Bacteria And Viruses Inside this Issue:

Volume 1, Issue 2

Newsletter 2011

By Professor Dante Joa, CHI

What bacteria do?

2

How does it help cows?

2

Antibiotics

2

Viral Morphology

2

Fixing Nitrogen in soil

2

VIRUSES

3

Are viruses even alive?!?!

3

TYPES OF VIRUSES

3

Smaller than viruses

4

Influenza Serology 4 and Epidemiology

Complications of influenza

5

Treatment and Control

5

ORTHOMYXO VIRUS

5

Bacteria Basics.- They are alive! Bacteria are the simplest of creatures that are considered alive. Bacteria are everywhere. They are in the bread you eat, the soil that plants grow in, and even inside of you. They are very simple cells that fall under the heading prokaryotic. That word means they do not have an organized nucleus. Bacteria are small single cells whose whole purpose in life is to replicate. Okay. So we've told you they don't have an organized nu-

cleus. True. They do have DNA. It is grouped in an area called the nucleoid. They have cell membranes like other cells and even a protective cell wall. Mind you, their cell wall is not like the one in a plant. It's a special kind that bacteria have for protection. They don't have any organelles, just ribosomes. (These are all characteristics of prokaryotes if you remember.)

What do they look like? Very, very small. You might have seen pictures of some bacteria. Since we don't know what you have seen, we'll tell you there are three basic shapes. Spherical bacteria are in the shape of little spheres or balls. They usually

form chains of cells like a row of circles. Rod shaped bacteria are look like the E. coli living in your intestine. You can imagine a bunch of bacteria that look like hot dogs. They can make chains like a set of linked sausages.

Spiral shaped bacteria twist a little. Think about balloon animals for these shapes. It's like a balloon animal in the shape of a corkscrew.

Bacteria

Human Bacteria

Fixing Nitrogen in soil There are bacteria that go through a process called fixing nitrogen. These bacteria, living in the roots of plants, actually help them absorb nitrogen from the surrounding soil. The nitrogen is very important for the growth of the plant, and these little bacteria give them an advantage for survival. Nitrogen -fixing bacteria protect soybeans

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What do bacteria do? All sorts of things. Sorry to be so vague, but they do just about everything. Some help plants absorb nitrogen (N) from the soil. Some cause diseases like botulism. Some bacteria even live inside the stomachs of cows to help them break down cellulose. Cows on their own can digest grass and plants about as well as we do. They don't get many nutrients out of the

plants and can't break down the cellulose. With those super bacteria, the cellulose can be broken down into sugars and then release all of the energy they need. Imagine if scientists could develop bacteria to live inside of us that would break down plants. That would be something. We could eat grass and leaves all day long.

Helping cows eat grass As we said, not all protists are bad for the world. In the bacteria section we already told you about a species that lives in the digestive system in cows. These bacteria help cows break down the cellulose in plants. Similar bacteria live in all sorts of grazing animals, helping them survive off plant material. Many ecosystems are based on

ANTIBIOTICS Scientists have even discovered fungi that will help you battle bacterial diseases. So you get sick, the doctor looks at you and says you have a bacterial infection, maybe bronchitis. He prescribes an antibiotic to help you get better. Antibiotics are drugs designed to destroy bacteria by weakening their cell walls. When the bacterial cell walls are weak, your immune cells can go in and destroy the bacteria. Although there are many types now, one of the first antibiotics was called penicillin. It was developed from a fungus (a fungus named Penicillium found on an orange, to be exact).

Viral Morphology They say we learn best by doing, so let’s study viral structure by making a virus, starting from the nucleic acid inside and proceeding to the capsid and envelope. Virus are classified as either

DNA or RNA viruses. So we have two choices for our virus: DNA or RNA . of course nothing is quite that simple. The nucleic strands can be single-stranded, double stranded, linear, or looped,

in separated segments or one continuous strand. The nucleic acid sequences can encode a simple message or encode hundreds of enzymes and structural proteins.

Volume 1, Issue 2

Page 3

VIRUSES

Viruses Have these unique characteristics:

1. They are energy –less. They float around until they come in contact with an appropriate cell. 2. They are basic life forms composed of a protein coat, called a capsid, that surrounds genetic material. 3. Viruses do not have organelles or ribosomes. Certain viruses are futher enclosed by an external lipid bilayer membrane that surrounds the capsid and may contain glycoproteins. Some viruses also carry some structural proteins and enzymes inside their capsid. 4. The genetic material is either Dna or RNA. Never both!! The genetic material contains instructions to make millions of clones of the original virus. 5. Replication of the genetic material occurs when the virus takes control of the host cell’s synthetic machinery. Viruses contain all of the genetic information, but no the enzymes, needed to build millions of replicas of the original virus

TYPES OF VIRUSES As you go on to study more biology, you'll see many virus types. There are three basic shapes. 1) First there are helical virions. They are set up like a tube. The protein coat winds up like a garden hose around the core. 2) Next comes the polyhedral

shape. This shape group includes the classic virus shape that looks like a dodecahedron. A dodecahedron is a geometric shape with twelve (12) sides. These viruses have many facets and a seemingly hard shell of capsomeres (pieces of a capsid). There is a variation of the polyhedral

called globular. Globular shapes are basically polyhedral virions inside of a spherical (like a ball) envelope. 3) Last is the complex virus shape. You may have seen this one in books with the geometric head and long legs.

Are viruses even alive?!?! We're starting with the smallest of the small here. Some scientists argue that viruses are not even living things. We suppose it's easier to give you a list of what they can't do as opposed to what they can. What viruses can't do: (1) They can't reproduce on their own. They need to infect or invade a host cell. That host cell will do all the work to duplicate the virus. (2) They don't respond to anything. You can poke them or set up barriers, it doesn't matter. They either function or they are

destroyed. (3) They don't really have any working parts. While there some advanced viruses that seem fancy, viruses don't have any of the parts you would normally think of when you think of a cell. They have no nuclei, mitochondria, or ribosomes. Some viruses do not even have cytoplasm. We've already established what viruses aren't. Let's talk about what they are. Every virus has a few basic parts. The most important part is a small piece of

DNA or RNA (never both). That strand of nucleic acid is considered the core of the virus. The second big part is a protein coat to protect the nucleic acid. That coat is called the capsid. The capsid protects the core but also helps the virus infect new cells. Some viruses have another coat or shell called the envelope. The envelope is made of lipids and proteins in the way a regular cell membrane is structured. The envelope can help a virus get into systems unnoticed and help them invade new host cells.

Smaller than viruses

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There are things out there even smaller than viruses. The two that scientists have discovered are called prions and viroids. A prion is (as far as we know) just a protein. Prions are proteins that can invade cells and somehow direct their own duplication, making more of the isolated proteins. Viroids are a little different in that they are just RNA. Scientists have even discovered that they are responsible for some diseases.

Influ en Viroi za ds

Influenza Serology and Epidemiology Major mutational changes usually result in altered codon reading frames and a nonviable virus. Q: We all think that this is a pesky but mild self-limiting disease. It can cause pneumonia and more serious disease in the elderly, but usually it resolves without complications in 3 to 7 days. So why When looking at the disease have there been devastating influenza, 2 questions about pandemics of influenza epidemiology arise: throughout history, as in 1918? Over a few weeks in Q: If an antibody to the NA 1918,548,452 persons in the and HA are protective, why U.S., 12.5 million persons in do we continually get epiIndia, and 20 million persons demics of the bothersome worldwide died from this viflu, with fever chills, myalrus. gias, arthralgias, headache, A: Antigenic Shift: Now we are really shifting gears. We and other miseries. are taking the boat menA: Antigenic Drift: During vi- tioned above and airlifting it ral replication mutations can to a mountain in the Himalaoccur in the HA or NA, lead- yas. With antigenic shift ing to changes in the antithere is a complete change of genic nature of these glycothe HA, NA or both. This can proteins. This is termed anti- only occur with influenza genic drift because the type A because the mechachanges are small, just a lit- nism involves the trading of tle drift of the sailboat in the RNA segments between aniwater. The resulting new mal and human strains. strains are only partially atWhen 2 influenza types cotacked by our immune sysinfect the same cell, undergo tem, resulting in milder dis- replication and capsid packease in adults who have pre- aging, RNA segments can be viously acquired antibodies. mispackaged into another viThere are 3 types of influenza virus: A, B, and C. These types have many strains separated by antigenic differences in HA and NA. Type A infects humans, other mammals (swine, etc.), and birds. Type B and C have only been isolated from humans.

Swine Flu Virus

rus. This virus now wields a new HA or NA glycoprotein that has never been exposed to a human immune system anywhere on the planet. So the entire human population would be susceptible, leading to devastating pandemics. The new HA and NA antigens are given number subscripts to differentiate them. The pandemic of 1889 was caused by a virus with an H2 hemagglutinin, the pandemic of 1900 was caused by a new virus with H3 hemagglutinin; in 1918 a swine flu virus transferred its HA to a human virus and so was called Hswine hemagglutinin (HSW). The chart below is only included to demonstrate the many pandemics and their new HA and NA antigenic composition. 1989 H2N2 1900 H3N2 1918 HswN1 1947 H1N1 1957 H2N2* 1968 H3N2* 1977 H1N1* *Notice also that some strains can cause a second pandemic as a new unexposed population grows to adulthood.

Complications of influenza Even the normal yearly flu can cause complications. The elderly and immunocompromised suffer more serious illness as the virus spreads to the lower respiratory tract, resulting in pneumonia. The viral infection also lowers the host defenses against many bacteria. Secondary bacterial pneumonias by Staphylococcus aureus, Streptococcus pneumoniae, and others are common and the physician must follow patients (especially the elderly) closely until complete resolution of their illness. New fevers or failure to improve means danger!!

Treatment and Control Influenza viruses are grown in mass quantities in chick embryos, which are then inactivated, purified, and used as vaccines. Scientists carefully choose 3 strains that are circulating in the population or expected to cause an outbreak in the next season. These vaccines have variable success depending on the accuracy of the “guesswork”. The vaccines should be given to the elderly, immunocompromised patients, and health care workers. A drug called amantadine prevents the uncoating of influenza A. This medication can prevent infection if given daily before exposure, or it can decrease the severity of the illness if given early in the course.

ORTHOMYXO VIRUS Morphology 1. Negative (-) singlestranded RNA 2. Segmented (7-8) 3. Lipid containing envelope 4. Helical symmetry 5. Replicates in the nucleus! (Retroviruses are the only other type of RNA viruses that replicate in the nucleus) Virulence Factors 1. Hemagglutinin (HA) glycoprotein: binds tored blood cells. Also binds to receptors on cells of the upper respiratory tract, resulting in dumping of viral RNA into these cells.

2. Neuraminidase (NA) glycoprotein: breaks down neuraminic acid, an important component of mucin Clinical The Flu: Fever, runny nose, cough, myalgias, arthralgias, etc. *Complications 1. Secondary bacterial pneumoniasin the elderly 2. Reyes Syndrome in children who use aspirin; get liver and brain disease. Treatment & Prevention 1. Vaccine 2. Amantadine:

Prevents uncoating of influenza type A. Miscellaneous 1. Antigenic drift: small mutations resulting in minor changes in the antigenicity of HA or NA . This results in epidemics of the common flu 2. Antigenic shift (only occurs with influenza type A): reassortment Major changes of the HA or NA (including acquisition of animal HA or NA). This results in devastating influenza pandemics

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