Effects of a pulsed light-induced stress on Enterococcus faecalis

Area of Science:

• Microbiology
• Food Science
• Biotechnology

Background:

• Pulsed light (PL) is a surface decontamination method for food, packaging, and water.
• PL effectiveness can be limited by low penetration and shadow effects, allowing bacteria to survive and perceive PL as a stress.
• Enterococcus faecalis is a highly adaptable environmental bacterium.

Purpose of the Study:

• To investigate the effects of low-energy pulsed light (PL) stress on Enterococcus faecalis V583.
• To understand the adaptive mechanisms and molecular responses of E. faecalis to PL treatment.
• To assess the impact of PL pre-treatment on bacterial resistance and mutation frequency.

Main Methods:

• Mimicking PL stress using low transmitted energy conditions.
• Artificially inoculating a medium and applying varying PL doses (0.5 to 1.8 J cm⁻²).
• Performing global proteome analysis to identify changes in protein abundance.

Main Results:

• Complete decontamination was achieved at 1.8 J cm⁻², with significant log reductions at lower doses (0.5–1.2 J cm⁻²).
• A 0.5 J cm⁻² PL pre-treatment enhanced E. faecalis resistance to a subsequent 1.2 J cm⁻² dose.
• Low-energy PL treatment increased bacterial mutation frequency and altered the abundance of 19 proteins.

Conclusions:

• Enterococcus faecalis demonstrates adaptive capabilities to pulsed light stress.
• A molecular response to low-energy PL leads to increased resistance and mutation frequency.
• The study provides insights into E. faecalis stress resistance mechanisms.