Microorganisms Online Test 8th Science Lesson 6 Questions in English

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Microorganisms are too small in size that they cannot be seen through naked eye. These organisms can be seen only with the help of a microscope, they are also known as microbes. The science that deals with the study of microorganisms is known as microbiology

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Microorganisms occur everywhere. They are found in air, water (ponds, lakes, rivers and oceans), soil and even inside our bodies.

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Some of Microorganisms can even survive in severely adverse conditions, such as hot springs, deserts, snow and deep oceans. They remain inactive under unfavourable conditions and become active during favourable conditions.

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Microorganisms can be studied under five categories. They are:

 Virus

 Bacteria

 Fungi

 Algae

 Protozoa

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A virus is a tiny, particle made up of genetic material and protein. They are intermediate between living and non-living things. Virus means ‘poison’ in Latin. Viruses are intracellular obligatory parasites.

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Viruses are 10,000 times smaller than bacteria. Viruses have different shapes. They can be rod shaped, spherical or of other shapes.

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A virus contains a core DNA or RNA. Surrounding that core is a protein coat. The study of virus is called ‘virology’.

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In some viruses, the protein coat is covered by an envelope made of proteins, lipids, and carbohydrates. The envelope has spikes that help the virus particles attach to the host cells.

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Living characters of virus:

 They respond to heat, chemicals and radiations.

 They reproduce inside the host cells and produce copies of themselves.

 They show irritability.

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 They are inactive when present freely in the environment.

 They can be crystallized and stored for a very long time, like other non-living things.

 The metabolic machinery, cytoplasm is absent.

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Bacteria are single-celled prokaryotes (cells without nuclei). Cells with nucleus are called as Eukaryotes.

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Bacteria are considered to be the first living organisms on earth. The study of Bacteria is called Bacteriology.

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Bacteria are grouped under the kingdom Monera. The size of bacteria ranges from 1µm to 5µm (micro-meter).

Bacteria are of two types based on respiration

• Aerobic bacteria (requires oxygen).

• Anaerobic bacteria (Does not requires oxygen).

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Protein synthesis in bacteria is carried out by 70S ribosomes. A bacterium has an outer covering known as the cell wall. Nuclear material is represented by a nucleoid without nuclear membrane.

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Other cell organelles such as mitochondria, Golgi body endoplasmic reticulum etc., are absent in bacteria. Flagella aids in locomotion.

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Bacteria are described according to the shape of their cells. They are:

 Bacilli – Rod shaped bacteria. Eg. Bacillus anthracis

 Spirilla – Spiral shaped bacteria. Eg. Helicobacter pylori

 Cocci – Spherical or ball shaped bacteria. They can stick together in pairs (diplococcus)

 Vibrio – comma shaped bacteria. Eg. Vibrio cholera.

Explanation

Bacteria are also classified according to the number and arrangement of flagella, which are as follows:

 Monotrichous – Single flagella at one end. Eg. Vibrio cholera

 Lophotrichous – Tuft of flagella at one end. Eg. Pseudomonas.

 Amphitrichous – Tuft of flagella at both ends. Eg. Rhodospirillum rubrum.

 Peritrichous – Flagella all around. Eg. E. coli.

 Atrichous – Without any flagella. Eg. Corynebacterium diptherae

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Bacteria get their food in many ways. Photosynthetic bacteria make their own food. (Eg. Cyanobacteria)

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Some bacteria exhibit symbiotic relationship (eg. E.coli lives in the intestine of man). Bacteria reproduces by fission (binary and multiple fission).

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Fungi are group of eukaryotic organisms that lack chlorophyll. They grow in dark environments . There are around 70,000 species of fungi, living in the world.

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Fungi may be either unicellular (eg. Yeast) or multicellular (eg. Penicillium). They are found in all kinds of habitats.

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The study of fungi is called mycology. Fungi are included under kingdom Fungi. Some fungi are macroscopic (eg. Mushroom).

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Yeasts are found freely in the atmosphere. Yeast grows in all kinds of media containing sugar. The cell is ovoid in shape, containing cell wall and a nucleus.

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Yeast aids in fermentation with the help of the enzyme zymase. Yeast respires anaerobically. Yeast reproduces by budding.

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Mushrooms are found growing on wet soil in shaded places during the rainy season, such as at the roots of the trees. The umbrella shaped structure that grows above the soil is known as the fruiting body. There are small slit like structures under the umbrella which are known as gills. The gills contain spores.

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Walls of the hyphae are made up of chitin and cellulose. Hyphae help in transport of nutrients for the growth of mushroom.

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Reproduction in mushroom is by the method of fragmentation and spore formation. Walls of the hyphae are made up of chitin and cellulose.

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The mycelium is located underneath the fruiting body, in the top layer of the soil. Mycelium in turn is made up of thread-like structures called hyphae.

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Fungi are either saprophytes (i.e., derives nutrition from the remains of dead and decomposing plants and animals) eg. Rhizopus, Penicillium, Agaricus, or parasites (ie. derives nutrition from the living cells of the host) eg. Puccina, Albugo, Ustilago, or symbionts (i.e., fungus in the roots of vascular plant) eg. Mycorrhiza.

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Algae are very simple plant like eukaryotic organisms. Algae are found in moist habitats. Algae are rich in chlorophyll and can be seen as thin film on the surface of lakes and ponds, therefore they are known as ‘grass of water’.

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Algae are autotrophic and manufacture their own food with the help of chloroplast. Chloroplast contain chlorophyll (green) pigments for photosynthesis. The study of algae is called algology (phycology).

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Chlamydomonas is a simple, unicellular, motile fresh-water algae. They are oval, spherical or pyriform in shape. The pyriform (pear shape) is a common one found in ponds, ditches and water tanks. They have a narrow anterior end and a broad posterior end.

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Some algae have other photosynthetic pigments like fucoxanthin (brown), xanthophylls (yellow), phycoerythrin (red), phycocyanin (blue).

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A protozoan (in Greek protos = first and zoon = animal) is a single-celled eukaryote. They are included under the kingdom Protista.

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The study of protozoa is called Protozoology. They are found in ponds, ocean, in moist soil, and in the cells and tissues of plants and animals causing diseases.

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Protozoa range from 2-200 microns. Protozoans have specialized organelles. These organelles are used for movement, feeding, and other functions.

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 Ciliates – presence of cilia for locomotion (e.g. Paramecium)

 Flagellates – presence of flagella for locomotion (e.g. Euglena)

 Pseudopods – presence of pseudopodia for locomotion (e.g. Amoeba)

 Sporozoans – parasites (e.g. Plasmodium)

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Amoeba is a unicellular microscopic organism. It is found in ponds. Amoeba is irregular in shape. It has cell membrane, cytoplasm and nucleus.

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Amoeba is a protozoan that move by means of pseudopodia (in Latin, “false feet.”) Pseudopodia are the extended part of cell membrane. It helps to catch its prey (algae).

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Amoeba reproduces by means of fission and sporulation. The body ‘flows’ around the food particle and engulfs it forming food vacuoles. Contractile vacuoles are seen in the cytoplasm that help in excretion.

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The word ‘Anti’ means ‘against’. Antibiotic is a substance produced by living organisms which is toxic for other organisms. Sir Alexander Fleming was the first person to discover the antibiotic Penicillin in the year 1928.

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Alexander Fleming was the first person to discover the antibiotic Penicillin in the year 1928. The antibiotic Penicillin was obtained from the fungi Penicillium chrysogenum. It is used to treat diseases such as tetanus, diphtheria.

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Antibiotic Streptomycin is obtained from Streptomyces bacteria to cure various bacterial infections eg. Plague.

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Scientists discovered a new antibiotic pseudouridimycin. The new antibiotic is produced by a microbe found in a soil sample collected in Italy. The new antibiotic kills drug-sensitive and drug- resistant bacteria in a test tube and cures bacterial infections in mice.

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Vaccines are prepared from dead or weakened microbes. When the vaccine is injected to the body of a patient, the body produces antibodies to fight against the germs.

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Edward Jenner was the first person to discover small pox vaccine. He coined the term vaccination. vaccination is otherwise called as immunization.

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MMR vaccine for Measles, Mumps, Rubella. BCG (Bacille Calmette Guerin) vaccine for Tuberculosis.

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Microorganisms are called as decomposers because they act upon degradable wastes. During the process, nitrates and other inorganic nutrients are released into the soil, making the soil fertile. This compost is called as natural fertilizer.

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Rhizobium bacteria living in the root nodules of leguminous plants enrich the soil by fixing the atmospheric nitrogen as nitrates which are essential for the growth of plants. Some free-living bacteria in soil, cyanobacteria Nostoc can also fix nitrogen biologically.

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Microbes are used to protect the crops from pests. For example,

 Bacillus thuringiensis (Bt cotton) helps to control insects

 Trichoderma (Fungi) helps to protect roots and control plant pathogens

 Baculoviruses (Virus) attack insects and other arthropods.

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Aerobic microbes are allowed to grow in the primary effluent during the secondary stage of waste water treatment. These microbes consume the major part of the organic matter in the effluent eg. Nitrobacter sps. In the anaerobic treatment of sewage Methano-bacterium is used.

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Human and animal faecal matter and plant wastes are broken down by anaerobic bacteria to produce methane (biogas) along with carbon dioxide and hydrogen. These bacteria are called as methanogens.

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Alcoholic drinks are prepared by fermentation process using yeast. Sugars in grapes are fermented by using yeast. Beer is produced by the fermentation of sugars in rice and barley.

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Flax plants are tied in bundles and kept in water. Bacteria loosen the supporting fibres of the stem by acting on the stem tissues. This process is known as retting. Linen thread is made from these fibres eg. Pseudomonas aeruginosa.

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In Tanning industry bacteria act upon the skin of animals and makes it soft and therefore it becomes pliable

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Chlorella (green algae) is rich in proteins and vitamins is added to the dough which enrich the bread with nutrients.

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Yeast is used in bakeries to make bread and cakes. They are added to the dough to produce carbon dioxide which makes the dough rise. Bread and cakes are soft due to carbon dioxide gas.

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Lactose in the milk gets turned into Lactic acid by the action of Lactobacillus (bacteria). Therefore, the milk becomes thick (curd). It gives the sour taste. When curd is processed cottage cheese (panner) is obtained.

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Lactobacillus acidophilus that lives in the human intestine helps in digestion of food and fight against harmful disease-causing organisms. E. coli bacteria in human intestine help in synthesizing vitamin K and vitamin B complex

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Lactobacillus acidophilus are acid-loving bacteria. These are found in buttermilk, yogurt, sour cream, and frozen desserts. They convert sugar and carbohydrates into lactic acid, and hence are called “lactic acid bacteria.

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A few microorganisms are harmful to humans, animals and plants. They cause diseases and hence they are called as pathogens. Pathogens enter into the body through cuts and wounds in the skin, mouth or nose and cause diseases. Viruses causing ‘flu’ are spread through air.

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African sleeping sickness, which is spread by the bite of the tsetse fly, is caused by the flagellate protozoan Trypanosoma.

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For food processing, commonly used microorganisms are yeast, bacteria, and moulds. Fermentation process which is carried out by microorganisms results in the production of organic acids, alcohol and esters.

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Pickling is a method of preserving food in an edible antimicrobial liquid.

Fermentationis the microbial conversion of starch and sugars into alcohol. It makes foods more nutritious and palatable.

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Sugar is used to preserve fruits in an antimicrobial syrup with fruit such as apples, pears, peaches, plums or in a crystallized form, therefore the product is stored in dry condition.

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Pasteurization is a process for preservation of liquid food. This method was invented by Louis Pasteur in 1862. Milk is heated up to 70ºc to kill the bacteria and it is cooled to 10ºc to prevent the growth of remaining bacteria. Then milk is stored in sterilized bottles in cold places.

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Scientists discovered a particular strain of probiotic Bifidobacterium bifidum can help to repair stomach ulcers caused by Helicobacter pylori. Another probiotic in this genus, Bifidobacterium breve, is useful in the treatment of childhood constipation.

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Thousands of bacteria, fungi and other microbes that live in our gut are essential contributors to a good health. They break down toxins, manufacture some vitamins and essential amino acids and form a barrier against invaders

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Gut microbes are the bacteria in human gut. It is one of the most important allies in our overall health and well-being. Gut ensures that the body is absorbing all the important nutrients, to function at its highest level. Many different aspects of health are attached to it.

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The word prion is derived from “protinaceous infectious particle”. Prions have neither DNA or RNA to transmit infection. A prion is a mutted form of a usually harmless protein. Prions cause diseases by affecting brain or neural tissue

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Virion is an entire virus particle consisting of an outer protein shell called a capsid and an inner core of nucleic acid (RNA or DNA). If the virus is found outside the cell (extracellular) it is known as virion. Virion has the capacity to infect the living tissue.