I think the main assumption is DNA damage, or that's at least the best studied one. One of the best-known effects of UV radiation on DNA is the formation of pyrimidine dimers which mess up the structure of double stranded DNA.

However, if I remember right, UV irradiation can also damage lipids by oxidation and to a lesser extent, damages proteins, so it could be all of the above.

I think the main assumption is DNA damage, or that's at least the best studied one. One of the best-known effects of UV radiation on DNA is the formation of pyrimidine dimers which mess up the structure of double stranded DNA.

However, if I remember right, UV irradiation can also damage lipids by oxidation and to a lesser extent, damages proteins, so it could be all of the above.

Hello David,

I agree with Alexandra Johnson.

UV irradiation breaks the hydrogen bond between adenine and thymine of DNA. Forms a covalent bond between the thymine groups. The new covalent bond is much stronger than the hydrogen bond it replaces. Prevents the DNA replication process that is needed to create proteins. Thus reproduction of the microbe stops. Bacteria have a typical lifetime of only a few minutes, and so it is rendered harmless.

Thank you for your enlightening answers.

Does the effect mentioned above by Monjurul occur in all cells exposed to UV light, including our skin and retinal cells?

UV radiation causes the formation of lethal thymine dimers on bacterial DNA. It has been demonstrated that UV is effective in killing microorganisms contaminating the surfaces of a variety of materials.

- Pseudomonas, Streptococcus, Acanthamoeba, Candida, and Aspergillus cells on contact lenses were killed within 20 min of UV treatment.

- Wallner-Pendleton et al. suggested that UV radiation can reduce Salmonella surface contamination without negatively affecting poultry carcass color or increasing the rancidity of the meat.

- Gao et aI. reported that UV radiation can significantly decrease the number of Salmonella cells inoculated on the surface of eggshells, plastic belt, fiber belt, and metal.

- Goerzen and Scott found that the microbial scores from eggshell surfaces were significantly reduced after 5 s of exposure to UV light.

-UV-C light is usually used for reducing the initial concentration of the food poisoning germs existing on the surface of vegetables, fruits. UV-C destroys the base sequence of bacterial DNA and it causes bactericidal action

(Sizer and Balasubramaniam, 1999).

- The wavelength for UV processing ranges from 100 to 400 nm. The wavelength between 220 and 300 nm is considered germicidal against microorganism such as bacteria, viruses, and yeasts(Bintsis et al., 2000). The highest germicidal effect is obtained between 250 and 270 nm (UVC)(Bachmann,1975).

- UV showed a good reductive effect on the three pathogens in the following descending order: E. coli O157:H7 > L. monocytogenes > S. Typhimurium.

David,

Alexander, Mizan and Monjurul has all given you wonderful explanations, basically, its results in DNA Damage and the target is the thymine nucleotides in the DNA.The Ultraviolet light initiates the reaction between two molecules of thymine which results in thymine dimer that is very stable so auto repair is difficult without the aid of excising or removing the two bases and filling in the gaps with new nucleotides.

What about the bacteria growth rate after exposing to UV spectrometer for optical density measurement. Is that UV light effect the bacteria growth? specifically when keep using the same culture.

Ultraviolet (UV) light prevent the growth of bacteria by damaging their DNA.

https://www.quora.com/Why-does-UV-ultraviolet-light-kill-bacteria

It's also effect protein secondary structure when ormatic amino acids absorb uv light.