Abstract
Harmful algal blooms (HABs) cause a variety of deleterious effects on aquatic ecosystems, especially the toxic dinoflagellate Alexandrium tamarense, which poses a serious threat to marine economic and human health based on releasing paralytic shellfish poison into the environment. The algicidal bacterium Deinococcus sp. Y35 which can induce growth inhibition on A. tamarense was used to investigate the functional mechanism. The growth status, reactive oxygen species (ROS) content, photosynthetic system and the nuclear system of algal cells were determined under algicidal activity. A culture of strain Y35 not only induced overproduction of ROS in algal cells within only 0.5 h of treatment, also decrease the total protein content as well as the response of the antioxidant enzyme. Meanwhile, lipid peroxidation was induced and cell membrane integrity was lost. Photosynthetic pigments including chlorophyll a and carotenoid decreased along with the photosynthetic efficiency being significantly inhibited. At the same time, photosynthesis-related gene expression showed down-regulation. More than, the destruction of cell nuclear structure and inhibition of proliferating cell nuclear antigen (PCNA) related gene expression were confirmed. The potential functional mechanism of the algicidal bacterium on A. tamarense was investigated and provided a novel viewpoint which could be used in HABs control.
Highlights
Harmful algal blooms (HABs), which almost always destroy the stability of marine ecosystem and damage other marine organisms (Zhang et al, 2014), have broken out more and more frequently in recent years (Anderson et al, 2012)
We studied the Fv/Fm value when adding DCMU, and the result showed that the Fv/Fm value was inhibited compared to the control (Figure 6A, inset), which implied that the algicidal bacteria had a similar function with DCMU, and could inhibit the photosynthetic efficiency of the algal cells
Algicidal bacteria have been studied for years as one of the most safety and effective ways to implement HAB bio-control (Imai et al, 1993; Skerratt et al, 2002; Mayali and Azam, 2004), but the functional mechanism is still not clear
Summary
Harmful algal blooms (HABs), which almost always destroy the stability of marine ecosystem and damage other marine organisms (Zhang et al, 2014), have broken out more and more frequently in recent years (Anderson et al, 2012). Alexandrium tamarense belongs to toxic dinoflagellate, which can secrete paralytic shellfish poison, and always form HABs (Zhang et al, 2013). As primary producers of the seas and oceans, can be fed by protozoan or other organisms, the. Algal death mechanism induced by bacteria dinoflagellate toxin can pass through the food chain and accumulate in organism at the higher trophic levels, and threaten human health (Li et al, 2015). There are many measures including physical and chemical methods to inhibit HABs (Li et al, 2011; Lee et al, 2013), but these traditional methods are high cost, hard to perform, and especially hazardous to other harmless organisms (Li and Pan, 2013), so biological methods with a reputation for secure and efficient use have been chosen as novel HAB-control methods of regulating blooms (Jeong et al, 2008; Chen et al, 2014)
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