BACKGROUND AND OBJECTIVES In marine environments, luminescent organisms play essential ecological roles and have the potential to offer valuable insights into biotechnological applications. Luminescent bacteria are the most abundant and widely distributed of light-emitting microorganisms. Vibrio and Photobacterium species are the most luminous bacteria. This study aimed to isolate and characterize luminescent bacteria from the unique and ecologically diverse in the Caspian Sea. MATERIALS AND METHODS Samples were collected from 22 areas across the Caspian Sea in north of Iran, encompassing both nearshore and offshore regions. The samples were enriched in SWB liquid medium and incubated at 28 °C for 24 hours, then transferred onto SWA agar for screening of the luminescent bacteria. Luminous colonies were detected in dark room via emission of visible light. These isolates were examined in terms of morphological and physiological tests. Molecular analyses including polymerase chain reaction (PCR) and 16S rRNA gene sequencing were employed to identify the isolated bacteria. RESULTS AND DISCUSSION Preliminary findings indicated that 19 luminescent bacteria were isolated from the Caspian Sea. Among the luminous isolates, MAZ5 and MAZ12 were showed a high emission of visible light. Subsequent analysis of these isolates revealed a diverse array of species, with notable variations in bioluminescent characteristics and genetic profiles. This suggests the existence of distinct luminescent bacteria that have adapted to the specific conditions of the Caspian Sea. CONCLUSION The results of this study demonstrated that a range of luminescent bacteria from the Caspian Sea was isolated. These findings have implications for biotechnological applications, including the development of biosensors and environmental monitoring tools. Overall, this research advances our knowledge of bioluminescence in the Caspian Sea and offers a foundation for future investigations into the ecological significance and potential biotechnological application of these remarkable luminescent bacteria.
