Bacteria and Viruses

And Infectious diseases


Microbe: is the oldest form of life on earth. They are only a single cell—millions of them can fit into the eye of a needle! Many microbes are good—they help us eat and breathe. But some can invade animals and people. They can make you sick. Bacteria and virus are types of microbe.

Bacteria: single celled organisms that can be good or bad. Our body fights off the bad ones. We use antibiotics to get rid of bad bacteria.

Virus: Very small and they cannot live one their own. They need to infect another organism and live in their cells.

DNA: stores the genetic/biological information about an organism

Antibiotic: types of medications that destroy or slow down the growth of bacteria

All organisms are composed of cells - the fundamental unit of life.

Most organisms are single cells; other organisms, including humans, are multicellular.


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What is the difference between a living and a non-living thing?

Living things have certain characteristics that distinguish them from non-living things.

  • living things are composed of one or more cells
  • they metabolize [produce and use energy]
  • they can grow
  • they can adapt to their environment
  • they can reproduce.

What are viruses really? Are they a life form? In what way do they seem alive?

They can certainly grow and reproduce, and they use genetic material found in other forms of life. They can adapt to their environment—for example, by developing resistance to certain drugs.

How do we catch viruses and infectious diseases?

We can catch them by passing these harmful bacteria and viruses from person to person or from animal to person.

3D medical animation - Virus infection - Virusinfektion - designidentity

Why do vaccines NOT protect against all viral diseases?

Vaccination is effective only against viruses with nonvarying proteins on their surfaces. If the surface proteins mutate of the new changes are not recognized by the immune system.

Examples of virus caused diseases

AIDS, dengue fever, measles, small pox, and bird flu

What are components/structure of virus?

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Flu Attack! How A Virus Invades Your Body
  • Viruses are made of genetic material (DNA or RNA) packaged in a protein shell.

  • They are very small (10 nm-3 microns in diameter)

  • They are commonly like the shape above but some viruses are enveloped with a membrane (outer layer protecting the structure)

  • Proteins have specific shapes. Repeating units of the same protein (or a set of proteins) can create a closed symmetric shape.

  • Viruses have limited space in their genome, so they use symmetry and multiple copies of one or a few types of subunits to create large shells.

  • Viruses inject their genetic material into host cells and hijack their cellular machinery for their own propagation. Viral infection can be prevented by blocking the entry of its genetic material into host cells.

Learning about the structure of viruses can help us better understand the disease that they cause, their prevention and treatment.

Summary about VIRUS

1. A virus is an infectious organism that reproduces within the cells of an infected host.

2. A virus is not alive until it enters the cells of a living plant or animal.

3. A virus contains genetic information wrapped in a protein coat.

4. Viruses can be useful as well as harmful.

5. A virus that mutates ensures its own survival by making itself unrecognizable to immune systems and vaccines.

6. Even viruses engineered for useful purposes can be harmful if unchecked.


Bacteria: The Good, The Bad, The Kinda Gross

How do bacteria live?

  • Bacteria (plural) are tiny, one-cell creatures that get nutrients from their environments in order to live. In some cases that environment is a human body.

  • Bacteria can reproduce outside of the body or within the body as they cause infections.

Are bacteria bad?

Not all bacteria are bad. Some bacteria are good for our bodies—they help keep things in balance. Good bacteria live in our intestines and help us use the nutrients in the food we eat and make waste from what's left over. We couldn't make the most of a healthy meal without these important helper germs! Some bacteria are also used by scientists in labs to produce medicines and vaccines (vak-SEENS).

Examples of bacterial infection

Some infections bacteria cause include sore throats, ear infections, cavities in your teeth.

What is the structure of bacteria?

  • DNA: genetic instructions

  • Cytoplasmic membrane: limits access to the cell’s interior

  • Cytoplasm: between the DNA and the membrane, where metabolic reactions occur

Bacteria also often have these features:

  • Cell wall: resists pressure

  • Flagella: movement

  • Pili: attachment

  • Capsule: protection

Virus vs. Bacteria

Bacteria and viruses - What is the difference between bacteria and viruses?

How are viruses different from bacteria?

Unlike bacteria, viruses lack the internal machinery that would allow them to metabolize and reproduce on their own. Instead, they hijack the host cell and use its metabolic processes to make more viruses. Outside of a host cell, a virus cannot function.

The Immune System Explained I – Bacteria Infection