Metaproteomics of marine viral concentrates reveals key viral populations and abundant periplasmic proteins in the oligotrophic deep chlorophyll maximum of the South China Sea.

Viral concentrates (VCs), containing bioinformative DNA and proteins, have been used to study viral diversity, viral metagenomics and virus-host interactions in natural ecosystems. Besides viruses, VCs also contain many noncellular biological components including diverse functional proteins. Here, we used a shotgun proteomic approach to characterize the proteins of VCs collected from the oligotrophic deep chlorophyll maximum (DCM) of the South China Sea. Proteins of viruses infecting picophytoplankton, that is, cyanobacteria and prasinophytes, and heterotrophic bacterioplankton, such as SAR11 and SAR116, dominated the viral proteome. Almost no proteins from RNA viruses or known gene transfer agents were detected, suggesting that they were not abundant at the sampling site. Remarkably, nonviral proteins made up about two thirds of VC proteins, including overwhelmingly abundant periplasmic transporters for nutrient acquisition and proteins for diverse cellular processes, that is, translation, energy metabolism and one carbon metabolism. Interestingly, three 56 kDa selenium-binding proteins putatively involved in peroxide reduction from gammaproteobacteria were abundant in the VCs, suggesting active removal of peroxide compounds at DCM. Our study demonstrated that metaproteomics provides a valuable avenue to explore the diversity and structure of the viral community and also the pivotal biological functions affiliated with microbes in the natural environment.

[Advances and Prospect of Sampling Techniques and Analytical Methods for Trace Elements in the Ocean: Progress of Trace Element Platform Construction in Xiamen University].

Trace elements, which are important chemical components in the ocean, generally refer to those chemical elements with concentrations below 10 µmol·kg-1in seawater. Some trace elements, such as Fe and Zn, serve as essential micronutrients for marine organisms, which regulate marine primary productivity and are closely related to the biogeochemical cycle of carbon and nitrogen and therefore affect the global environment and climate change. In contrast, some elements, such as Pb, are anthropogenic pollutants largely released by human activities. In addition, some trace elements and their isotopes can be used as tracers for oceanographic processes and proxies for paleoceanography. However, the high saline matrix and extremely low trace element concentrations in seawater, as well as the contamination from research vessels, sampling equipment, and the surrounding environment during the process of sample collection, pretreatment, and analysis, have restricted researchers from obtaining reliable trace element data in the ocean for a long period of time. Nevertheless, high quality samples and accurate data are prerequisites for investigating the biogeochemical and environmental behavior of marine trace elements. This paper reviews the development of sampling techniques and analytical methods for trace elements in seawater, introduces the research history and platform construction activities in Xiamen University in this field, summarizes the advantages and disadvantages of various sampling and analytical techniques and methods, and presents the perspectives on future developments in the research on trace elements in the ocean.

[Spatial distribution of seawater dimethylsulfide in winter of Jiulong Jiang Estuary].

Cruise investigation of dimethylsulfide (DMS) emission in estuarine areas, heavily disturbed by human activities, was carried out in the winter of 2001 in Jiulong Jiang Estuary. The concentrations of chlorophyll, salinity and nutrients showed evidently spatial distribution in Jiulong Jiang Estuary, so did DMS concentrations in surface water. The average of seawater DMS was 101.0 and 242.1 ng x L(-1) in river mouth area and gulf area, respectively. DMS concentrations decreased first with the increase of seawater salinity and then increased. The highest DMS concentration occurred at river plume front of maximum turbidity zone of the estuary.