Exposure to low doses of UVA increases biofilm formation in Pseudomonas aeruginosa

Abstract

The establishment of bacterial biofilms on abiotic surfaces is a complex process regulated by multiple genetic regulators and environmental factors which are able to modulate the passage of planktonic cells to a sessile state. Solar ultraviolet-A radiation (UVA, 315-400) is one of the main environmental stress factors that bacteria must face at the Earth´s surface. The deleterious effects of UVA are mainly due to oxidative damage. This paper reports that exposure to low UVA doses promotes biofilm formation in three prototypical strains of Pseudomonas aeruginosa, a relevant opportunistic human pathogen. It demonstrates that exposure of planktonic cells to sublethal doses of UVA can increase cell surface hydrophobicity and swimming motility, two parameters known to favor cell adhesion. These results suggest that UVA radiation acts, at least in part, by promoting the first stages of biofilm development.

Keywords:

• Pseudomonas aeruginosa
• ultraviolet-A
• biofilm
• hydrophobicity
• swimming motility

Acknowledgments

The excellent technical assistance of Ms P. Pereyra Schuth is gratefully acknowledged. The authors thank Dr A. Smania and Mic. A. Tobares for providing strain PA14. Financial support for this research was received from the Comisión Nacional de Energía Atómica (Argentina). M.P. is career investigator at Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina).

Disclosure statement

No potential conflict of interest was reported by the authors.