Live with saltwater organisms. (Some consider this a sub-group of cyanophyta but these may only contain chlorophyll, no other pigments.)

12. Moneran (bacterial) Structure & Movement • Single chromosome of DNA in a circular shape • May have plasmids (smaller, separate circular DNA pieces) • Have cell walls • Some produce protective capsules around their wall (gram-negative bacteria) • May produce endopsores – an envelope that allows the bacteria to become dormant and resist heat, cold, chemicals, etc. until a better environment returns. • May move by flagella or filaments Nutrition: Heterotrophs: 1) Saprophytes – feeds on dead or decaying matter (Help recycle nutrients) 2) Parasites/pathogens – absorb nutrients from a host, may result in disease. Autotrophs: 1) photoautotrophs- use sunlight to make food, 2) chemoautotrophs – use chemical energy to make food

13. Bacterial Respiration: Obligate anaerobes – can not survive in environment with oxygen (Ex: methanogens) Facultative anaerobes – can live with OR without oxygen Obligate aerobes – require oxygen (Ex: bacteria that infect the lung, like tuberculosis) Reproduction: • Can divide about every 15 minutes • Binary fission – asexual, splitting into two. • Conjugation – a piece of DNA from one bacteria is transferred to another across a pili bridge. This DNA is then incorporated into the new bacteria’s existing strand or as a separate plasmid.

14. Toxin Production: Toxin – a poison Endotoxin – in cell walls of gram-negative bacteria. Cause fever, weakness, etc. Exotoxin – bacterial wastes secreted out. VERY potent. Ex: tetanus exotoxin, diphtheria, botulism. Many bacteria only begin producing certain toxins if infected by a virus (bacteriophage) ---- ---- ---- ---- ---- ---- ---- Antibiotics – chemicals produced by microorganisms that inhibit growth of or kill other microorganisms.

15. Some Bacterial Diseases: Rickettsia – spread by ticks & lice, causes Rocky Mountain Spotted fever. Lyme disease – spread by deer ticks (possibly other ticks). Can cause paralysis, etc. Botulism – deadly food poisoning (double vision is a symptom) Gonorrhea – sexually transmitted disease. Strep throat/scarlet fever/rheumatic fever – caused by Streptococcus pyogenes (Note:There are many different strep strains out there.) Impetigo – usually staphylococcus 9sometimes strep) Plague (Black Death, Bubonic plague) – spread by rat fleas Tetanus – causes “lockjaw” Cholera – spread through water usually Syphillis – STD Control Bacterial Spread by: Heating, drying, preservatives (dehydrate bacteria), freezing (SLOWS growth & reproduction but doesn’t kill bacteria), antibiotics (but these also kill the good bacteria

16. Infectious Diseases Pathogen – any agent that causes an infectious disease (a disease that can be spread from 1 host to another). Pathogen Exs: bacteria, invertebrates (such as worms). Identifying Pathogens: Koch’s Postulates are used to identify a pathogen. 1) isolate the suspected organism from its host 2) grow the organism in pure culture in the lab 3) inject the lab grown organism into a healthy host 4) wait to see if the same disease appears. If it does, you’ve found the pathogen. Some pathogens produce toxins (harmful chemicals). One of the most damaging types are neurotoxins. These attack nerve cells and prevent transmission of nerve impulses. (Ex: botulism – produces a neurotoxin which causes double vision and possibly death)

17. Beneficial Bacteria ***(put list on back of your note outline packet) Used to produce: Vinegar, Yogurt, Sauerkraut, Pickles, Cheeses, Vitamin K – made by bacteria in our intestines, used for normal blood clotting Insulin – human DNA is inserted in bacteria. The bacteria “read” the human gene and produce insulin. Antibiotics – many are produced by bacteria or other microorganisms.

18. Disease Transmission(spread): Microorganisms can be spread from host to host by: air, water, direct contact, and arthropods (crayfish, spiders, insects, ticks, etc.) The microorganisms may be transmitted in dormant form as a spore or a cyst. This protects the organism from damage or death until it finds a host. Immune Response: Our reaction to foreign substances. Nonspecific Defenses: 1) skin, mucous membranes, etc. (our first line of defense) prevent pathogens from entering the body. Tears, sweat, saliva, and urine contain chemicals that kill some pathogens. 2) Pathogens that get into our body, past our first line of defense, can start an infection. This causes an inflammatory response (swelling, warmth, fever, redness, pain) which brings white blood cells (WBCs) to the area.

19. WBCs involved in the inflammatory response include 2 types of phagocytes (Phagocytosis = cell eating by engulfing particles): 1) neutrophils – small WBCs that surround and eat small numbers of bacteria. 2) macrophages – large WBCs that ingest large numbers of bacteria. (***Note: There are many other types of WBCs.) A nonspecific immune response to a viral infection involves the production of a protein known as interferon. Interferon prevents viruses from reproducing. Genetic engineering has helped increase the production of interferon. Interferon is also being studied as a cancer fighting agent and is used to treat AIDS (however, it’s not a cure.)

20. Specific Immune Defenses: Specific pathogens can be recognized by our immune system. Antigen – usually proteins found on or produced by pathogens which cause our immune system to react in a specific way. Lymphocytes – special WBCs including B-cells (attacked by mono) and T-cells (attacked by AIDS) T-cells : (differentiate/mature in the thymus gland) attack antigens directly by joining with the pathogen. There are several T-cell types including memory cells which recognize antigens that have attacked before. Usually memory cells can kill the pathogen before symptoms arise for the second time. B-cells : (differentiate/mature in the bone marrow) produce antibodies (Y-shaped proteins that bind to and destroy antigens.)

21. Immunity and Immune Disorders: Immunity – resistance to a specific pathogen. Vaccination – exposure to a “killed” or “weakened” (attenuated) virus/pathogen, given as an injection. This usually gives the person immunity to this pathogen. Antibiotics – drugs that fight bacterial infections. Ex: Penicillin (discovered by Sir Alexander Fleming. It is produced by a mold. Note: don’t confuse antibiotics with antibodies which are bodies make. Allergy – an immune response to a harmless (non-pathogen) antigen. The response may include the release of histamine, a chemical that causes watery eyes, runny nose, etc. in an attempt to flush out the antigen.

22. AIDS Acquired Immune Deficiency Syndrome • caused by HIV (human immunodeficiency virus) • This is a retrovirus • Transmitted through sexual contact, contaminated syringes, infected blood • Enters T-cells and are unaffected by antibodies • May remain in a lysogenic state for 10 years or so before becoming lytic. (This destroys the T-cell leaving the person susceptible to other illnesses.)