M

MICROBES

An Introduction

Streptococcus bacteria

Microbes are microscopic organisms—too tiny to see without a microscope. They are abundant on Earth. They live everywhere—in air, soil, rock, and water. These microscopic organisms are found in plants, animals, the human body, and all around us.

What are microbes?Scientist=microbiologist

Not all microbes are harmful. Some microbes keep us healthy (digestive system), while others can make us sick. Microbes that make us sick are called infectious, pathogens, or disease causing agents.

http://www.infobarrel.com/Media/Bacteria_and_Virus

We know that microbes cause infectious diseases-diseases that can be spread. Near the end of the 20th century, researchers began to learn that microbes also contribute to many chronic diseases and illnesses. Mounting scientific evidence strongly links microbes to some forms of cancer, coronary artery disease, diabetes, multiple sclerosis, and chronic lung diseases.

Most microbes belong to one of four major groups: 1. bacteria 3. fungi 2. viruses 4. protozoa. A common word for microbes that cause disease is “germs.”

1 2 3 4

1. Cholera 2. Influenza (flu) 3. Mushroom 4. Euglena

Microbes belonging to the bacteria group are made up of only one cell. Under a microscope, bacteria look like balls (cocci), rods (bacilli), or spirals (spirilli). The shape of a bacterial cell helps scientists identify the type of bacteria. They can be a single bacteria or in chains or groups.

BACTERIAScientist = bacteriologist

cholera

Filamentous cyanobacterium

Borrelia burgdorferi

Bacteria are prokaryotic cells. Prokaryotes are a group of organisms that are usually unicellular. This cell does not have a nucleus, mitochondria or other membrane bound organelles. It does have DNA/hereditary material.

Some bacteria (aerobic bacteria) need oxygen to survive. Others (anaerobic bacteria) do not. Like all living cells, each bacterium requires food for energy and building materials. There are countless numbers of bacteria on Earth—most are harmless, and many are even beneficial to humans. There are two groups Eubacteria (on or around you) and Archaebacteria (ancient, unusual bacteria).

Less than 1 percent of bacteria cause diseases in humans. For example, harmless anaerobic bacteria, such as Lactobacilli acidophilus, live in our intestines, where they help digest food, destroy disease-causing microbes, fight cancer cells, and give the body needed vitamins. Healthy food products, such as yogurt, sauerkraut, and cheese, are made using bacteria.

Some bacteria, however, produce poisons called toxins, which can make us sick. For example, botulism, a severe form of food poisoning, affects the nerves and is caused by toxins from Clostridium botulinum bacteria (does not need oxygen to grow, closed cans/containers).

Viruses are the smallest microbes, much smaller even than bacteria. Viruses are not cells. They consist of one or more pieces of hereditary material (DNA/RNA) with a protein coat. Viruses can be rod-shaped, sphere-shaped, multisided or irregular shaped.

VIRUSES

Scientist =

Virologist

Cancer

H5N1 Avian flu

Small pox

Most viruses do cause disease, because they invade living cells (hosts). Once inside the cells, they take over the nucleus, insert DNA, and they multiply/produce more viruses. Viruses attack certain cells, tissues, organs, or species.

Warts H1N1 Swine Flu Adenovirus

When a virus comes in contact with a cell it likes, it attaches to the surface of that cell. Then, it injects hereditary material into the nucleus, taking over the nucleus. The virus can be active, using the nucleus to create more virus particles (kills the cell to release them).

14

Viruses must infect a host cell to reproduce.Viruses which cause the host to burst (Lyse) are

called Lytic viruses. Their cycle is as follows:1. Infection- by random contact activates the virus and

injects its genetic material (injects DNA into the host cell nucleus)

2. Growth -the viral genetic material takes over the translation process & viral material is produced (makes a copy of its DNA).

3. Reproduction- Thousands of copies of viral DNA & protein are made in a short time (makes copies of the its DNA & food).

4. Assembly- in the final stage of reproduction, viral DNA acts as a starting point for new viruses to be assembled (creates new viruses).

5. Destroys- destroys nucleus and cell to release viral copies

Viruses must infect a host cell to reproduce.Viruses which cause the host to burst (Lyse)

are called Lytic viruses. Their cycle is as follows:1. Infection- by random contact activates the virus

and injects its genetic material (injects DNA into the host cell nucleus)

2. Growth -the viral genetic material takes over the translation process & viral material is produced (makes a copy of its DNA).

3. Reproduction- Thousands of copies of viral DNA & protein are made in a short time (makes copies of the its DNA & food).

4. Assembly- in the final stage of reproduction, viral DNA acts as a starting point for new viruses to be assembled (creates new viruses).

5. Destroys- destroys nucleus and cell to release viral copies.

15

The virus can be latent, instead of active. The virus invades the nucleus and joins DNA with the cell’s DNA. It then hides in the nucleus being reproduced each time the cell makes a copy. When the virus is activated, it produces new viruses. Herpes Simplex 1 is a latent virus. This produces cold sores/fever blisters around the mouth and nose area.

Herpes simplex 1

A fungus is actually a primitive plant. Fungi can be found in air, in soil, on plants, and in water. Thousands, perhaps millions, of different types of fungi exist on Earth. The most familiar ones to us are mushrooms, yeast, mold, and mildew. Some live in the human body, usually without causing illness.

FUNGI

Scientist =

Mycologist

Fungal diseases are called mycoses. Mycoses can affect your skin, nails, body hair, and internal organs. Aspergillus fumigatus fungi, for example, can cause aspergillosis, a lung disease. Some fungi have made our lives easier. Penicillin (made from mold) and some antibiotics, which can kill harmful bacteria in our bodies, are made from fungi.

penicilliumaspergillosis

Other fungi, such as certain yeasts, can be helpful. For example, when a warm liquid, such as water, and a food source, such as sugar, are added to certain yeasts, the fungus ferments. The process of fermentation is essential for making healthy foods like some breads and cheeses.

Protozoa are a group of microscopic one-celled animals. Protozoa can be parasites or predators. In humans, protozoa usually cause disease.

PROTOZOA

Scientist =

protozoologist

amoeba

giardia

euglenaparameciumplasmodium

Some protozoa, like plankton, live in water environments and serve as food for marine animals, such as some kinds of whales. Protozoa also can be found on land in decaying matter and in soil, but they must have a moist environment to survive.

marine plankton protozoa in soil