Bacterial photoprotection through extracellular cadmium sulfide crystallites

Justin D. Holmes, Peter R. Smith, Richard Evans-Gowing, David J. Richardson, David A. Russell, John R. Sodeau

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18 Citations (Scopus)


Ultraviolet light and the heavy metal, cadmium, both have toxic effects on many microorganisms. In this communication we describe a method by which the bacterium Klebsiella aerogenes surmounts both problems using one biological process: the synthesis of cadmium sulfide (CdS) crystallites. These semiconductor particles absorb radiation in the UV spectral region and therefore, when K. aerogenes produces extracellular CdS material in response to environments containing cadmium ions, a photoprotective layer is formed. The effect of UVA radiation on cultures of Klebsiella aerogenes was monitored using electron microscopy, energy‐dispersive X‐ray analysis and electronic spectroscopy. The results show that at wavelengths 320 nm Λ 400 nm, a photoprotection period of between 4 and 6 h is induced, which eventually fails due to photodegradation of the semiconductor layer to metallic cadmium and elemental sulfur.

Original languageEnglish
Pages (from-to)1022-1026
Number of pages5
JournalPhotochemistry and Photobiology
Issue number6
Publication statusPublished - Dec 1995

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