Differences between active immunity and passive immunity system
Features | Active Immunity | Passive Immunity |
Definition | The construction of antibodies against a definite agent by the immune system. | This immunity is produced by the transfer to one person of antibodies that were produced by another person. Protection from passive immunity diminishes in a moderately short time, normally a few weeks or months. |
Develop | Slowly & normally | quickly. |
Protection duration | Long lasting,often gives protection for many years. | Protecton is lost within two or three weeks. |
Application | Main application is prophylaxis. | Application is in both porphylactically & therapeutically. |
Natural Production | Acquired by clinical or sub clinical infection. | Naturally fetus get immunity from the mother. |
Artificial source | Artificially it is achieved by administration of antigenic preparation. | Artificially it is achieved by injection of antibodies produced in animals. |
Preparation | Known as vaccine | Known as anti-sera,sera or immune sera. |
What are the reasons of underlying unusual resistance shown by endospores?
Ans:
Endospores are capable of surviving at levels of dehydration. The low water content also provides the endospore with chemical resistance (to chemicals such as hydrogen peroxide) and it causes the remaining enzymes of the spore cell to become inactive.
Dipicolinic acid is the another chemical to lend endospore to high resistance.It reacts with calcium dipicolinate, which is the main substance believed to lend endospores to their resistance and represents about 10% of the dry weight of an endospore. The spore cell also contains small acid-soluble spore proteins (SASPs). These function is to protect DNA from UV radiation, dessication and dry heat.
Sporulation is a complex process including as many as 200 genes. These genes are stimulated by an environmental trigger, causing sporulation of the cell. The steps leading to endospore formation result in the creation of a dry, metabolically inert and extremely resistant endospore from a moist.
The Methods of Measurements of Microbial Growths.
* Direct measurement of microbial growth
1.Plate counts-most used method/require serial dilutions. example-pour plates (30-300 colonies countable)
2.Filtration-passage of liquid through a grid containing small pores (< .45 um)
3.Most Probable Number-statistical method used with bacteria that won’t grow on media
4.Direct Microscopic Count-known volume of bacterial suspension placed on special cell counting slide
* Indirect Methods of Estimating Bacterial Numbers
1.Turbidity-cloudiness produced as media becomes filled with bacteria
2.Metabolic Activity-assumes certain amounts of metabolic wastes are in direct proportion to amount of bacteria
3.Dry Weight-organisms removed from media, filtered, and weighed
