I need a procedure for the effect of gamma rays on the bacterial cells?
Gamma radiation is used for sterilization because it kills bacteria. I suppose you are referring to low, sub-lethal doses? What sort of effect were you interested in? DNA breakage, free radical generation, genetic mutation, loss of protein function, growth inhibition...?
The effect you are looking for is a heat. The absorbed dose of gamma rays increases the temperature of irradiated matter and makes the life of bacteria discomfortable.
It´s nearly impossible to irradiate bacteria or other animals with doses that enlarge their temperature significantly. A short example. If you irradiate humans with the so called LD50/30, the supposed dose which kills 50% within 30 days 4.5 Gy whole body dose, the temperature of these individuals just increase ca. 10-3 °C. No cooking at all!
Gamma irradiation of Sulfate Reducing Bacteria in chemically treated produced water:
Different doses of gamma irradiation were applied on SRB within the mixed water, This mixed water contained the optimum concentration of scale inhibitor and sub-lethal concentration of biocides. Only five milliliter of the mixed water transferred to sterile vials purged by nitrogen gas, then exposed to different doses. Gamma irradiation process was carried out in gamma chamber 4000 irradiation facility (manufactured at Bahbha Atomic Research Center India). conducted in 60Co Indian cell located at National Center of Radiation Research & Technology, Nasrcity, Egypt (NCRRT).The dose rate was 0.12 kGy / min. For each treatment as well as control 0 kGy, the bacterial counts were determined in vials Starkey's medium after incubation at 30 oC for 21 days through the MPN technique.
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Bacteria are much much more resistant to irradiation than animals because of many reasons, including, but not limited to, differences in nucleic acid composition, cell wall, metabolism, etc. But most importantly, it is because animals are multicellular. Even in cell survival assays, the surviving fraction is assayed in terms of colonies with 50 cells or more.
In the case of antibiotics, sensitivity assay is done essentially by measuring the distance up to which bacteria growth is inhibited by discs containing the test antibiotic. Later the selected antibiotic can be given to the animal and the it goes every where (of course you will have to ensure its tissue availability and kills the bacteria (bactericidal) or prevents it growth (bacteriostatic). Anticancer drugs are also tested by similar ways.
If you are very particular to test the radiosensitivity of bacteria, you can culture them and irradiate them and if needed you can even place small radioactive sources, just like antibiotics discs. But these will have ABSOLUTELY NO clinical relevance.
The practical application of these Gamma irradiatio (NOT Xray irradiation) is to pass surgical instruments, food, etc. through conveyor belts very close to Cobalt-60 or similar sources. Not economical to use linear accelerators etc. These you can get info from the ISOMED (www.britatom.gov.in/htmldocs/isomed.html) site of BARC or even visit there. It is very impressive place; I have been there
One way you can study is to do a colony count of the bacteria from the sample of a particular instrument or food and do repeat studies afrom samples given different doses of radiation. But DO not forget the PURPOSe of your study
Narayanann Bhattathiri
Yes, thats why sterilisations are performed with typical doses of about 25 kGy.
Gamma rays are a form of ionizing radiation. Their effect is in some ways similar to chemical oxidants (like hydrogen peroxide), but the damage they produce is more spatially clustered. This makes radiation-induced damage to DNA (particularly double strand breaks, DSBs) difficult to repair correctly, causing mutations and/or cell death. Also, radiation damages proteins, lipids and other molecules important for cellular function.
The gamma ray dose needed to kill (sterilize) bacterial cells is typically 100-fold higher, than the dose needed to kill human cells. Some radioresistant bacteria can survive even higher doses, >1000-fold higher than those lethal to human cells. So, to sterilize a bacterial culture with millions-billions of cells, doses of several thousand Gy (kGy) are generally needed (and tens of kGy for the most resistant species). The radioresistance of bacteria is mainly due to small genome size (generally about 1000-fold smaller than the human genome), although the most resistant species (e.g. from genera Deinococcus, Rubrobacter, Geodermatophilus) are particularly well adapted to repair damage to DNA and other important molecules.
Hope this helps
Dear Mohammed,
Gamma radiation induced three types of damage in DNA, single strand
breaks, double strand breaks and nucleotide damage which include base damage and
damage in the sugar moiety. The base damage is a major component of damage
induced by ionizing radiation. Gamma irradiation also affects protein fingerprinting and enzymes.
source: https://www.researchgate.net/publication/273449874_The_Effect_of_Ionizing_Radiation_on_Multi-drug_Resistant_Pseudomonas_aeruginosa_Isolated_from_Aquatic_Environments_in_Egypt
Article The Effect of Ionizing Radiation on Multi-drug Resistant Pse...
I believe that 10 to 50 kGy total dose will have destructive effect on the DNA.
Radiation response of bacteria has been well studied of which radiosensitiviry varies very widely from sensitive to resistant. The typical example of radioresistant bacteria includes Deinococcus radiodurans.
I would recommend to have a MC simulation using DNA package from GEANT4 - DNA.
It would be give an analytical output for bacterial DNA damage under a Gamma ray flux.
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