Confocal micro-Raman Spectra of untreated and lethally treated Escherichia coli exposed to UV-B and violet light

TL;DR

This study investigates how UV-B and violet light exposure cause specific chemical and structural changes in live E. coli bacteria, as observed through confocal micro-Raman spectroscopy, revealing different damage mechanisms based on photon energy.

Contribution

It provides detailed Raman spectral analysis of E. coli's molecular changes after lethal UV-B and violet light exposure, highlighting energy-dependent damage pathways.

Findings

UV-B causes significant DNA/RNA bond disruption.

Violet light induces protein and lipid modifications.

Different photon energies lead to distinct bacterial damage mechanisms.

Abstract

We report on changes in the Raman spectrum of live Escherichi coli (E.coli) that result from exposure to lethal fluences of 300 nm (UV-B) and 405 nm (violet) photons. In the first instance, the energy per photon of 4.13 eV is sufficient to break most of the inter-atomic bonds in the bacterium and major change in the Raman spectrum, particularly in the RNA/DNA regions is observed. This energy is in near resonance with the C-H, N-H, and P-O bond binding energies that interconnect phosphate backbone sections and may initiate the Raman modifications. By contrast, the 3.06 eV violet photon energy is insufficient to cleave the stronger system bonds. The much larger lethal fluence required in this case produces a significant change in the resonant C-N and C-P bond connected amino acid/protein groups and lipid peak signal but much less so in the nucleotide-DNA/RNA signature.