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General Session 3: Biological oceanography & global change |
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Comprehensive insights into antagonistic impacts on diatom
by a bacterium with direct algicidal activity
GS3-25-S
Xueqian Lei* , State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Hongyan Ding, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Xiaoying Zhu, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Yao Chen, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Yi Li, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Wei Zheng, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Hui Wang, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Hong Xu, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Yun Tian, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Tianling Zheng, State Key Laboratory of Marine Environmental Science, School of Life Sciences, Xiamen University, Xiamen, China
Presenter Email: xueqianlei@126.com
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| Interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape ecosystem diversity. Microscale interactions between phytoplankton and bacteria underpin ocean biogeochemistry and frequently involve bacterial chemotaxis to phytoplankton. Understanding interactions between diatom and bacteria is of prime importance to deciphering oceanic nutrient fluxes and biogeochemical cycles. Most reported algicidal bacteria have an inhibitory effect on algal growth by excreting extracellular substances, which is regarded as allelopathy. Few studies have focused on algicidal bacteria inhibited algal growth with direct algicidal activity. Chitinimonas prasina LY03 showed high algicidal effects on ditom Thalassiosira pseudonana, Thalassiosira weissflogii and Skeletonema costatum. In this study, we used the model diatom T. pseudonana to investigate the antagonistic impact in more detail. We found that the bacterial cells showed high algicidal activity, similar to that of the bacterial cultures, while the cell-free supernatant did not show any obvious algicidal activity. The bacterial chemotactic ability and direct interaction characteristic between bacteria and diatom were investigated. The results showed that there was an obvious chemotactic ring in the plate after adding bacterial cells. The levels of cellular pigments, including chlorophyll a and carotenoids, were significantly decreased, which indicated that the LY03 destroyed pigment synthesis. Scanning electron microscope and transmission electron microscopy were used in this study to visualize the interaction between bacterial cells and algae and to reveal alterations in the ultrastructure of T. pseudonana. The algicidal activities of LY03 treatment under low light and dark treatment groups were signifcantly lower than that of the normal light treatment group. The algicidal mechanism were speculated that algicidal bacterial cells chemotaxis to algal cells, and attaches to algal cells, and then produced infochemicals to degrade algal cells, and eventually inducing algal cell death. It is the first time to investigate the interaction between chitinase producing bacteria and diatoms, and this novel special interaction mode was confirmed in this study. This type of antagonistic effect has not, to our knowledge, been previously reported and could have important implications for understanding interaction between bacteria and diatom and ocean biogeochemistry cycles. |
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