<p class="Els-Abstract-text">Some bacteria emits light in the dark. The aim of this research is to find lighting duration and medium composition which produce the most enduring luminescence. The results showed that one of the bacteria isolated from light organ of <em>Loligo duvacelli </em>(D'Orbigny, 1835)<em> </em>squid are able to emit light. The isolation use trisalt solution and cultured into nutrient agar with addition of NaCl emits the longest blue-green light duration under a 1:1 dark-light shift incubation 8.3 d. Meanwhile under a total light, total dark, and in the oven incubator it illuminate for 4.2 d, 3.6 d and 2.6 d, respectively. The combination of beef extract + peptone + a commercial agar + NaCl generate the longest duration of luminescence when incubate in the oven incubator (3,2 d). Meanwhile it illuminated for 2.6 d and 1.7 d on NA + NaCl and NC + NaCl media, respectively, but it failed to illuminate on PCA, NA, and green beans extract + commercial agar + NaCl media. Based on this research we conclude that a commercial agar is potential to replace a technical bacterial agar function.</p><p class="Els-Abstract-text"> </p><div><p class="Els-keywords"><strong>Keywords:</strong> bioluminescence; commercial agar; light treatments; <em>Loligo duvaceli</em> (D'Orbigny, 1835); medium treatment.</p></div>
Laser Spectroscopy and Frequency Stabilization of a Semiconductor Laser for a 87Rb Atomic Clock