Isolation and algicidal characterization of Bowmanella denitrificans S088 against Chlorella vulgaris

One strain of algicidal bacterium, named as S088, was isolated from the intestine of healthy sea cucumbers (Stichopus horrens) in the South China Sea. Based on the analysis of its biochemical characteristics and 16S rDNA gene sequence, S088 was identified as Bowmanella denitrificans. Importantly, the algicidal activity of S088 on Chlorella vulgaris was characterized in this study. The initial densities of bacterial and algal cell showed strong influence on the removal rates of chlorophyll a. When the strain S088 was cultured under a complete darkness condition at 30 °C, its algicidal activity reached the highest level. Furthermore, it was found that the filtered supernatant from bacterial cultures had full algicidal activity, suggesting that the secreted compounds from S088 are involved in the observed algicidal action of S088. Moreover, the algicidal compounds were heat tolerant and had no cytotoxicity against fish cells, indicating that S088 would have a promising application as a safe probiotics for S. horrens. Finally, this is the first report about the algicidal activities in B. denitrificans.