Bioluminescent bacterial flora of Nigerian coastal fish species

Abstract

The scarcity of studies on bioluminescent bacteria in fish species along the coastal and marine environment of Nigeria prompted the assessment of abundance of bioluminescent bacteria and possible isolation on three common coastal fish species (Drepane africana, Sardinella maderensis and Mugil cephalus) displaying luminescence. The population of the luminescent bacteria among the three fish species ranged from 2.95×10⁵ to 6.68×10⁶ cfu ml^-1 and the corresponding percentage to the heterotrophic bacteria was between 0.01 and 0.34 %. The surface water had 2.00×10⁵ cfu ml^-1 with 0.20 % ratio to heterotrophic bacteria. The predominant luminescent bacteria observed were gram-negative short rod. Further study of these bacteria showed that growth and light emission occurred concurrently without the exhibition of lag phase; however, maximum luminescence was observed at mid-exponential growth phase suggesting quorum sensing phenomenon. The 16S rRNA gene sequence showed 92.81 % homology to Vibrio campbelli, Vibrio harveyi and Vibrio rotiferianus. This study highlights the occurrence of bioluminescent bacteria in skin of tropical coastal fish species in Nigerian coastal waters and also serves as a fundamental basis for future studies on the biotechnological application of this unique characteristics.