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Viruses and Prokaryotes Chapter 20 pages 572 - 599

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Estimated number of viruses on the planet is 10 31 ! If you stacked them up you would make a tower that would stretch beyond our galaxy and its neighbors. Every time you get sick with the flu the number of viruses in your body rises to 100 trillion in a few days. The slide shows viral abundance in the oceans

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Virus a non-living particle made primarily of proteins and nucleic acids. They can reproduce only by infecting cells. Bacteriophage attacks bacteria Influenza virus

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Lytic infection viral DNA enters cell, makes copies of itself and causes the cell to burst (lyse) Lysogenic infection viral DNA becomes part of host DNA (prophage) and may not become active for many generations

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Shingles is a viral disease caused by the virus that causes chicken pox. After recovery from chicken pox the virus lies dormant in the cells, sometimes for years, before causing its next disease, Shingles.

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Chicken pox highly contagious viral disease. Causes raw pockmarks that heal. The disease is uncommon now with the advent of the vaccine.

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Common cold is a viral disease of the upper respiratory tract. It is a retrovirus in that it contains RNA, not DNA. The host cells ribosomes translate the viral RNA into capsid and other viral proteins. Within 8 hours the host cell releases hundreds of new viruses to attack other cells.

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HIV is a retrovirus that causes AIDS. When this virus infects a cell it makes a DNA copy of its RNA which is inserted into the host cell DNA. Like a prophage it may not activate for a while. When it does it programs the cell to produce viral proteins and RNA.

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Helper T cells, when activated by dendritic cells stimulate B cells to produce antibodies that bind to a specific foreign protein.

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The HIV virus attacks T4 helper cells. These are white blood cells that help acitivate other immune cells when the body is attacked by disease. HIV infection sequence

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Prokaryotes are either Archaea or Eubacteria. Eubacteria are the larger of the two domains.

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Comparison of Eukarya, Eubacteria and Archaea

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Eubacteria cell structure. Gram negative bacteria do not stain well and are more resistant to antibiotics. Gram negative bacteriaGram positive with negative

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Archaebacteria cell structure is more similar to Eukaryotes than to Eubacteria. Archaebacteria lack peptidoglycan in their cell wall.

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Bacteria are classified according to cell shape.

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Bacterial colony shapes.

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Various bacteria colony shapes and colors

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Hallophile bacteria colonies. Pink color is the dominant trait. Needs extremely salty environment to live.

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How organisms get energy

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Heterotroph Take in organic molecules from the environment or other organisms to use as both energy and carbon supply. This is a low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped

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Photoheterotrophs use light for energy, but cannot use CO 2 as a source for carbon. Microscopic view of the bacterium Rhodobacter sphaeroides, a formaldehyde-ingesting organism which can be used to clean up contaminated groundwater

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Photoautotrophs Use light energy to convert CO 2 into carbon compounds. This is a picture of Anabena, a common filamentous cyanobacterium that also fixes nitrogen.

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Chemoautotrophs use energy released by chemical reactions involving ammonia, hydrogen sulfide, sulfur, ferrous iron and hydrogen. Bacteria living near this undersea black smoker can breakdown some of the chemicals to get energy.

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Binary Fission A form of asexual reproduction. Under favorable conditions bacteria can reproduce every 20 min.

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Endospore formation in poor conditions many bacteria can form an endospore. These spores have a tough outer coat that resists stains. The spores can exist for years and come alive when conditions are favorable for growth.

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Bacterial conjugation a hollow bridge forms between two cells and and exchange of genetic material, a plasmid, occurs. This results in a cell with a different genetic genotype.

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Obligate aerobe bacteria. These bacteria need oxygen to survive. An example would be Mycobacterium tuberculosis: the bacterium that causes tuberculosis in human beings.

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Tuberculosis bacteria attack the lungs. It is spread through coughing and sneezing. Most infections do not have symptoms. One in ten progress to active disease which kills 50% of those untreated.

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Tuberculosis can cause extensive scarring in the lungs

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Known from antiquity, there was some success in treating tuberculosis by placing people in sanatoriums, where they could get fresh air and good food.

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Tuberculosis has been treated with a combination of drugs for over 50 years. A challenge is getting people to complete their treatment after they start feeling better.

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Henry David Thoreau died of tuberculosis or consumption as it is sometimes called.

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Nelson Mandela

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Ringo Starr

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Obligate anaerobe. These bacteria die in the presence of oxygen. they live deep in the soil, animal intestines or airtight containers. An example is Clostridium botulinum; the bacterium that causes botulism

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A nerve toxin that the bacterium emits is what causes botulism. One of the initial symptoms is droopy eyelids.

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Injections of botulinum toxin type A can remove wrinkles for up to 4 months.

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Facultative anaerobe this type of bacteria can survive without oxygen when necessary. Esherichia Coli lives anerobically in sewage and anaerobically in human intestines.

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Bacteria are essential in the decomposition of of organic matter. In this way they return needed raw materials back into the environment. They are especially useful in the decomposition of sewage.

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A compost pile is a way that people use bacteria to decompose organic material

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Producers photosynthetic bacteria are important producers. The cyanobacterium Prochlorococcus is probably the most abundant photosynthetic organism on the planet.

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Prochlorococcus distribution.

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Anabena fresh water cyanobacteria the heterocysts are cells that specialize in nitrogen fixation. Akinetes are spore-like cells that function in reproduction

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Nitrogen fixation. Nitrogen is needed to make proteins and other molecules. Only a few prokaryotes can convert N 2 into useful forms. The process involves turning N 2 into ammonia and the ammonia into nitrates that plants can use or attached to amino acids that all organisms can use

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Disease causing bacteria (pathogens) cause disease by destroying living cells or by releasing chemicals that upset homeostasis. The slide below shows a person with strep throat.

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Releasing Toxins Some bacteria cause disease because of a particular deadly toxin they release. Diptheria is an upper respiratory illness caused by a bacterium that releases a toxin

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Meningococcal disease the bacteria attack the lining of the brain and the endotoxin they produce can affect the heart and rupture blood vessels.

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A person with meningococcal disease. Even with prompt antibiotic treatment 10% of infected people die. It is not unusual for patients to lose hands and feet to this disease.

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The endotoxins rupturing of blood vessels can result in amputation. Even when antibiotics are used early about 10% of the cases will be fatal.

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Controlling bacteria Washing hands and surfaces with soap. Soap does not kill the bacteria but it is washed away.

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Disinfectants Chemical solutions (bleach, ammonia, hydrogen peroxide) can be used to to clean surfaces. Hydrogen peroxide destroys bacterial cell membranes.

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Food storage refrigeration, canning, pickling, salting, dehydration can make it difficult for bacteria to grow

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Sterilization by heat. Objects can be sterilized when placed boiling water

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Vaccines A vaccine is a heat killed pathogen or part of a pathogen. The body responds to the presence of the foreign protein by making antibodies against the heat killed pathogen. If a live pathogen shows up the antibodies are already there and the pathogen is defeated before it has a chance to start.

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Polio Vaccine Developed by Dr. Jonas Salk in 1952. This vaccine effectively ended the incidence of polio in the US.

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A small percentage of people who contracted polio would become paralyzed as the virus attacked the motor nerves. These patients are in iron lungs as their chest muscles have become paralyzed.

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Franklin D. Roosevelt contracted polio as a young man. He was loathe to let the public see him in a wheel chair. This one of the few photos that exist of him sitting in a wheel chair

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Jack Nicklaus had polio as a young boy. Fortunately it did not cause any paralysis. Only.5% of people infected would develop a paralytic symptoms. But among millions infected this ended up to be a lot of people.

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Sister Kenny a self taught Australian nurse developed a physical therapy for polio victims that greatly reduced their chances of becoming paralyzed. She founded and ran the Sister Kenny institute for many years.

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Viral diseases do not respond to antibiotics, but some can be prevented with vaccines. There are some new medications out that attack specific viral enzymes that host cells do not have.

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Campaign to eradicate Polio. Global effort begun in 1988 by WHO World Health Organization. Cases have been reduced by 99.9% (From hundreds of thousands to 291 in 2012). This child is getting the oral vaccine which contains a weakened virus.

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The annual flu vaccine is filled with antigens for three or four influenza strains. Most of the time this vaccine causes the body to produce the right antibodies to prevent these viruses from infecting the body.

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There are several diseases that have appeared in the past 35 years. Because there is little history of infection for people our bodies are not well prepared to produce the antibodies to defeat these pathogens

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SARS (Severe Acute Respiratory Syndrome) was found to be a virus that had jumped from civets to humans. When a disease is able to infect a new species that species often has trouble defending itself

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Antibiotic resistance tests; the bacteria in the culture on the left are sensitive to the antibiotics contained in the white paper discs. The bacteria on the right are resistant to most of the antibiotics.

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The misuse and overuse of antibiotics allows those bacterial organisms lots of generations to develop immune strains. The accepted practice of giving antibiotics to all livestock is one example.

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Over time antibiotics are less effective. There are fewer new ones being developed because the research is not funded well.

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Bird Flu a viral disease that initially infected chickens and evolved to infect humans. First case in 2003 in china. It is transmitted from infected birds to people and does not seem to go from person to person yet

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Spanish Flu outbreak of 1918. The first of two H1N1 influenza pandemics the second in 2009. 500 million people affected and 50 to 100 million died. US troops fighting in WWI contracted the disease and died at home. The disease killed up to 20% of the people infected and about 5% of the worlds population died.

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A prion is an infectious agent that is a misfolded protein. When this protein touches a normal cell protein the normal cell protein is transformed into the disease causing misfolded protein.

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Stanley Prusiner coined the term prion (protein infectious agent), to describe the proteins he found in sheep afflicted with scrapie (1972). He was strongly criticized for his work, but ended up with the Nobel prize in medicine in 1997.

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Scrappie is a fatal, degenerative disease that affects the nervous system of sheep and goats. It is related to BSE (bovine spongiform encephalopathy) or mad cow disease and chronic wasting disease. This slide shows samples of brain tissue and compare scrapie with KURU and CJD other spongiform brain diseases

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Mad Cow disease is BSE in humans. Cattle were getting the disease through protein additives in their feed and humans would get the disease by eating hamburger that included protein from the brain and spinal cord. This disease first struck Great Britain in 1988.

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Chronic Wasting disease. This is BSE in deer, moose and elk. Both Minnesota and Wisconsin have periodically required hunters to have their deer checked for CWD. In 2012 Minnesota required this from an area where captive deer where found with CWD

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To date, no strong evidence exists that CWD can be passed on to humans. Many people strongly encourage others to not include nervous tissue in the preparation of hamburger or sausage as that is where the prions are located. This map shows CWD, by county, in 2013