Distinct taxonomic and ecological functions of microbiome in sediments of different depth in Bohai Sea and Yellow Sea

Microorganisms in sediments are critical to marine ecosystems.The microbial communities in marine sediments of the Bohai Sea(BS)and Yellow Sea(YS),the eastern Chinese marginal seas,were uncovered in employing the metagenomic approach.In addition,the taxonomic and functional compositions of microbes were compared among various sediment core depths.Results showing the compositions,diversities,and functions of the microbial communities showed no significant variations with sea areas,and significant seasonal variations was observed in station 3500-7 only on functions of the microbial communities.Moreover,the compositions,diversities,and functions of the microbial communities changed noticeably in different sediment depths in close correlation with physical and chemical properties of sediments.However,the large fraction of the variation in functional communities remained unexplained.From bioinformatic analysis of the metagenomic data,the carbon-metabolismrelated genes such as glycosyl transferase(GT),glycoside hydrolase(GH),and carbohydrate esterase(CE)genes were rich in the microbial community,especially in the top sediment depth.Additionally,in this N-polluted habitat,nitrification and anaerobic ammonia oxidation(anammox)were dominant in the top sediment depth,whereas dissimilatory nitrate reduction to ammonium(DNRA)and denitrification were dominant in the middle and bottom depth,respectively.Further identification of possible biogeochemical links suggested that Gammaproteobacteria,Alphaproteobacteria,Nitrospirae,Nitrospinae,Chloroflexi,and Methanomicrobia might promote effective circulation of carbon and nitrogen cycling.This study expanded our knowledge about the structure and functional potential of microbial communities associated with different sediment depth,and provided further comprehensive information on element cycles in marine environments.

Microbial community coexisting with harmful alga Karenia mikimotoi and microbial control of algal bloom in laboratory

Algicidal bacteria have been frequently isolated from algal blooming areas.However,knowledge regarding the microbial communities coexisting with microalgae and their potential application in preventing harmful algal blooms(HABs)is limited.In this study,we investigated the composition of the microbial community coexisting with harmful alga Karenia mikimotoi and its responses to algal control via nutrient stimulation or by adding algicidal strain in microcosms.The microorganisms inhabiting the K.mikimotoi culture consisted of 24 identifi ed phyla,including dominant Proteobacteria(relative abundance 76.24%±7.28%)and Bacteroidetes(22.67%±8.32%).Rhodobacteraceae,Phaeodactylibacter,and Maritimibacter predominated during the algal cultivation.Both the added nutrient and fermentation broth of algicidal strain Pseudoalteromonas QF1 caused a massive death of K.mikimotoi and substantial changes in the coexisting microbial community,in which Rhodobacteraceae and Phaeodactylibacter signifi cantly decreased,while Halomonas and Alteromonas increased.Core operational taxonomic units(OTUs)analysis indicated that 13 OTUs belonging to Rhodobacteraceae,Maritimibacter,Marivita,Nisaea,Phaeodactylibacter,Citreicella,Halomonas,Alteromonas,Marinobacter,Muricauda,and Pseudoalteromonas dominated the changes of the microbial communities observed in the K.mikimotoi culture with or without treatments.Collectively,this study indicated that microbial community inhabiting K.mikimotoi culture includes potential algicidal bacteria,and improves our knowledge about microbial community succession during biocontrol of K.mikimotoi via nutrient stimulation or by adding isolated algicidal strains.

Novel antibody epitopes dominate the antigenicity of spike glycoprotein in SARS-CoV-2 compared to SARS-CoV

Recently,the World Health Organization(WHO)has declared the novel coronavirus(2019-nCoV)outbreak a Public Health Emergency of International Concern(PHEIC),1 which is now formally named as severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).2 As of 27 February 2020,a total of 82,178 cases of SARS-CoV-2 infection have been confirmed across the world,with 78,630 cases in China(https://ncov.dxy.cn/ncovh5/view/pneumonia?source=).The SARSCoV-2 has been determined as the seventh member of the coronaviruses infected humans.3 Moreover,similar to severe acute respiratory syndrome coronavirus(SARS-CoV)and Middle East respiratory syndrome coronavirus(MERS-CoV),the SARS-CoV-2 could also cause severe and fatal illness.3 Since the SARS-CoV-2 outbreak,there have been approximately 14,792 clinically severe cases and 2800 dead cases.

Anaphthalimide-based fluorescent probe for mercapto-containing compounds

A polarity-sensitive fluorescent probe MNP was rationally designed and synthesized with naphthalimide as the fluorophore and maleimide as the receptor for thiols. MNP is weakly fluorescent due to the photoinduced electron-transfer （PET） from the fluorophore to the receptor, and it displays evidently solvatochromic UV-vis and fluorescence spectra： the emission shifted from 495 nm in n-hexane to 545 nm in phosphate buffer solution. Michael addition reaction between thiols and the maleimide in MNP inhibited the PET process, which led to about eight-fold fluorescence enhancement. In addition, MNP showed highly sensitivity to rnercapto-containing proteins and it could detect as low as 20.4 μg/mL of BSA in PBS. MNP has potential in fluorescent imaging of thiols in living cells.

Effect of the exposure to suspended solids on the enzymatic activity in the bivalve Sinonovacula constricta

Aquatic animals are susceptible to sudden changes of their living environment but they adopt strategies to cope with adverse environmental challenges.Contamination by suspended solids,often associated with a dramatic change in the concentrations of important water-quality variables is a frequent occurrence in China's coastal waters and estuaries.Here we studied the impact of suspended solids on the activities of the antioxidant enzymes superoxide dismutase(SOD)and catalase(CAT),as well as adenosine triphosphates(including Na^(+)K^(+)-ATPase,Mg^(++)-ATPase,Ca^(++)-ATPase)and H^(+)K^(+)-ATPase in the gills and visceral mass tissues of the molluscan bivalve Sinonovacula constricta exposed(4,8,12,16,20,and 24 days)to various concentrations of suspended solids.Our results showed that the antioxidant enzymes cooperated closely to effectively scavenge superoxide anion free radicals and H2O2(which can ultimately inhibit gill activity)through the modification of SOD and/or CAT enzymatic activities.ATPases activity(considered to be a sensitive indicator of toxicity)could play an effective role in the maintenance of functional integrity of the plasma membranes as well as some other intracellular functions.After the exposure,a decrease in the Nat K^(+)-ATPase,Mg^(++)-ATPase,and Ca^(++)-ATPase activity of the gills was observed suggesting that they were inhibited by the treatments.These results also indicated that,from day 4 to day 16,exposure to high concentrations of suspended solids had an inhibitory effect on the activity of H^(+)-K^(+)-ATPase in the visceral mass of S.constricta.However,after a period of adaptation the H^(+)-K^(+)-ATPase activity was restored to original levels.Our results suggest that long-term exposure to high levels of suspended solids disturb osmoregulation,gastric acid secretion and digestion,cause oxidative damage,as a consequence of antioxidant enzymes inactivation which eventually damages the gills,affect the food intake and transformation,ultimately resulting in systems failure and eventually death.

Spatiotemporal distribution of size-fractioned phytoplankton in the Yalu River Estuary,China

The grain size structure of phytoplankton has great influence on shellfish culture.The present study aimed to assess the spatial and temporal variation in the phytoplankton community structure in the Yalu River Estuary and to explore the relationship between the phytoplankton community structure and various environmental parameters in 2020.High-throughput sequencing was used in this study.The results showed that nanophytoplankton,especially Karlodinium veneficum,dominated the estuary throughout the year.The biomass ratio of picophytoplankton,nanophytoplankton,and microphytoplankton were 20:63:17 in spring,30:44:26 in summer,1:38:61 in autumn,and 2:45:53 in winter,respectively.Meanwhile,Dinophyta had the greatest biomass throughout the year,followed by Bacillariophyta.On the spatial dimension(Station average),COD,T,SST had a positive impact on total phytoplankton communities,and Dep had a negative impact.In the time dimension(Monthly average),the environmental factor that significantly controlled the phytoplankton community structure were NO2 and SST.

Discrimination of biothiols in different media with NBD-F as the probe

4-Fluoro-7-nitrobenzo-2-oxa-1,3-diazole（NBD-F） was employed as a colorimetric probe for differential detection of biothiols in different media. The spectral response and the selectivity of NBD-F toward thiols were significantly improved by surfactant micelles. Mercapto group exhibited high reactivity in all the solvents（including Tris–HCl buffer solution, CTAB and SDS micelles）. The 4-thioether derivatives of NBDF reacting with Cys and Hcy but not GSH could transfer to the corresponding 4-amino-substituents via intramolecular nucleophilic aromatic substitution, thus, GSH could be discriminated from Cys/Hcy. In CTAB micelles, the reaction product of NBD-F with Cys is non-fluorescent and it absorbs in longwavelength region. According to the spectral responses of NBD-F toward different low-molecularweight thiols, we could identify Cys, Hcy and GSH from each other.