Viruses!

Viruses are microscopic particles that invade the cells of plant, animals, fungi, and bacteria.

Bacteriaphage AIDS Virus

Comparison of structures

of viruses and animal

cells.

1. A virus is not a cell. A typical virus is composed of a core of genetic material surrounded by a protein coat. The protein coat protects the virus and enables it to invade its host cell.

2. In many viruses, DNA is the genetic material. Other viruses have RNA.

3. Viruses are parasitic and can reproduce only inside the cells of their host. This makes viruses very different from bacteria and protists.

AIDS Virus

Viral genetic material has room for only a few genes. Usually they are only genes that code for the protein coat and for

enzymes that enable to virus to take over the cell.

There has been an ongoing debate among scientists as to whether or not viruses are alive or not alive. Viruses lack three essential features of living things:1. They are not made of cells2. They cannot make proteins by themselves3. They cannot use energy

•Even though viruses can reproduce they are only able to so when inside living cells. because they cannot reproduce on their own most scientists classify them as non - living things.

Virus: Living or Not?

Virus Reproduction

All viruses reproduce by taking over the reproductive machinery of a cell.

How Viruses Work Video(2:25)

In the Lysogenic Cycle:

1. Viral DNA merges with Cell DNA and does not destroy the cell.

2. The Virus does not produce progeny. 3. There are no symptoms of viral infection. 4. Temperate viral replication takes place.

Differences Between Lytic

and Lysogenic CyclesIn the Lytic Cycle:

1. Viral DNA destroys Cell DNA, takes over cell functions and destroys the cell.

2. The Virus replicates and produces progeny phages. 3. There are symptoms of viral infection. 4. Virulant viral infection takes place.

Virus Reproduction

The reason HIV is such a dangerous virus is because it has the ability to take over the

white blood cells!

HIV waits for a white blood cell to attack it, then it takes over the white blood cell and

makes it into a virus making factory.

The effect of this is that other viruses can now take over your body and kill you because your

defenses have been taken down

by the HIV.

Vaccines Video

(3:22)

The most effect defenses we have against viral diseases is vaccination.

Viruses cause serious human diseases in addition to AIDS, such as measles and influenza.

Viral diseases are much more difficult to treat than bacterial diseases. This is true for a few reasons.

#1 most antibiotics that are used on bacteria disrupt the bacteria’s cell wall or proteins inside the bacteria.

Since a virus has no cell wall or inner proteins it is immune to those medicines.

#2 since viruses actually enter healthy cells, it is hard to find them.

Not only is it difficult to find them but it is hard to kill them without also killing the cells they are living in.

Herpeshttp://www.contemporarypediatrics.com/contpeds/article/articleDetail.jsp?id=108010

BacteriaUnderstanding Bacteria VIDEO

(4:00 min)

Although you do not see them, bacteria are everywhere and affect your life in many

ways.

large intestine: bacteria synthesize (make) vitamin K, which is essential to good nutrition

your mouth: may cause cavities in your teeth

diseases: cholera, typhus, pneumonia, sexually transmitted diseases, and tuberculosis

KeyCocci – roundBacilli – rodSpirilli – spiralStrepto – chainsStaphylo – clustersDiplo - pairs

prefix

Most species of bacteria are one of 3 different shapes:

Ex. streptococci

Ex. Bacillus anthracis

Ex. Treponema pallidum = syphilis

Spiral (called spirilli)Ex. Treponema pallidum = syphilis

Gram StainingA series of dyes is added to a sample of bacteria

as a microscope slide is being prepared during the process of gram staining.

Bacteria are either Gram-positive or Gram-negative.

The difference between Gram-negative and Gram-positive bacteria is important in diagnosing and treating

diseases caused by bacteria.

Bacteria such as Streptococcus pneumoniae stain purple during Gram staining and are known as

Gram-positive bacteria.

Bacteria such as E. coli stain pink during Gram staining and are known as Gram-negative bacteria.

Then the bacterium splits into two identical cells. Each cell receives one molecule of DNA and some cytoplasm.

Bacteria do not undergo mitosis or meiosis. Instead,

the bacterium first duplicates its DNA

so that there is enough DNA for

two cells.

Bacteria Reproduce Rapidly

Some bacteria are able to divide as many as 5 times in one hour.

If you were to place a single bacterium into a culture dish containing an

abundant (lots) supply of food, you could find more than 600,000 bacteria in

the dish after only 4 hours.

After 6 hours, the bacterial population of the dish could reach 476 million!

4,096 – 8,192 – 16,384 – 32,768 – 65,536 – 131,072

- 8,388,608 - 4,194,304 - 2,097,152 - 1,048,576 - 524,288 - 262,144 -16,7

77,2

16 –

33,

554,

432

– 67

,108

,864

– 1

34,2

17,7

281 -2 – 4 – 8 – 16 – 32 – 64 – 128 – 256 – 512 – 1,024 – 2048 -

Sometimes bacteria do have a form of sex called conjugation.

One bacterium reaches out to another using a thread-like structure

called a pilus.

The first bacterium transfers part of its DNA to the other bacterium through the pilus. By this exchange, bacteria can quickly create or pass along new traits

that help them adapt to different environments.

How Bacteria Obtain Nutrition

A major reason for the success of bacteria is the wide variety of foods they can use.

Example:

A glass of milk left out of the refrigerator provides a wealth

of food for bacteria. Within hours, bacteria

colonize the milk and break down its supply of sugar,

causing the milk to curdle.

•Some bacteria are autotrophs. •Autotrophic organisms make their own food by using simple molecules.

Autotrophs and Heterotrophs

•Most bacteria cannot make their own food and are therefore heterotrophs. •Many feed on dead animals and animal wastes; dead plants; and fallen leaves, branches, and fruit.

Helpful Bacteria

• Fix nitrogen

• Recycle nutrients

• Used to make certain foods and

aid in digestion– yogurt, olives, sauerkraut, pickles

• Clean up oil and toxic spills - video (.19)

• Used to make antibiotics, vitamins, and drugs

• Used as natural pesticides

Bacteria Are Fighting Back

Until the late 1980s, many scientists thought that we had conquered most infectious bacterial

diseases and that the rest would soon be controlled.

But, bacteria reproduce rapidly and mutate. And, they become

resistant to the drugs we use against them.

Fight Back video (2.30)