Allelopathic effects of a novel Marinobacter strain (HY-3) on diatom

摘要

We evaluated the allelopathic effects of a novel Marinobacter strain (HY-3, 96% related to M. adhaerens HP15) on a representative diatom (Thalassiosira weissflogii) by determining cell density and chlorophyll a (chl a) of T. weissflogii co-cultured with HY-3 or treated with HY-3 extracellular metabolites. Results showed that the growth of T. weissflogii was significantly inhibited by HY-3 in co-culture at an initial density >= 10(4) cfu/mL. After 10-d cultivation, the relative densities of T. weissflogii co-cultured with HY-3 at initial densities of 10(4), 10(6), and 10(8) cfu/mL were 69%, 23%, and 21% of the control, and the corresponding relative chl a contents were 89%, 61%, and 60% of the control, respectively. The treatment with HY-3 extracellular metabolites had no effects on the growth of T weissflogii. These results indicate that HY-3 is allelopathic to T. weissflogii by inhibiting the growth and photosynthesis of diatom. The allelopathic interactions between these two organisms occurs through the direct contact of cells, rather than the diffusion of extracellular metabolites from the bacterium to the diatom.