The Transcriptional Repressor PerR Senses Sulfane Sulfur by Cysteine Persulfidation at the Structural Zn2+ Site in Synechococcus sp. PCC7002.

Cyanobacteria can perform both anoxygenic and oxygenic photosynthesis, a characteristic which ensured that these organisms were crucial in the evolution of the early Earth and the biosphere. Reactive oxygen species (ROS) produced in oxygenic photosynthesis and reactive sulfur species (RSS) produced in anoxygenic photosynthesis are closely related to intracellular redox equilibrium. ROS comprise superoxide anion (O2●-), hydrogen peroxide (H2O2), and hydroxyl radicals (●OH). RSS comprise H2S and sulfane sulfur (persulfide, polysulfide, and S8). Although the sensing mechanism for ROS in cyanobacteria has been explored, that of RSS has not been elucidated. Here, we studied the function of the transcriptional repressor PerR in RSS sensing in Synechococcus sp. PCC7002 (PCC7002). PerR was previously reported to sense ROS; however, our results revealed that it also participated in RSS sensing. PerR repressed the expression of prxI and downregulated the tolerance of PCC7002 to polysulfide (H2Sn). The reporter system indicated that PerR sensed H2Sn. Cys121 of the Cys4:Zn2+ site, which contains four cysteines (Cys121, Cys124, Cys160, and Cys163) bound to one zinc atom, could be modified by H2Sn to Cys121-SSH, as a result of which the zinc atom was released from the site. Moreover, Cys19 could also be modified by polysulfide to Cys19-SSH. Thus, our results reveal that PerR, a representative of the Cys4 zinc finger proteins, senses H2Sn. Our findings provide a new perspective to explore the adaptation strategy of cyanobacteria in Proterozoic and contemporary sulfurization oceans.

The Effect of Domestic Sewage Treatment on Islands Using Ecological Treatment Processes: A Case Study of Haimen Island, Fujian Province.

Islands are characterized by a lack of land and freshwater resources, public finances, and technical personnel. As a result, domestic sewage may not be effectively treated, which can lead to major pollution on islands and in the surrounding sea areas. In this study, a pilot treatment of domestic sewage was conducted using an ecological treatment process (i.e., a constructed wetland and ecological pond) in an abandoned pond located on Haimen Island, Fujian Province, China. The pollutant indicators were monitored to analyze this treatment method at different treatment stages. The results showed that the combination of multiple ecological treatment processes had favorable treatment effects on various pollutants in the sewage. The treatment rates of the chemical oxygen demand (CODCr) and suspended solids (SS) surpassed 88%. The treatment rate of the biochemical oxygen demand (BOD5), ammonia nitrogen (NH3-N), total nitrogen (TN), total phosphorus (TP), and fecal coliform surpassed 93%, and all the indicators met or were close to the level I B emission standards for urban sewage treatment plants. Different treatment stages have different treatment effects on different pollutants. The constructed wetland played an important role in sewage treatment through plant absorption, substrate adsorption, sedimentation, and microbial decomposition, particularly for the TP, CODCr, and BOD5. In contrast, algal photosynthesis in the ecological pond produced a large amount of dissolved oxygen, and the treatment effect was highest for the TN and NH3-N. The treatment effects on the fecal coliform in the constructed wetland and ecological pond were very significant. Ecological treatment processes based on the combination of a constructed wetland and ecological pond have favorable treatment effects, low construction and maintenance costs, and pollution-free conditions, which are suitable for application in island areas.

Distribution Characteristics and Restoration Application of Vegetation in Chengcun Bay Surrounding Areas of Yangjiang City.

In recent years, global warming and sea level rise have further aggravated the risk of coastal erosion. Coastal vegetation plays an important role in resisting storm surges and alleviating coastal erosion. Therefore, screening plant species for the purpose of constructing ecological seawalls to protect or repair damaged coastal zones has become a hot issue. In this paper, a field survey was conducted to investigate the vegetation in Chengcun Bay surrounding areas of Yangjiang City by combining a line survey and sample plot survey. By understanding the vegetation types, distribution and community structure in the bay's surrounding areas and analyzing the restricting environmental factors of those plants, we put forward some countermeasures for coastal vegetation restoration in difficult site conditions from the aspects of plant species selection, vegetation configuration and restoration technology, so as to provide reference for ecological vegetation restoration in similar locations.

Carbon Sequestration in the Form of Recalcitrant Dissolved Organic Carbon in a Seaweed (Kelp) Farming Environment.

Under climate change scenarios, the contribution of macroalgae to carbon sequestration has attracted wide attention. As primary producers, macroalgae can release substantial amounts of dissolved organic carbon (DOC) in seawater. However, little is known about the molecular composition and chemical properties of DOC derived from macroalgae and which of them are recalcitrant DOC (RDOC) that can be sequestered for a long time in the ocean. In the most intensive seaweed (kelp) farming area (Sanggou Bay) in China, we found that kelp mariculture not only significantly increased DOC concentration, but also introduced a variety of new DOC molecular species, many of which were sulfur-containing molecules. A long-term DOC degradation experiment revealed that those DOC with strong resistance to microbial degradation, i.e., RDOC, account for approximately 58% of the DOC extracted from kelp mariculture area. About 85% (3587 out of 4224 with different chemical features) of the RDOC molecular species were steadily present throughout the long-term degradation process. 15% (637 out of 4224 with different chemical features) of the RDOC molecular species were likely newly generated by microorganisms after metabolizing macroalgae-derived labile DOC. All these stable RDOC should be included in the blue carbon budgets of seaweed.

Analysis of the characteristics of Eco-Exergy-based indices and diversity indices in the Zhoushan archipelago, China.

Anthropogenic disturbance of coastal ecosystems has increased the need for comprehensive methods and indicators to assess the health status of marine ecosystems. Biotic indices are important as they indicate different ecological states. In this study, Eco-Exergy-based indices (Exergy and Structural Exergy) and diversity indices (Shannon-Wiener index and Margalef index) were applied in the seas around the Zhoushan archipelago, and correlation analysis between biotic indices and environmental factors was used to test the robustness of these indices in capturing the environment changes, aimed to provide reference in selecting the indices for assessing marine eco-environment quality. Results showed that the benthic indices of Exergy, Shannon-Wiener, and Margalef increased with the distance from the mainland. The Eco-Exergy-based indices and Margalef index were significantly, negatively correlated with dissolved inorganic nitrogen and reactive phosphate, and significantly, positively correlated with the salinity of seawater. Overall, the marine ecosystem was more stable further away from the coast, where salinity was higher, and pollutants such as nutrients in seawater were lower. In addition, biodiversity and Eco-Exergy was also higher. Generally, Eco-Exergy-based indices were observed to be good indicators for detecting the environment changes in the study area.

[Spatial Variation of Ammonia-N, Nitrate-N and Nitrite-N in Groundwater of Dongshan Island].

In Dongshan Island, groundwater is the main resource of the local residents' drinking water, domestic water, agriculture irrigation and freshwater aquaculture. This study aimed to investigate the spatial distribution characteristic and its variation pattern of ammonia-N, nitrate-N and nitrite-N in groundwater, as well as its pollution source and influence factors. It is very important to understand the pollution level of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island, the control and prevention of ammonia-N, nitrate-N and nitrite-N pollution, which is of great significance to the residents' health. In this study, the spatial variability characteristics of ammonia-N, nitrate-N and nitrite-N concentration in groundwater of Dongshan Island was analysed by geo- statistic method, the values of the non-observation points were determined by Kriging method, and the pollution characteristics of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island was also analyzed. Our results showed that the ammonia-N and nitrite-N concentration in groundwater of Dongshan Island were at low levels, but their spatial variability were high, and their autocorrelation were poor; however, the nitrate-N concentration was general high, its spatial variability was moderate, and the autocorrelation was much good. The distribution characteristics of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island were similar that the high concentration areas were all located in the coastal land. The domestic pollutants and human and animal wastes from towns and villages were the main sources of nitrogen pollution, which would be the first step to control the nitrogen pollution of Dongshan Island. Land use pattern, soil type, groundwater depth, pH, dissolved oxygen, season, and the existence of Fe2+, were the impact factors that influence the distribution and transformation of ammonia-N, nitrate-N and nitrite-N in groundwater, which could be the considerable factors in the control of nitrogen pollution in groundwater of Dongshan Island.