Marine bacteria play an important role in the marine nutrition cycles. About half of all sea-living bacteria can use light as an energy source, in addition to organic carbon compounds, which is important for survival as the seas becomes acidic and low in nutrition due to changing climate. The Flavobacteriaceae is a bacterial family that plays an important role in the degradation of complex organic compounds in natural environments. Dokdonia donghaensis MED134 belongs to the Flavobacteriaceae family and use both chemotrophy and phototrophy as a source of energy. For its phototrophic ability, the bacteria use proteorhodopsin, which is a membrane-bound proton pump. This allows the bacteria to survive and grow in nutrient-poor environments. The purpose of the study was to investigate with qPCR if there was a difference in gene expression for proteorhodopsin and isocitrate dehydrogenase in Dokdonia donghaensis MED134 depending on whether the bacteria had grown in constant light or darkness. Analysis with qPCR showed a significantly greater gene expression for proteorhodopsin in the bacteria grown in constant light for seven days, compared to those grown in constant light for three and four days and those grown in constant darkness. No significant difference could be demonstrated in gene expression for isocitrate dehydrogenase. This indicates that Dokdonia donghaensis MED134 in nutritional deficiency can use light as a source of energy for survival and further growth. By simulating climate change an adaptability could be seen through increased gene expression. Through this, further understanding of the role of bacteria in the marine ecosystem can be obtained and further research can be conducted as the marine climate issue becomes more relevant.