Homeophasic Adaptation in Response to UVA Radiation in Pseudomonas aeruginosa: Changes of Membrane Fatty Acid Composition and Induction of desA and desB Expression

• Published in: Photochemistry and photobiology 2022-07, Vol.98 (4), p.886-893
• Main Authors: Pezzoni, Magdalena, De Troch, Marleen, Pizarro, Ramón A., Costa, Cristina S.
• Format: Article
• Language: English
• Subjects: Adaptation; Bacteria; Composition; Desaturase; Desaturation; Earth surface; Environmental changes; Environmental conditions; Fatty acid composition; Fatty acids; Fluidity; Membrane fluidity; Membranes; Phospholipids; Pseudomonas aeruginosa; Radiation; Ultraviolet radiation; Viscosity
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/php.13548

ABSTRACT In bacteria, exposure to changes in environmental conditions can alter membrane fluidity, thereby affecting its essential functions in cell physiology. To adapt to these changes, bacteria maintain appropriate fluidity by varying the composition of the fatty acids of membrane phospholipids, a phenomenon known as homeophasic adaptation. In Pseudomonas aeruginosa, this response is achieved mainly by two mechanisms of fatty acid desaturation: the FabA–FabB and DesA–DesB systems. This study analyzed the effect of ultraviolet‐A (UVA) radiation—the major fraction of solar UV radiation reaching the Earth's surface—on the homeophasic process. The prototypical strain PAO1 was grown under sublethal UVA doses or in the dark, and the profiles of membrane fatty acids were compared at early logarithmic, logarithmic and stationary growth phases. In the logarithmic growth phase, it was observed that growth under sublethal UVA doses induced the expression of the desaturase‐encoding genes desA and desB and increased the proportion of unsaturated fatty acids; in addition, membrane fluidity could also increase, as suggested by the indices used as indicators of this parameter. The opposite effect was observed in the stationary growth phase. These results demonstrate the relevant role of UVA on the homeophasic response at transcriptional level. The effect of UVA radiation was analyzed on the homeophasic adaptation in Pseudomonas aeruginosa. The strain PAO1 was grown under sublethal UVA doses or in the dark, and the profiles of membrane fatty acids and the expression of desaturases coding genes fabA, desA and desB was analyzed. In the logarithmic growth phase, the exposure to UVA increased the expression of desA and desB, the proportion of unsaturated fatty acids and the membrane fluidity; the opposite was observed in the stationary growth phase. This study demonstrates the relevant role of UVA on the homeophasic response at the transcriptional level.