Structure and Function of Viruses and Bacteria

Viruses & Bacteria 1

UNIT GOALS • Students will derive the relationship between single-celled and multi-celled organisms and the increasing complexity of systems. • B) Compare how structures and function vary between the six kingdoms. • C) Examine the evolutionary basis of modern classification systems. • d) Compare and contrast viruses with living organisms.

A virus is a nonliving particle with a simple structure.Composed of a nucleic acid (DNA or RNA) surrounded by a protein coat. Virus that infects bacteria 2

Virus Structure • Capsid- The capsid is the protein shell that encloses the nucleic acid; Three functions: • 1) it protects the nucleic acid from digestion by enzymes, • 2) contains special sites on its surface that allow the virus to attach to a host cell, and • 3) Allow virus nucleic acid penetrate the host cell’s membrane and, in some cases, to inject the infectious nucleic acid into the cell's cytoplasm. • Envelope - Surrounds the capsid. Composed of two lipid layers interspersed with protein molecules Or RNA Or RNA 3

Viral Nucleic Acid • The nucleic acid of each virus encodes the genetic information for the synthesis of all proteins. • Only a few groups of viruses use DNA. • Most viruses maintain all their genetic information with the single-stranded RNA. 5

Viruses, such as the influenza virus, that have RNA as their genetic material mutate more often that DNA viruses. 6

Animation Lytic Cycle • The virus attaches to a host cell and injects its nucleic acid into the cell. • The viral nucleic acid is immediately replicated, eventually causing the host cell to burst, releasing new viral particles. • These new viruses then attack other cells. 7

Lysogenic Cycle Animation • After the virus embeds its nucleic acid into the chromosome of the host cell, the viral nucleic acid is replicated along with the host cell’s DNA. • Then the virus becomes dormant, sometimes for years without the host knowing. • The virus may suddenly become active, resuming the lytic cycle, which will eventually destroy the host cell. 8

Overview: Lytic and Lysogenic cycles 9

Are viruses alive? Do they meet the criteria for life? • Can They: • Reproduce? • Obtain and use energy? • Grow, develop, and die? • Respond to the environment? 11

Vaccines • Made from parts of a virus. • Then when our bodies see the virus again it recognizes and fights the virus. • Antibiotics do not work on viruses! • Most vaccines contain purified fragments taken from killed bacteria or viruses. • Some vaccines contain live viruses, but in a very weak form that dos not cause disease. stimulates the body’s immune response "teach" the immune system how to recognize and fight bacteria and viruses Clip on next slide 13

EXTRAS • Prion-is a type of infectious agent made only of protein. • Chronic wasting disease, (in deer and elk), mad cow disease • All of these diseases affect the structure of the brain or other neural tissue, and all are untreatable and fatal. 16

Viroids • small naked single-stranded RNA molecules that infect plant cells and cause disease. • Smaller than viruses, viroids are not enclosed in a protein coat of any kind. • They generally consist of less than 400 nucleotides and do not contain any genes. 17

Compare and contrast viruses with living organisms. Examples to include: -Mode of nutrition? -Characteristics of living things -Reproduction -Structure -Homeostasis? - Cell structures? Viruses 6 kingdoms of Living things

Diseases Caused by Viruses • Smallpox • Ebola • Hantavirus • Herpes • Lassa Fever • Mononucleosis • West Nile • Yellow fever • Cancer • Influenza • Measles • Chickenpox • Polio • HIV • Mumps • Rabies • Hepatitis • Common cold

Influenza contagious respiratory illness 1918 pandemic 20 to 40 million people More people died of influenza in a single year than in four-years of the Black Death Bubonic Plague from 1347 to 1351. Known as "Spanish Flu" or "La Grippe" the influenza of 1918-1919 was a global disaster

What's the Future of Polio?Through intensive vaccination programs, a coalition of organizations in 1999 decided to work toward world eradication of polio by 2005. Between 1988 and 1998, wild-type polio was eliminated from North America, South America, and Europe. But polio still exists in Africa, as well as India and some of its neighboring countries. Polio • Polio is a contagious, historically devastating disease that was virtually eliminated from the Western hemisphere in the second half of the twentieth century. Although polio has plagued humans since ancient times, its most extensive outbreak occurred in the first half of the 1900s before the vaccination, created by Jonas Salk, became widely available in 1955. • People who have abortive polio or nonparalytic polio usually make a full recovery. However, paralytic polio, as its name implies, causes muscle paralysis - and can even result in death. In paralytic polio, the virus leaves the intestinal tract and enters the bloodstream, attacking the nerves (in abortive or asymptomatic polio, the virus usually just stays in the intestinal tract). The virus may affect the nerves governing the muscles in the limbs and the muscles necessary for breathing, causing respiratory difficulty and paralysis of the arms and legs. Although the acute illness usually lasts less than 2 weeks, damage to the nerves could last a lifetime. Clip

Ebola Virus The onset of illness is abrupt and is characterized by fever, headache, joint and muscle aches, sore throat, and weakness, followed by diarrhea, vomiting, and stomach pain. A rash, red eyes, hiccups and internal and external bleeding may be seen in some patients. native to the African continent. People can be exposed to Ebola virus from direct contact with the blood and/or secretions of an infected person: contact with objects, such as needles, that have been contaminated with infected secretions

Human Immunodeficiency Virus HIV attacks some of the cells that are vital to a healthy immune system, including the white blood cells known as T-helper cells or CD4 cells. AIDS means 'acquired immune deficiency syndrome'. It is a condition that sets in when the HIV virus has killed so many T-helper cells that the immune system is no longer able to recognize and react to attacks from everyday infections.

single-stranded RNA virus and is animal-borne. Lassa Fever The Mastomys rodents shed the virus in urine and droppings. Lassa fever may also spread through person-to-person contact. This type of transmission occurs when a person comes into contact with virus in the blood, tissue, secretions, or excretions of an individual infected with the Lassa virus. Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. These include fever, retrosternal pain (pain behind the chest wall), sore throat, back pain, cough, abdominal pain, vomiting, diarrhea, conjunctivitis, facial swelling, proteinuria (protein in the urine), and mucosal bleeding. The most common complication of Lassa fever is deafness. 1% of infections with result in death. The number of Lassa virus infections per year in West Africa is estimated at 100,000 to 300,000, with approximately 5,000 deaths. In some areas of Sierra Leone and Liberia, it is known that 10%-16% of people admitted to hospitals have Lassa fever, which indicates the serious impact of the disease on the population of this region. West Africa

Chickenpox • Chickenpox is a very contagious viral disease that causes an itchy outbreak of skin blisters. • The chickenpox virus spreads from person to person by direct contact with fluid from broken chickenpox blisters. • Chickenpox is usually a mild disease. However, in adults and children with weakened immune systems, chickenpox can cause serious complications and even death. • A vaccine is now available to prevent chickenpox.

Hantavirus A person may be exposed to hantavirus by inhaling dust after disturbing nests or breathing in closed spaces inhabited by infected mice. The deer mouse (Peromyscus maniculatus) is the main carrier of hantavirus; however, other wild rodents can cause problems as well. The first symptoms are fever, chills, muscle aches, and sometimes nausea, vomiting, and abdominal pain. The muscle aches are often severe, and occur in the thighs, hips, back and sometimes the shoulder. Some patients will develop coughing and shortness of breath within a few days. Others may go for as long as a week with the other symptoms before developing a cough and shortness of breath, followed by the abrupt onset of respiratory distress, often severe and fatal. Mortality is about 40 to 50 percent

Measles • Diseases of childhood that causes a skin rash. • Serious complications, such as pneumonia, croup or encephalitis, can occur. • The disease starts with a cold, fever, cough, conjunctivitis (red eye) and fatigue. Three days later, a red blotchy rash starts on the face - then spreads to the rest of the body, including the feet. The fever starts to go down on the second or third day of the rash. There may be some fine peeling of the skin after the rash fades. Most patients are ill for about seven days; • IS IT CONTAGIOUS?VERY. It is most common in late winter and early spring. Most people have been exposed to the disease 10-12 days before they have any symptoms. Spread by coming in contact with the saliva of someone who has the disease through coughing, kissing or sharing of eating utensils. • Once you have had a case of measles you have lifetime immunity (protection) to the disease.

Mumps Mumps is an infectious disease that causes swelling of the saliva-producing glands near the ears. Can last 7-10 days The most common symptom is painful swelling in front of and below the ears. Often, there is pain when eating or moving the jaw. Some people have headaches, loss of appetite, fever and a tired feeling about a day before the swelling. One side of the face usually swells before the other. In males past puberty, a problem that is associated with mumps is orchitis (swelling of the testicles). Mumps is spread by contact with the saliva of someone who has the disease. It is contagious until all the swelling is gone. Mumps occurs year-round, but is more common in the winter and spring.

Rabies • Infects the central nervous system, causing encephalopathy and ultimately death. Early symptoms in humans are nonspecific, consisting of fever & headache. • As the disease progresses, neurological symptoms appear and may include insomnia, anxiety, confusion, slight or partial paralysis, excitation, hallucinations, agitation, hypersalivation, difficulty swallowing, and hydrophobia. Death usually occurs within days of the onset of symptoms. The principal rabies hosts today are wild carnivores and bats.. Rabies immune globulin and five doses of vaccine given over a 4-week period typically RNA virus. Most often transmitted through the bite of a rabid animal

Smallpox • Infection usually occurred by inhalation of virus • acute, with fever, malaise, headaches, and backaches. The initial toxemia phase lasted 4-5 days. On about the third or fourth day, the characteristic rash appeared. First, it appeared on the buccal and pharyngeal mucosa, the face, and the forearms. Within a day, it spread to the trunk and lower limbs. • The lesions usually protruded from the skin and are firm to touch. About 8 weeks after onset of the rash, the lesions dried up and became crusted by day 14. By the end of the third week, most crusts had fallen off, with the exception of the palms and the soles. The outcome of infection was either death or recovery with immunity. In 1966, the World Health Organization started a program for the worldwide eradication of smallpox. Through intensive case finding and vaccination of direct and indirect contacts, the disease was finally eradicated on December 9,1979.

Hepatitis C Before a blood test was discovered in 1989 to screen for HCV, this was the most frequent hepatitis to be acquired from blood transfusions and blood products. Up to half of those with chronic disease will go on to develop liver failure and need a transplant. Each year, 8,000 to 10,000 people die in the United States because of hepatitis C-related cirrhosis or HCV-related liver cancer. Hepatitis Hepatitis A mainly transmitted by contaminated food and water. Hepatitis is a disease that impairs liver function either temporarily or permanently, sometimes even leading to death. It can be initiated by a host of factors, but primarily by viruses. Drugs also can cause hepatitis but when the specific drug is discontinued, the liver usually returns to normal. Hepatitis B This type is essentially a blood-borne virus with other bodily fluids being infectious, notably semen and saliva, and is often transmitted from mother to fetus.

Herpes • Infection caused by the Herpes Simplex Virus (HSV), which resides in the nerve ganglia after the initial exposure to the virus. • Because the virus is so effective at "hiding out" in the nerve cells, the body is never able to eliminate the herpes virus completely. Instead, after the initial infection, the body produces antibodies which show up in the blood stream. • Blood tests which indicates the presence or lack of these antibodies. • The antibodies make it easier for the body to recognize and attack the virus when it re-emerges from the nerve cells in the form of an outbreak. • For this reason, out breaks following the primary outbreak usually diminish in frequency and intensity over time. • Some people may never have another outbreak.

Retrovirus • Has an RNA genome that is converted to DNA in the host cell • HIV • Reverse transcription ANIMATION

Structure and Function of Viruses and Bacteria