Serial dilution technique-

Listar and his coworkers employed this technique to separate a single species from a mixture in which it was a predominating type. A small amount of the material, which contains mixture of bacteria is added to a test tube containing sterile medium of known volume. A stage will be reached when higher dilutions will contain no organisms and will show no growth upon incubation. Some of the tubes of higher dilution showing will be found to contain only one colony of a species, which can be ascertained by microscopic examination.





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Streak plate technique-

The inoculum is streaked or spread over the surface of a solid medium. The streaking process accomplishes a thinking out of the population. There is no uniform distribution of the organism. Where they are thickly populated, they will grow in mass, but where only few are present, they develop distinct colonies. These isoalated colonies are the progenies of single cells and whether they are so may be verified from microscopic examination. Pure culture may be recurred by the transfer of a part of such colonies to a container with suitable culture medium.

Single-cell isolation technique-

The best way to secure a pure culture from a mixed one would like to pick out a single cell of the desired type. This can be done by the use of micromanipulator in contamination with a microscope. Micromanipulator has a micropipette with a very fine capillary point. The micropipette can be moved as desire. A single cell can be picked using micropipette and transferred to a suitable nutrient medium.

Disadvantages-
This technique requires a skilled operator, is cumbersome to operate and involves greater chances of contamination during operation.

Direct transfer technique-

Sometimes beacteria, yeasts and moulda may be found in pure culture under conditions. Such cultures can be directly transferred to a suitable medium. Several molds produce aerial conidia which are comparatively free from comtaminations.
A pure culture can be obtained by transfer of infected blood with proper precautions to avoid contamination.

Numerical taxonomy-

Isolation of pure culture-
Growth of microbes in or on a laboratory medium is known as “Culture”. A growth of this type on a solid medium, which has originated from a single cell or spore is termed “colony”. A culrure, which contains only one species of microbe is termed a “ pure culture” and one which consists of several species is called a “mixed culture”.
Microbes are ubiquitous. It is very difficuly to obtain pure cultures of bacteria in nature.they usually exist as mixed cultures in their natural habitats, but it is essential to have pure culture of an organism before one can study its charasteristics. To obtain organisms in pure cultures various techniques have been employed.

Genetic or Molecular approach-

Phenotypic characteristics of any given organisms are the expression of a large number of genes that control the expression of genes is ultimately determined by DNA baksequence of bacteria.

Classical approach-

The classification is based on numerous properties: morphological, cultural, nutritive, biochemical, physiological, serologic, bacteriophage succeptibility pathogenic and genetic properties of organism.
Adansonian approach-
It resembles the classical approach in that a large number of charecteristics are determined for each organism of a group, but each phenotypic characteristics is given equal merit rather than placing more weight on some characteristics than on others.

Main approches to microbial classification-

1) Classical approach
2) Adansonian approach
3) Genetic or Molecular
4) Numerical taxonomy

Fundamental principles of Microbiology

Microbiology is a branch of biological science and includes the study of microscopic living beings both plant and animal such as bacteria. Bacteria belongs to a group of living organisms known as microbes without distinction regarding whether they are plants or animal. They are so called because of their small size. The study of micro organisms is a basic prerequisite because bacteria resume as living models.
The very best human eyes, unaided, failed to see objects less than about 100mm. So there was a need to make use of magnifying lens and see the microscopic objects. Robert Hooks made and used a compound microscope and observed moulds.

Transmission-

Human beings themselves are the main reserviour of most diseases that affect them. Transmission of the excreata-related diseases from one host to another follows one of the routes.
Control-
If transmission of diseases blocked at one or more points, excreate-related diseases can be controlled or possibly eradicated. Good sanitation practice can help towards the goal. eg. Water-seal slabs in latrine reduce the breeding sites for mosquotoes, vectors of filariasis. Treatement of excerata prior to its disposal can kill the eggs and cysts of many human parasites like Ascasis, Entamoeba, Schistosoma spp thus preventing contamination of both ground and water. Instead of treating human excreata as a social problem, if ways are devised where it could be used as a natural resources to be conserved and reused under careful control, then many of the associated problems could be corrected. There are three basic methods of using this sources.

Solid waste disposal and control-

The inadequate and insanitary disposal of infected human faeces leads to the contamination of the ground and of sources of water. It provides the sites and the opportunity for certain species of files and mosquitoes to lay their eggs, to breed, or to feed on the exposed material and to carry infection. It also attracts domestic animals, rodents which apread the faeces and also the potential for the diseases. In addition, it intolerable nuisance of odour and sight. There are number of communibale and noncommunibale diseases related to excreta and waste water. Major communicable diseases are intenstinal infections and helminth infestations, cholera, typhoid, paratyphoid, dysentery and diarrhea, hookworm, schistosomiasis and filariasis. Some of pathogenic organisms found in faeces, urine etc.

Prevention-

Many of the sources of noise can be controlled by public. Blowing of automobile horns, rattling trucks, noisy breaks, loud speaker, loud radios are some such examples. Prevention of noise will require
1) Education of the public
2) Co-operation of the industrial entrepreneurs, transport authorities and
3) Enforcement of adequate legislative measures.
The community may have demarcation of silent zones in different areas of a city, prohibition of blowing of horns near hospitals, schools and public offices, use of horns that are free from shrill etc. Use of loud speakers and loud radios can be restricted.

Noise-

A sound becomes noise when it causes disturbance to the hearer. Noise is measured in units of decibel. Loud noise may be cause direct injury to the auditory organs resulting in deafness. Permanent deafiness may be caused by exposure to sudden noise of an explosive nature. Temporary deafiness may occure after exposure to a light intense sound from jet engine. It has been observed that normal development of infants is interfered with by constant loud noise. Noise interfered with restful sleep. Onset of cardiovascular and cerebrovascular syndromes has been associated with disturnbance by noise.

Air borne harmful agents-

These agents are dust, industrial waste and industrial pollutants. Cities with heavy industries and vehicular transport can lead to pneumoconiosis, silicosis, lead poisoning etc.
Light-
Natural or artificial light is available at all places. Natural sunlight should be used wherever possible both for economy and for its beneficial effect on health. It is obtained by providing windows which should have an area of at least 1/10th of floor space. The rays of sun include visible rays, heat rays and invisible ultraviolet rays.in industries, inadequate lighting is uneconomical as the output leads to fall and the accident rate might increase. No worker should be permitted to gage directly at a bright light and every effort should be made to ensure that glazing light does not enter the eye obliquely.

Bacteria

Pathogenic microbes are present only in the vicinity of patients with related diseases.
Ventilation considers maintaining atmospheric conditions which are comfortable for the human body. The amount of air required for sufficient ventilation depends on factors like size of the room, number of persons on factors like size of room, no of persons occupying the room & impurities present in the room. In order to limit the concentration of carbon dioxide to less than 0.02%, each individual is advised to have at least 3000 c.ft.air per hour. In case of sick persons it is advised to be increased to 3750 c. ft. If the space available per head is a fraction of the required minimum then the air will have to be changed frequently e.g.300 c.ft.requires air to be changed at the rate of 10 times per hour. It is observed that warm air, after rising to the height of 12 feet, gets cooled & falls down again. Thus for a floor height of about 12 feet, the floor space should be 1/12 th of the total cubic space.

Dust

The inorganic particles in atmosphere are composed of silica, aluminium silicate, carbonate and phosphate of calcium, magnesium etc. Particles in the air of houses contain debris arising from wear and tear of articles like soot, ashes, scales of fibres of cotton, particles of hair, spores, pollen grains etc.

Respiration of air-

The major impurities in the expired air are carbon di-oxide, water vapours and organic matter . when the amount of air of a particular room rises to above person, the air becomes stuffy, however stagnation of air and reduced oxygen are the contributory factors to cause symtoms like drowsiness, headache, nausea etc. in over-crowded rooms. In case of persons suffering from pneumonia, diphtheria, tuberculosis etc. microbes in large numbers may come out during coughing, sneezing loud-speaking.

Health and air, noise, light-

Air-
The two mportant functions of air are-1) interchange of gases in the process of respiration 2) regulation of body temperature.
pure air has following composition-
1) Oxygen 20.95%
2) Carbon dioxide 0.03 to 0.4%
3) Nitrogen 79%
4) Water vapour variable
5) Ammonia,Ozone, Argon, Mineral Salt: traces
In open air the composition is fairly constant because of air currents, activities of plants etc. water content in the air are variable. During rainfall or in the vicinityu of the sea, huminity is higher. About 65% to 75% of humidity is considered conducive for health. The wind, the rain, oxygen and photosynthetic activities because of green content in the leaves are the important factors on which purification of air depends.