UVGI destroys microorganisms by destroying their DNA. Which is true about this statement?

• A. True
• B. False
• C. Only bacteria
• D. Only viruses

Answer: (A)

UVGI inactivates microorganisms by damaging their genetic material. UV-C light is absorbed by nucleic acids and forms pyrimidine dimers (most commonly thymine dimers in DNA), which distort the DNA and prevent replication and transcription. Without the ability to replicate, the organism can’t propagate, so it is effectively destroyed or inactivated. This mechanism primarily targets genetic material, so bacteria (with DNA) are inactivated this way, and many viruses are inactivated as well by damaging their DNA or RNA genomes. While the statement emphasizes DNA, it’s important to note that RNA genomes in RNA viruses can also be damaged by UV-C, leading to inactivation. In short, UVGI destroys microorganisms by compromising their genetic material, which is the foundation of its germicidal effect.