Differential effects of near-UV and visible light on active transport and other membrane processes in Escherichia coli

The effects of monochromatic near-UV and visible light on active transport and several other membrane processes in Escherichia coli were investigated. Using mercury lines at 366, 405, 435, 546 and 578 nm, large differential effects were observed. Transport systems with photosensitive initial rates of uptake were classified into three groups on the basis of wavelength dependence. Three, and possibly four photosensitizers may be involved; three active under aerobic conditions and the fourth in the absence of oxygen. Respiration rate exhibited the same sensitivity as one of the groups, suggesting that the active uptake of member amino acids (e.g. glycine) is largely dependent on oxidation energy. The photosensitivity of glycine transport at 405 nm was not the result of inhibition of the membrane-bound Ca-Mg adenosine triphosphates as shown using an isogenic mutant strain. Cell viability was not affected at the highly active wavelength, 405 nm. Photoeffects on transport of α-methylglucoside were minimal at 366 and 405 nm, contrasting to most of the amino acids investigated. The relative photosensitivity of respiration and several amino acid transport systems depended on carbon source. (author)