CONTROL OF MICROORGANISMS BY PHYSICAL METHOD..

2) RADIATION:  
       Radiation is the energy transmitted through the space in the varieties of forms. Major types of radiations includes ionizing radiation; UV radiation, Ultrasonication.

i) Ionizing Radiation: It has high energy & can ionize the atoms. They have energy above 10eV. On such radiation pass via cells they create unstable ions & free radicals(H- radicals, OH-radicals, & some peroxides). This radical causes different types intracellular damage whereas ions combines & destroys proteins & nucleic acids causing death. Some of the common ionizing radiation are Gamma rays, X-rays, alpha & beta particles.

  

  • X-rays: They are electromagnetic waves with wavelength smaller than 10nm. X-rays are lethal to mos & higher organisms. However, they are impracticable  for controlling mos because they are expensive to produce, difficult to handle efficiently & since radiations are given off in all directions from the point of origin .However, X-rays are important in producing microbial mutants. (http://en.wikipedia.org/wiki/Mutagenesis)  
  • Gamma rays: They have wavelength of 10^-3  to 10^-2 nm . It is high energy yielding radiation emitted from certain radioactive isotope of Cobalt .Gamma rays are similar to x-rays but of shorter wavelength & high energy. Gamma rays are used in commercial sterilization of materials with high thickness & volume like package of food & medical devices. 
ii) UV Radiation:  It has wavelength between 100 to 400 nm with wavelength 265 nm  is most destructive to bacteria. When mos is subjected to UV light cellular DNA absorbs the energy & form Thymine molecules linked together( thymine dimer) or pyridine dimer. This thymine dimer molecules impairs protein synthesis & replication leading mutation. UV rays are used to reduce microbial population in hospital operating rooms, in aseptic filling rooms, pharmaceutical  industries, food & diary industries & for treatment of contaminated foods.( http://www.rcsb.org/pdb/101/motm.do?momID=91)


iii) Other Radiation:  Ultrasonication( Ultrasonic Vibration) :  They are high frequency sound waves beyond the range of human ears. It is important in fluids as it causes the formation of microscopic bubbles or cavities. Later this cavities collapse & sends out shock waves which ultimately disintegrates the mos in fluid due to external pressure. Though it has few practical application a device called "Sonicator" or "Cavitron"  is used by Dentist to clean teeth. This technique is widely used in research purposes like isolation of sub-cellular structure like antigen, enzymes, toxins,& organelles. It is most effective when used  with an  effective germicide. The above figure shows a Sonicator used by Dentist.  


Comments

Post a Comment

Popular posts from this blog

Stains/ Dyes

STAINS/ DYES      They are colored organic compounds used for staining microorganisms. Chemically, Stains= Benzene ring+ Chromophore+ Auxochrome According to nature of stain, it can be classified into: 1. Acidic Dyes:   It is dye which has negative charge so they bind to positively charged cell structures like some proteins. Acidic dyes are not very often used in Microbiology lab.except to provide background staining like Capsule staining. Examples: Nigrosine, Picric acid, Eosin, Acid fuschin, India ink etc.  2. Basic Dyes:  This dye have positive charge & bind to negatively charged molecules(nucleic acid, -COOH -OH). Since, surface  of bacterial cells are negatively charged(due to Teichoic acid), basic dyes are most commonly used in bacteriology. Examples: Crystal Violet, Methylene Blue, Safranin , basic fuschin. 3. Neutral Dyes:  They are usually formed from precipitation in which are produced when aqueous acidic & basic stains are combined. Neutral dyes stains nuc
Read more

CLINICAL MICROBIOLOGY

Image
3)   Triple Sugar Iron(TSI) Agar Test:                         The TSI agar test  is used to differentiate among the members of the family Enterobacteriaceae and between Enterobacteriaceae and other intestinal bacteria. The authors have chosen three common bacteria in the family Enterobacteriaceae: Escherichia coli, Proteus vulgaris, and Shigella flexneri .  All three are facultatively anaerobic gram-negative rods. In a TSI tube, E. coli produces an acid butt, an acid or alkaline slant, and no H2S, but does produce gas. P. vulgaris produces an acid butt, an acid or alkaline slant, H2S, and gas. S. flexneri produces an acid butt, an alkaline slant, no H2S, and no gas. For the other intestinal bacteria, the authors have chosen Alcaligenes faecalis and Pseudomonas aeruginosa. Both of these intestinal bacteria are gram-negative aerobic rods. In a TSI tube, A. faecalis produces an alkaline butt, alkaline slant, H2S, and gas; P. aeruginosa, an acid butt, alkaline slant, H2S,
Read more

VIROLOGY

Image
VIRUS IDENTIFICATION:    Identifying viral isolates is not an easy task. For one thing, viruses cannot be seen at all without the use of an electron microscope. Serological methods, such as Western blotting, are the most commonly used means of identification. In these tests, the virus is detected and identified by its reaction with antibodies.  Virologists can identify and characterize viruses by using such modern molecular methods as use of restriction fragment length polymorphisms (RFLPs) and the polymerase chain reaction(PCR).PCR PCR was used to amplify viral RNA to identify the west Nile virus in 1999 in the United States & SARS-associated coronavirus in china in 2002. Viral Multiplication:  The nucleic acid in a virion contains only a few of the genes needed for the synthesis of new viruses. These include genes for the virion structural components, such as the capsid proteins, and genes for a few of the enzymes used in the viral life cycle. These enzymes are
Read more