Microbes in Human Welfare1.Microbes in Household Products
Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd.
During growth, the LAB produce acids that coagulate and partially digest the milk proteins.
A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin \[{{B}_{12}}\].
In our stomach too, the LAB play very beneficial role in checking diseasecausing microbes.
The dough, which is used for making foods such as dosa and idii is also fermented by bacteria. The puffed-up appearance of dough is due to the production of \[C{{O}_{2}}\], gas.
Similarly the dough, which is used for making bread, is fermented using baker's yeast (Saccharomyces cerevisiae).
A number of traditional drinks and foods are also made by fermentation by the microbes. 'Toddy', a traditional drink of some parts of southern India is made by fermenting sap from palms.
Microbes are also used to ferment fish, soyabean and bambooshoots to make foods. Cheese, is one of the oldest food items in which microbes were used.
Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbes used.
The 'Roquefort cheese' are ripened by growing a specific fungi on them, which gives them a particular flavour.
2.Microbes in Industrial Products
Even in industry, microbes are used to synthesise a number of products valuable to human beings. Beverages and antibiotics are some examples. Production on an industrial scale, requires growing microbes in very large vessels called fermentors.
Microbes especially yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky, brandy or rum.
For this purpose the same yeast Saccharomyces cerevisiae used for bread-making and commonly called brewer's yeast, is used for fermenting mailed cereals and fruit juices, to produce ethanol.
Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes.
Penicillin was the first antibiotic to be discovered, and it was a chance discovery. Alexander Fleming while working on Staphylococci bacteria, once observed a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. He more...
Muscle Skeletal and Neural System1.Muscle and Skeletal
Muscle is a specialised tissue of mesodermal origin. About \[40-50\]per cent of the body weight of a human adult is contributed by muscles. They have special properties like excitability, contractility, extensibility and elasticity.
Muscles have been classified using different criteria, namely location, appearance and nature of regulation of their activities.
Based on their location, three types of muscles are identified-Skeletal, Visceral and Cardiac.
Skeletal muscles are closely associated with the skeletal components of the body. They have a striped appearance under the microscope and hence are called striated muscles. As their activities are under the voluntary control of the nervous system, they are known as voluntary muscles too. They are primarily involved in locomotory actions and changes of body postures.
Visceral muscles are located in the inner walls of hollow visceral organs of the body like the alimentary canal, reproductive tract, etc. They do not exhibit any striation and are smooth in appearance. Hence, they are called smooth muscles (nonstriated muscle). Their activities are not under the voluntary control of the nervous system and are therefore known as Avoluntary muscles. They assist, for example, in the transportation of food through the digestive tract and gametes through the genital tract.
Cardiac muscles are the muscles of heart. Many cardiac muscle cells assemble in a branching pattern to form a cardiac muscle. Based on appearance, cardiac muscles are striated. They are involuntary in nature as the nervous system does not control their activities directly.
Skeletal system consists of a framework of bones and a few cartilages. This system has a significant role in movement shown by the body. Imagine chewing food without jaw bones and walking around without the limb bones. Bone and cartilage are specialized connective tissues.
The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts.
In human beings, this system is made up of 206 bones and a few cartilages. It is grouped into two principal divisions - the axial and the appendicular skeleton.
Axial skeleton comprises 80 bones distributed along the main axis of the body. The skull, vertebral column, sternum and ribs constitute axial skeleton. The skull is composed of two sets of bones - cranial and facial, that totals to 22 bones.
Cranial bones are 8 in number. They form the hard protective outer covering, cranium for the brain. The facial region is made up of 14 skeletal elements which form the front part of the skull.
A single U-shaped bone called hyoid is present at more...
In Linnaeus' time a Two Kingdom system of classification with Plantae and Animalia kingdoms was developed that included all plants and animals respectively.
H. Whittaker (1969) proposed a Five Kingdom Classification. The kingdoms defined by him were named Monera, Protista, Fungi, Plantae and Animalia. Earlier classification systems included bacteria, blue green algae, fungi, mosses, ferns, gymnosperms and the angiosperms under 'Plants'. The character that unified this whole kingdom was that all the organisms included had a cell wall in their cells. This placed together groups which widely differed in other characteristics.
It brought together the prokaryotic bacteria and the blue green algae with other groups which were eukaryotic. It also grouped together the unicellular organisms and the multicellular ones, say, for example, Chlamydomonas and Spirogyra were placed together under algae.
The classification did not differentiate between the heterotrophic group - fungi, and the autotrophic green plants, though they also showed a characteristic difference in their walls composition - the fungi had chitin in their walls while the green plants had a cellulosic cell wall.
When such characteristics were considered, the fungi were placed in a separate kingdom - Kingdom Fungi. All prokaryotic organisms were grouped together under Kingdom Monera and the unicellular eukaryotic organisms were placed in Kingdom Protista.
Kingdom Protista has brought together Chlamydomonas, Chlorella (earlier placed in Algae within Plants and both having cell walls) with Paramoecium and Amoeba (which were earlier placed in the animal kingdom which lack cell wall). It has put together organisms which, in earlier classifications, were placed in different kingdoms. This happened because the criteria for classification changed.
2.Kingdom Monera
Bacteria are the sole members of the Kingdom Monera. They are the most abundant micro-organisms.
Though the bacterial structure is very simple, they are very complex in behaviour. Compared to many other organisms, bacteria as a group show the most extensive metabolic diversity. Some of the bacteria are autotrophic, i.e., they synthesise their own food from inorganic substrates. They may be photosynthetic autotrophic or chemosynthetic autotrophic. The vast majority of bacteria are heterotrophs, i.e., they do not synthesise their own food but depend on other organisms or on dead organic matter for food.
Archaebacteria are special since they live in some of the most harsh habitats such as extreme salty areas (halophiles), hot springs (thermoacidophiles) and marshy areas (methanogens).
Archaebacteria differ from other bacteria in more...
The flowers perform the function of reproduction in plants. Flowers are the reproductive parts of a plant. A flower may have either the male part or the female part or both male and female parts.
There are several ways by which plants produce their offspring. These are categorized into two types-asexual and sexual reproduction. In asexual reproduction plants can give rise to new plants without seeds, whereas in sexual reproduction, new plants are obtained from seeds.
In asexual reproduction new plants are obtained without production of seeds or spores.
Vegetative propagation is a type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds. Since reproduction is through the vegetative parts of the plant, it is known as vegetative propagation.
Yeast is a single-celled organism.
Flowers are the reproductive parts of a plant. The stamens are the male reproductive part and the pistil is the female reproductive part.
The flowers which contain either only the pistil or only the stamens are called unisexual flowers. The flowers which contain both stamens and pistil are called bisexual flowers.
Corn, papaya and cucumber produce unisexual flowers, whereas mustard, rose and petunia have bisexual flowers.
Both the male and the female unisexual flowers may be present in the same plant or in different plants.
Anther contains pollen grains which produce male gametes. A pistil consists of stigma, style and ovary. The ovary contains one or more ovules. The female gamete or the egg is formed in an ovule.
In sexual reproduction a male and a female gamete fuse to form a zygote.
Generally pollen grains have a tough protective coat which prevents them from drying up. Since pollen grains are light, they can be carried by wind or water. Insects visit flowers and carry away pollen on their bodies. Some of the pollen lands on the stigma of a flower of the same kind.
The transfer of pollen from the anther to the stigma of a flower is called pollination. If the pollen lands on the stigma of the same flower it is called self-pollination. When the pollen of a flower lands on the stigma of another flower of the same plant, or that of a different plant of the same kind, it is called cross-pollination.
The cell which results after fusion of the gametes is called a zygote. The process of fusion of male and female gametes (to form a zygote) is called fertilisation. The zygote develops into an embryo.
After fertilisation, the ovary grows into a fruit more...
If we pull out any weed we will see that all of them have roots, stems and leaves. They may be bearing flowers and fruits. The underground part of the flowering plant is the root system while the portion above the ground forms the shoot system.
In majority of the dicotyledonous plants, the direct elongation of the radicle leads to the formation of primary root which grows inside the soil. It bears lateral roots of several orders that are referred to as secondary, tertiary, etc. roots. The primary roots and its branches constitute the tap root system, as seen in the mustard plant.
In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots. These roots originate from the base of the stem and constitute the fibrous root system, as seen in the wheat plant.
In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious roots.
The main functions of the root system are absorption of water and minerals from the soil, providing a proper anchorage to the plant parts, storing reserve food material and synthesis of plant growth regulators.
From this region some of the epidermal cells form very fine and delicate, thread-like structures called root hairs. These root hairs absorb water and minerals from the soil.
Roots in some plants change their shape and structure and become modified to perform functions other than absorption and conduction of water and minerals. They are modified for support, storage of food and respiration. Tap roots of carrot, turnip and adventitious roots of sweet potato, get swollen and store food.
Hanging structures that support a banyan tree, these are called prop roots.
Similarly, the stems of maize and sugarcane have supporting roots coming out of the lower nodes of the stem. These are called stilt roots.
In some plants such as Rhizophora growing in swampy areas, many roots come out of the ground and grow vertically upwards. Such roots, called pneumatophores, help to get oxygen for respiration.
2.The Stem
The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits. It develops from the plumule of the embryo of a germinating seed.
The main function of the stem is spreading out branches bearing leaves, flowers more...
The composition of air is the result of life on Earth. In planets such as Venus and Mars, where no life is known to exist, the major component of the atmosphere is found to be carbon dioxide.
In fact, carbon dioxide constitutes up to \[95-97\]per cent of the atmosphere on Venus and Mars. Eukaryotic cells and many prokaryotic cells need oxygen to break down glucose molecules and get energy for their activities.
Despite this, the percentage of carbon dioxide in our atmosphere is a mere fraction of a percent because carbon dioxide is 'fixed’ in two ways : Green plants convert carbon dioxide into glucose in the presence of Sunlight and many marine animals use carbonates dissolved in sea-water to make their shells.
We have talked of the atmosphere covering the Earth, like a blanket. We know that air is a bad conductor of heat. The atmosphere eeps the average temperature of the Earth fairly steady during the day and even during the course of the whole year. The atmosphere prevents the sudden increase in temperature during the daylight hours. And during the night, it slows down the escape of heat into outer space. Think of the moon, which is about the same distance from the Sun that the Earth is. Despite that, on the surface of the moon, with no atmosphere, the temperature ranges from -\[190{}^\circ \]C to \[110{}^\circ \]C.
But why is water so necessary? And do all organisms require water? All cellular processes take place in a water medium. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water. Substances are also transported from one part of the body to the other in a dissolved form.
Hence, organisms need to maintain the level of water within their bodies in order to stay alive. Terrestrial life-forms require fresh water for this because their bodies cannot tolerate or get rid of the high amounts of dissolved salts in saline water. Thus, water sources need to be easily accessible for animals and plants to survive on land.
So, we use the term water-pollution to cover the following effects :
The addition of undesirable substances to water-bodies. These substances could be the fertilisers and pesticides used in farming or they could be poisonous substances, like mercury salts which are used by paper-industries. These could also be disease- causing organisms, like the bacteria which cause cholera.
The removal of desirable substances from water-bodies. Dissolved oxygen is used by the animals and plants that live in water. Any change that reduces the amount of this more...
Biotechnology: Principles and Processes1.Principles of Biotechnology
Biotechnology deals with techniques of using live organisms or enzymes from organisms to produce products and processes useful to humans.
In this sense, making curd, bread or wine, which are all microbe-mediated processes, could also be thought as a form of biotechnology.
However, it is used in a restricted sense today, to refer to such of those processes which use genetically modified organisms to achieve the same on a larger scale.
Further, many other processes/techniques are also included under biotechnology. For example, in vitro fertilization leading to a 'test-tube9 baby, synthesising a gene and using it, developing a DNA vaccine or correcting a defective gene, are all part of biotechnology.
The European Federation of Biotechnology (EFB) has given a definition of biotechnology that encompasses both traditional view and modem molecular biotechnology.
We probably appreciate the advantages of sexual reproduction over asexual reproduction. The former provides opportunities for variations and formulation of unique combinations of genetic setup, some of which may be beneficial to the organism as well as the population. Asexual reproduction preserves the genetic information, while sexual reproduction permits variation.
Traditional hybridisation procedures used in plant and animal breeding, very often lead to inclusion and multiplication of undesirable genes along with the desired genes.
The techniques of genetic engineering which include creation of recombinant DNA, use of gene cloning and gene transfer, overcome this limitation and allows us to isolate and introduce only one or a set of desirable genes without introducing undesirable genes into the target organism.
The construction of the first recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid (autonomously replicating circular extra-chromosomal DNA) of Salmonella typhimurium. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance.
The cutting of DNA at specific locations became possible with the discovery of the so-called 'molecular scissors9- restriction enzymes. The cut piece of DNA was then linked with the plasmid DNA. These plasmid DNA act as vectors to transfer the piece of DNA attached to it.
We probably know that mosquito acts as an insect vector to transfer the malarial parasite into human body. In the same way, a plasmid can be used as vector to deliver an alien piece of DNA into the host organism.
The linking of antibiotic resistance gene with the plasmid vector became possible with the enzyme DNA ligase, which acts on cut DNA molecules more...
The atmosphere that surrounds the earth is not of the same thickness at all heights. There are concentric layers of air or regions and each layer has different density.
The lowest region of atmosphere in which the human beings along with other organisms live in called troposphere. It extends up to the height of \[\sim 10\] km from sea level. Above the troposphere, between \[10\] and \[50\] km above sea level lies stratosphere.
Troposphere is a turbulent, dusty zone containing air, much water vapour and clouds. This is the region of strong air movement and cloud formation. The stratosphere, on the other hand, contains dinitrogen, dioxygen, ozone and little water vapour.
Atmospheric pollution is generally studied as tropospheric and stratospheric pollution. The presence of ozone in the stratosphere prevents about \[99.5\]per cent of the sun's harmful ultraviolet (UV) radiations from reaching the earth's surface and thereby protecting humans and other animals from its effect.
Pollution occurs due to the presence of undersirable solid or gaseous particles in the air. Gaseous air pollutants are oxides of sulphur, nitrogen and carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants. Particulate pollutants are dust, mist, fumes, smoke, smog etc.
Oxides of Sulphur
Oxides of sulphur are produced when sulphur containing fossil fuel is burnt. The most common species, sulphur dioxide, is a gas that is poisonous to both animals and plants.
It has been reported that even a low concentration of sulphur dioxide causes respiratory disease e.g., asthma, bronchitis, emphysema in human beings.
Sulphur dioxide causes irritation to the eyes, resulting in tears and redness.
High concentration of \[S{{O}_{2}}\] leads to stiffness of flower buds which eventually fall of from plants. Uncatalysed oxidation of sulphur dioxide is slow. However, the presence of particulate matter in polluted air catalyses the oxidation of sulphur dioxide to sulphur trioxide.
The reaction can also be promoted by ozone and hydrogen peroxide.
Oxides of Nitrogen
Dinitrogen and dioxygen are the main constituents of air. These gases do not react with each other at a normal temperature. At high altitudes when lightning strikes, they combine to from oxides of nitrogen.
\[N{{O}_{2}}\] is oxidised to nitrate ion, \[N{{O}^{-}}_{3}\] which is washed into soil, where it serves as a fertilizer. In an automobile engine, (at high temperature) when fossil fuel is burnt, dinitrogen and dioxygen combine to yield significant quantities of nitric oxide \[\left( NO \right)\]and nitrogen dioxide \[\left( N{{O}_{2}} \right)\].
Rate of production of \[N{{O}_{2}}\] is faster when nitric oxide reacts with ozone in the stratosphere. The irritant red haze in the traffic and congested more...
Carbohydrates are primarily produced by plants and form a very large group of naturally occurring organic compounds. Some common examples are cane sugar, glucose, starch, etc.
Some of the carbohydrates, which are sweet in taste, are also called sugars. The most common sugar, used in our homes is named as sucrose whereas the sugar present in milk is known as lactose.
Carbohydrates are classified on the basis of their behaviour on hydrolysis. They have been broadly divided into following three groups.
Monosaccharides: A' carbohydrate that cannot be hydrolysed further to give simpler unit of polyhydroxy aldehyde or ketone is called a monosaccharide. About 20 monosaccharides are known to occur in nature. Some common examples are glucose, fructose, ribose, etc.
Oligosaccharides: Carbohydrates that yield two to ten monosaccharide units, on hydrolysis, are called oligosaccharides. They are farther classified as disaccharides, trisaccharides, tetrasaccharides, etc., depending upon the number of monosaccharides, they provide on hydrolysis. Amongst these the most common are disaccharides. The two monosaccharide units obtained on hydrolysis of a disaccharide may be same or different. For example, sucrose on hydrolysis gives one molecule each of glucose and fructose whereas maltose gives two molecules of glucose only.
Polysaccharides: Carbohydrates which yield a large number of monosaccharide units on hydrolysis are called polysaccharides. Some common examples are starch, cellulose, glycogen, gums, etc. Polysaccharides are not sweet in taste, hence they are also called non-sugars.
Glucose occurs freely in nature as well as in the combined form. It is present in sweet fruits and honey. Ripe grapes also contain glucose in large amounts.
Glucose is an aldohexose and is also known as dextrose. It is the monomer of many of the larger carbohydrates, namely starch, cellulose. It is probably the most abundant organic compound on earth.
Fructose is an important ketohexose. It is obtained along with glucose by the hydrolysis of disaccharide, sucrose. Another disaccharide is maltose.
Lactose is more commonly known as milk sugar since this disaccharide is found in milk.
Starch is the main storage polysaccharide of plants. It is the most important dietary source for human beings. High content of starch is found in cereals, roots, tubers and some vegetables. It is a polymer of \[\alpha \]-glucose and consists of two components – Amylose and Amylopectin.
Cellulose occurs exclusively in plants and it is the most abundant organic substance in plant kingdom. It is a predominant constituent of cell wall of plant cells.
The carbohydrates are stored in animal body as glycogen. It is also known as animal starch because its structure is similar to amylopectin and is rather more...
Antibiotics are used as drugs to treat infections because of their low toxicity for humans and animals. Initially antibiotics were classified as chemical substances produced by microorganisms (bacteria, fungi and molds) that inhibit the growth or even destroy microorganisms.
The development of synthetic methods has helped in synthesising some of the compounds that were originally discovered as products of microorganisms. Also, some purely synthetic compunds have antibacterial activity, and therefore, definition of antibiotic has been modified. An antibiotic now refers to a substance produced wholly or partly by chemical synthesis, which in low concentration inhibits the growth or destroys microorganisms by intervening in their metabolic processes.
The search for chemicals that would adversely affect invading bacteria but not the host began in the nineteenth century. Paul Ehrlich, a German bacteriologist, conceived this idea. He investigated arsenic based structures in order to produce less toxic substances for the treatment of syphilis. He developed the medicine, arsphenamine, known as salvarsan.
Paul Ehrlich got Nobel prize for Medicine in 1908 for this discovery. It was the first effective treatment for syphilis. Although salvarsan is toxic to human beings, its effect on the bacteria, spirochete, which causes syphilis is much greater than on human beings.
The range of bacteria or other microorganisms that are affected by a certain antibiotic is expressed as its spectrum of action. Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are said to be broad spectrum antibiotics. Those effective mainly against Gram-positive or Gram-negative bacteria are narrow spectrum antibiotics.
If effective against a single organism or disease, they are referred to as limited spectrum antibiotics. Penicillin G has a narrow spectrum. Ampicillin and Amoxycillin are synthetic modifications of penicillins. These have broad spectrum. It is absolutely essential to test the patients for sensitivity (allergy) to penicillin before it is administered.
2.Antiseptics and disinfectants
Antiseptics and disinfectants are also the chemicals which either kill or prevent the growth of microorganisms.
Antiseptics are applied to the living tissues such as wounds, cuts, ulcers and diseased skin surfaces. These are not ingested like antibiotics.
Commonly used antiseptic, dettol is a mixture of chloroxylenol and terpineol Bithionol (the compound is also called bithional) is added to soaps to impart antiseptic properties.
Iodine is a powerful antiseptic. Its \[2-3\]per cent solution in alcohol water mixture is known as more...
