## 4 Discussion  
To identify bacterial genes associated with UVA sensitivity, we constructed a transposon-mutant library and selected mutant strains of _V. parahaemolyticus_ that exhibited high sensitivity to UVA  
Figure 5: Extracellular and intracellular protein content and sensitivity to UVA irradiation among strains with mutations in genes association with general secretion pathways. (**a**,**b**) A typical image of protein content revealed by silver staining after SDS-PAGE. (**a**) Extracellular proteins and (**b**) intracellular proteins were separated as described in the materials and methods section. (**c**) Sensitivity to UVA irradiation, as shown in Figures 2a and 3c. Sensitivities of gene-complemented strains of general secretion pathway genes, p_VP0136/VP0136_ and p_VP0140/_, were also evaluated. Values shown are means \(\pm\) SD (n = 3–5, n = number of independent experimental replicates; **_p_ < 0.01 versus WT. Figure 6: Intracellular ubiquinone-8 concentration and sensitivity to UVA irradiation associated with strains with mutations in ubiquinone biosynthesis genes. (**a**) Mass spectra in the target peak area (white arrow, retention time = 44.8 min) and extracted ion chromatograms (EICs) of ubiquinone-8 (UQ-8, C\({}_{51}\)H\({}_{72}\)O\({}_{2}\), m/z = 727.5665 [M + H]). Gray panel documents the standard curve featuring UQ-8 purified from _Escherichia. Coli_. (**b**) Intracellular concentrations of ubiquinone-8. (**c**) Sensitivity to UVA irradiation. Intracellular UQ-8 was measured by liquid chromatography-time of flight mass spectrometry (LC-TOFMS) as described in the materials and methods section. Values shown are means \(\pm\) SD (n = 3–5, n = number of independent replicates). *_p_ < 0.05 or **_p_ < 0.01 versus WT. irradiation. We selected six mutants that were highly sensitivity to UVA irradiation only, and did not exhibit increased sensitivity to either UVB or UVC. The six selected mutant strains included the mutations in genes encoding F-type H+-transporting ATPase (#78; _VP3069_, #229; _VP3075_), targets in the general secretion pathway (#521; _VP0136_, #358; _VP0140_), and those involved in ubiquinone and other terpenoid-quinone biosynthesis (#2; _VP0097_, #92; _VP0315_). Gene complementation studies performed with these mutant strains resulted in decreased sensitivity to UVA irradiation, approaching levels comparable to the WT. These results suggest that the products of these aforementioned genes serve to regulate sensitivity to UVA irradiation. We previously reported that UVA-LED irradiation increased levels of ROS in _E. coli._ and _V. parahaemolyticus_[14; 19]. In addition, all of the six UVA-sensitive mutants had highly sensitivity to hydrogen peroxide (Supplementary Material Figure S4). These suggest that the genes are associated with the sensitivity to both UVA irradiation oxidative stresses. The enzyme ATP synthase generates ATP from ADP and phosphoric acid via the rotation of the F0 motor on biological membranes with a hydrogen ion concentration gradient [26]. We detected remarkable decreases in intracellular ATP concentrations in the mutant strains _VP3069_ and _VP3075_ that involve the F0F1-type ATP synthase gene; ATP concentrations increased in response to gene complementation (Figure 4a). Although the resistance to UVA irradiation was restored by complementation, the intracellular ATP concentration in the mutants remained lower than that observed in WT cells. [PERSON] et al. [27] reported that intracellular ATP concentrations decreased in response to UVA irradiation and that the concentration was related to resistance against UVA in _E. coli._ Furthermore, [PERSON] et al. [28] reported that the alpha-subunit of the F0F1-type ATP synthase underwent aggregation in response to UVA irradiation. From these results, we conclude that F0F1-type ATP synthase may play an important role in supporting the intracellular ATP concentration during periods of UVA irradiation/stress.