Genome-wide transcriptional response of Escherichia coli O157:H7 to light-emitting diodes with various wavelengths.

We investigated the physiological and transcriptomic response of Escherichia coli at the early stationary phase to light-emitting diodes with different wavelengths. The growth and metabolic changes of E. coli O157:H7 were examined under the influence of 465, 520, and 625 nm illuminated light. Under 465 nm illumination, the growth of E. coli O157:H7 was significantly retarded compared to 520 nm and 625 nm illumination and non-illuminated control. Metabolic changes were examined under these illumination and non-illuminated conditions based on transcriptomic reads. Transcriptomic response under 520 nm and 625 nm remained almost similar to control except few up-and down-regulated genes. Carbohydrates metabolic transcriptomic reads were greatly down-regulated under 465 nm illumination compared to 520 nm and 625 nm illumination and non-illuminated control showing depletion of glucose as a sole energy source during the exponential phase. Fatty acid degradation such as fad regulon-related genes was up-regulated in cells under 465 nm illumination revealing the shifting of cells to use fatty acid as a new carbon energy source during the early stationary phase. Exposure of E. coli O157:H7 cells to 465 nm illuminated light down-regulated virulence factor genes such as hlyA, hlyB, hlyC, stx1A, stx2B, paa, and bdm. Under the stress of 465 nm illumination, expression of stress and flagellar motility-related genes were up-regulated causing consumption of energy and reduction in cell growth. Also, oxidative phosphorylated transcriptomic reads were up-regulated under 465 nm illumination probably due to the production of ROS that might involve in the reduction of cell growth during the early stationary phase. These results indicate that pathogenic E. coli O157:H7 respond differentially to a different wavelength of the light-emitting diodes used in this study.