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Related Experiment Video

Updated: Jun 19, 2026

Inactivation of Pathogens via Visible-Light Photolysis of Riboflavin-5′-Phosphate

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Published on: April 6, 2022

THE ABIOTIC ACTION OF ULTRA-VIOLET LIGHT.

¹Laboratory of the Henry Phipps Institute of the University of Pennsylvania, Philadelphia.

The Journal of Experimental Medicine

|October 30, 2009

Summary

Typhoid bacilli exhibit limited sensitivity to ultraviolet light between 2100-2800 Angström units. Their sensitivity rapidly diminishes to near zero around 2970 Angström units.

Area of Science:

Microbiology
Photobiology

Background:

Ultraviolet (UV) light has germicidal properties.
Understanding the specific UV sensitivity of pathogenic bacteria is crucial for disinfection applications.

Purpose of the Study:

To quantify the sensitivity of typhoid bacilli to specific ultraviolet light wavelengths.
To compare the UV sensitivity of typhoid bacilli to a known standard (photographic plate).

Main Methods:

Exposure of typhoid bacilli to ultraviolet light across a spectrum of wavelengths.
Quantitative assessment of bacterial inactivation.
Comparison with the photosensitivity of a standard photographic plate.

Main Results:

Typhoid bacilli demonstrated approximately 1/200th the sensitivity of a photographic plate to UV light between 2100-2800 Angström units.

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Bacterial sensitivity decreased sharply above 2800 Angström units, reaching negligible levels near 2970 Angström units.

Conclusions:

Typhoid bacilli are relatively resistant to germicidal UV wavelengths compared to photographic materials.
The optimal germicidal range for typhoid bacilli appears to be within the 2100-2800 Angström unit spectrum, with effectiveness rapidly declining beyond this range.