MICROORGANISMS FRIEND AND FOE

1. MICROORGANISMS FRIEND AND FOE

2. Micro-organisms

3. What are micro-organisms? Micro-organisms are very tiny living things. They are so small that you need a microscope to see them. Viruses, bacteria and fungus are all types of micro-organism. Micro-organisms that cause diseases are often called germs. Micro-organisms are all around us, in the air, in our bodies and in water. Some micro-organisms are harmful to us, but others are helpful to us.

4. GOING DEEP INTO THE STUDY OF MICROORGANISMS • The study of microorganisms is know as Microbiology. • There are four types of microorganisms: 1) bacteria 2) algae 3) fungus 4) protozoa

5. Bacteria Bacteria, one-celled organisms visible only through a microscope. Bacteria live all around us and within us. The air is filled with bacteria, and they have even entered outer space in spacecraft. Bacteria live in the deepest parts of the ocean and deep within Earth. They are in the soil, in our food, and on plants and animals. Even our bodies are home to many different kinds of bacteria. Our lives are closely intertwined with theirs, and the health of our planet depends very much on their activities.

6. MORE ABOUT BACTERIA • Bacterial cells are so small that scientists measure them in units called micrometers (µm). One micrometer equals a millionth of a meter (0.0000001 m or about 0.000039 in), and an average bacterium is about one micrometer long. Hundreds of thousands of bacteria would fit on a rounded dot made by a pencil. • Bacteria lack a true nucleus, a feature that distinguishes them from plant and animal cells. In plants and animals the saclike nucleus carries genetic material in the form of deoxyribonucleic acid (DNA). Bacteria also have DNA but it floats within the cell, usually in a loop or coil. A tough but resilient protective shell surrounds the bacterial cell.

7. CONTD……………… • Biologists classify all life forms as either prokaryotes or eukaryotes. Prokaryotes are simple, single-celled organisms like bacteria. They lack a defined nucleus of the sort found in plant and animal cells. More complex organisms, including all plants and animals, whose cells have a nucleus, belong to the group called eukaryotes. The word prokaryote comes from Greek words meaning “before nucleus”; eukaryote comes from Greek words for “true nucleus.” The study of bacteria is called bacteriology, a branch of microbiology

8. NITORGEN FIXATION • Bacteria play a key role in making soil fertile. They convert nitrogen in Earth’s atmosphere into the nitrogen compound ammonia, which plants need to grow. Bacteria are the only organisms able to carry out this biochemical process known as nitrogen fixation. The bacteria able to fix atmospheric nitrogen usually live in association with plants, often integrated into the plant tissue. Bacteria in the genus Rhizobium, for example, form nodules (knobs) on the roots of beans and other plants in the legume family.

9. NITROGEN CYCLE

10. ALGAE • Algae, diverse group of simple, plant like organisms. Like plants, most algae use the energy of sunlight to make their own food, a process called photosynthesis. However, algae lack the roots, leaves, and other structures typical of true plants. Algae are the most important photosynthesizing organisms on Earth. They capture more of the sun’s energy and produce more oxygen (a by-product of photosynthesis) than all plants combined. Algae form the foundation of most aquatic food webs, which support an abundance of animals.

11. MORE ABOUT ALAGE • Algae vary greatly in size and grow in many diverse habitats. Microscopic algae, called phytoplankton, float or swim in lakes and oceans. Phytoplankton are so small that 1000 individuals could fit on the head of a pin (see Plankton). The largest forms of algae are seaweeds that stretch 100 m (300 ft) from the ocean bottom to the water’s surface. Although most algae grow in fresh water or seawater, they also grow on soil, trees, and animals, and even under or inside porous rocks, such as sandstone and limestone. Algae tolerate a wide range of temperatures and can be found growing in hot springs, on snow banks, or deep within polar ice.

12. FUNGI • Fungus, any member of a diverse group of organisms that—unlike plants and animals—obtain food by absorbing nutrients from an external source. The fossil record suggests that fungi were present 550 million years ago and may have evolved even earlier. Today thousands of different types of fungi grow on and absorb food from substances such as soil, wood, decaying organic matter, or living plants and other organisms. They range from tiny, single-celled organisms invisible to the naked eye to some of the largest living multicellular organisms. In Michigan for example, the underground portion of an individual Armillaria mushroom, a type of fungus, extends more than 12 hectares (30 acres). Other fungi are among the longest-lived organisms on Earth—some lichens, a living partnership of a fungus and an alga, are thought to be more than 4,500 years old.

13. MORE ABOUT FUNGI OR FUNGUS • Common fungi include mushrooms, puffballs, truffles, yeasts, and most mildews, as well as various plant and animal pathogens (disease agents), such as plant rusts and smuts. Some experts estimate that there are 1.5 million fungus species, of which approximately 100,000 have been identified. The unique characteristics of fungi led scientists to classify these important organisms into a separate kingdom, Kingdom Fungi (also known as Mycenae). Certain fungus-like organisms, such as downy mildews, water moulds (also known as oomycetes), and slime moulds, once classified as fungi, are now placed in the Kingdom Protista.

14. PROTOZOA • Protozoa, collective name for animal-like, single-celled organisms, some of which may form colonies. In the classification followed in this the protozoa are placed in the kingdom Protista with other single-celled organisms that have membrane-enclosed nuclei. Protozoa have little or no differentiation into tissue systems. Several phyla are commonly recognized. They include flagellated Zoomastigina, many species of which live as parasites in plants and animals; the amoeboid Sarcodina, which includes the Foraminifera and Radiolaria both important components of the plankton; ciliated Ciliophora, many with specialized structures suggesting the mouth and anus of higher organisms; Cnidosporidia, parasites of invertebrates, fish, and a few reptiles and amphibians; and Sporozoa, many species of which are parasites of animals (including humans). More than 20,000 species are known, including such familiar forms as paramecium and amoeba

15. MORE ABOUT PROTOZOA • Most species are found in such aquatic habitats as oceans, lakes, rivers, and ponds. They vary in length from 2 to 70 micrometers. Protozoa obtain their food by ingesting bacteria, waste products of other organisms, algae, or other protozoa. Most species are motile, either by whip like structures called flagella, hair like structures called cilia, or amoeboid motion, a streaming type of movement involving the formation of pseudo pods (foot like extensions).

16. VIRUS • Virus (life science), infectious agent found in virtually all life forms, including humans, animals, plants, fungi, and bacteria. Viruses consist of genetic material—either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA)—surrounded by a protective coating of protein, called a capsid, with or without an outer lipid envelope. Viruses are between 20 and 100 times smaller than bacteria and hence are too small to be seen by light microscopy. Viruses vary in size from the largest poxviruses of about 450 nanometres (about 0.000014 in) in length to the smallest polioviruses of about 30 nanometres (about 0.000001 in). Viruses are not considered free-living, since they cannot reproduce outside of a living cell; they have evolved to transmit their genetic information from one cell to another for the purpose of replication.