Microorganisms : Friend And Foe

Viruses reproduce inside the cells of organisms like plants, animals or bacteria. Outside the body of the host they show no signs of life but when it enters a host cell it reproduces or replicates.

Influenza which is also known as flu is an infectious disease caused by influenza virus and it symptoms includes high fever, running nose, sore throat, headache, coughing etc.

Antibiotics are the medicines which inhibit the growth of microbes. Antibiotics are mainly produced from certain bacteria and fungi. These antibiotics can be used to control microbial diseases in plants and animals.

Lichen is a symbiotic association of algae and fungi where algae provide food and fungi provides shelter.

During preparation of bread yeast converts sugar to alcohol and release carbon dioxide gas by the process of fermentation.

Malaria is caused due to the bite of female Anopheles mosquitoes which carry protozoan Plasmodium in their saliva.

Waste in pit B as waste is left open i.e. without being wrapped in a polythene bag so microbes could easily degrade them as wastes come in direct contact with oxygen gas. But in pit A as wastes are wrapped in polythene bag oxygen could not enter hence the process of degradation will be slow.

(a) Antibodies

Our body produces substances called antibodies when a disease-causing microbes enter into our body which fights and destroy the pathogens and remain in the body to fight future infections caused by the same pathogen.

(b) Tuberculosis

Tuberculosis is caused by bacterium Mycobacterium tuberculosis which is an air-borne disease. It generally attacks the lungs. BCG vaccine is given to prevent tuberculosis.

(c) Anthrax

Anthrax is a bacterial disease caused by Bacillus anthracis and is usually transmitted from cattles.

(d) Fermentation

Fermentation is the process by which yeasts convert sugar into alcohol and produce carbon dioxide gas in absence of oxygen gas.

(a) Preservatives

Preservatives are the chemicals that control microbial growth and helps in prevents of spoilage of food. Examples – Sodium benzoate, potassium metabisulphite etc.

(b) Rhizobium

Rhizobium is a nitrogen-fixing bacteria present in nodules of roots of leguminous plants which converts atmosphere nitrogen to nitrites or nitrates that is required for plants.

(c) Carrier/Vector

Vector carry pathogens for example – female Anopheles mosquito carries Plasmodium which causes malaria.

(d) Antibiotics

Antibiotics are the chemicals which destroy or inhibit the growth of disease-causing microbes and are produced by certain bacteria or fungi.

a) – iii

b) – ii

c) – v

d) – i

The process of conversion of sugar into an acid or an alcohol by the action of microbes is called fermentation and it was first discovered by Louis Pasteur.

Robert Koch discovered the bacterium which causes anthrax.

Edward Jenner discovered a vaccine for small pox.

Alexander Fleming discovered penicillin antibiotic from the fungus Penicillium notatum.

One commercial use of yeast is making bread.

Bread dough is a mixture of flour, water, salt, sugar, yeast cells. Yeast converts sugar to alcohol and carbon dioxide. Due to the production of carbon dioxide gas, the dough rises in volume and bread becomes porous and spongy.

Fermentation is the process that converts sugar into alcohol.

This process is helpful for making bread and alcoholic beverages.

In the soil, nitrogen gets enriched by cyanobacteria or blue-green algae.

They convert atmospheric nitrogen to nitrites or nitrates. They are called nitrogen-fixing bacteria.

We should avoid standing close to a tuberculosis patient while he/she is coughing as tuberculosis is an air-borne disease and it gets easily spreads through the air.

When an infected person cough, the pathogen spreads and remain suspended as droplets in the air and can easily infect a healthy person.

Polio drops are not given to children suffering from diarrhea as it is an oral vaccine and due to frequent motions it may get excreted from the body. As a result, the vaccine may get ineffective in fighting against the polio virus.

Oil was poured on the top of the pickle as it acts as a preservative and prevents microbial growth thus protects the pickle from getting spoiled.

a – iv

b – iii

c – i

d – ii

Lactobacillus is a bacteria which converts the lactose sugar present in milk to lactic acid. Thus it helps in converting milk into curd.

Aspergillus is fungi which cause black mold disease on certain fruits and vegetables.

Spirogyra is an algae and is an important source of protein and are used as food supplements.

Paramecium is protozoa and is a minute, unicellular microorganisms found in water bodies.

Friendly microbes are yeasts, Lactobacillus, Rhizobium.

Yeasts are used commercially for making bread and alcoholic beverages. Rhizobium is a nitrogen-fixing bacteria present in nodules of leguminous plants which convert atmospheric nitrogen into nitrites and nitrates. Lactobacillus converts milk to curd.

Harmful microbes are malaria parasite, Bacillus anthracis, bread mold.

Malaria parasite present in the saliva of female Anopheles mosquitoes when it bites causes malaria. Bacillus anthracis is the causative pathogen of anthrax. Bread mold spoils the bread and when these spoiled bread is consumed it can cause food poisoning.

The reason could be the chaat might have been contaminated with pathogens due to unhygienic conditions near the chaat shop or utensils in which chaat was served.

If the food is left uncovered the flies might sit on the food and spreads disease-causing pathogens, so when Boojho ate that contaminated food he felt ill and complains of a stomach ache.

If pooris and unused kneaded flour are left in the open for a day or two they get contaminated by microbes which cause fermentation of the dough and it would result spoilage of kneaded flour.

But the pooris as they are fried they will remain good as they are deeply fried which killed the microbes.

a) The two diseases caused by the virus are common cold, poliomyelitis

The common cold is caused by a virus and easily gets spread through the air, direct contact with infected person etc. Poliomyelitis is caused by polio virus and Salk’s vaccine is given to prevent this disease.

b) One important characteristic of a virus is that it can reproduce only inside a host cell.

The host cell may be a plant or animal or bacteria.

a) The name of the disease is Yellow vein mosaic of lady’s finger which is characterized by alternating yellow and green patches and chlorosis in veins of the leaves.

b) The causative agent of this disease is a virus.

c) The disease is spread by insects from one plant to the other plant.

d) The two plant diseases are

i. Apple scab caused by a fungus

ii. Citrus canker caused by a bacteria.

A vaccine is a preparation of killed or weakened disease-causing microbes and when it is introduced into the body of a healthy person, the body produces antibodies against these microbes. These antibodies remain in the body and protect us from infections in the future caused by the same microbes.

a) The sugar solution present in flask A due to the action of yeast gets converted into ethanol and carbon dioxide. This process is called fermentation.

b) Carbon dioxide gas is released in flask A.

c) The lime water present in test tube B turns milky due to the production of carbon dioxide gas in flask A which passes through the delivery tube into lime water present in a test tube and makes it milky.

a) Cholera can be prevented by maintaining proper sanitation practices and proper hygiene, boiling water before drinking, avoid eating uncovered food and food from vendors.

b) Typhoid can be prevented by maintaining proper personal hygiene and sanitation practices, eating properly cooked food, drinking boiled water, getting vaccinated from this disease.

c) Hepatitis A can be prevented by taking the vaccine, drinking boiled water, properly cooked food etc.

a) Lightning fixes atmospheric nitrogen.

b) Nitrogen-fixing bacteria and blue-green algae fix atmospheric nitrogen.

c) Nitrogenous waste from excretion by animals and plants and decomposition of dead plants and animals.

d) Nitrogen released by bacteria from nitrogenous compounds present in soil into air.