Microbiome Engineering:A Promising Approach to Improve Coral Health

The world’s coral reefs are threatened by the cumulative impacts of global climate change and local stressors.Driven largely by a desire to understand the interactions between corals and their symbiotic microorganisms,and to use this knowledge to eventually improve coral health,interest in coral microbiology and the coral microbiome has increased in recent years.In this review,we summarize the role of the coral microbiome in maintaining a healthy metaorganism by providing nutrients,support for growth and development,protection against pathogens,and mitigation of environmental stressors.We explore the concept of coral microbiome engineering,that is,precise and controlled manipulation of the coral microbiome to aid and enhance coral resilience and tolerance in the changing oceans.Although coral microbiome engineering is clearly in its infancy,several recent breakthroughs indicate that such engineering is an effective tool for restoration and preservation of these valuable ecosystems.To assist with identifying future research targets,we have reviewed the common principles of microbiome engineering and its applications in improving human health and agricultural productivity,drawing parallels to where coral microbiome engineering can advance in the not-too-distant future.Finally,we end by discussing the challenges faced by researchers and practitioners in the application of microbiome engineering in coral reefs and provide recommendations for future work.

Increased light availability enhances tolerance against ocean acidification-related stress in the calcifying macroalga Halimedaopuntia

Although the adverse impacts of ocean acidification(OA)on marine calcifiers have been investigated extensively,the anti-stress capabilities regulated by increased light availability are unclear.Herein,the interactive effects of three light levels(30μmol photons/(m^(2)·s),150μmol photons/(m^(2)·s),and 240μmol photons/(m^(2)·s)combined with two pCO_(2)concentrations(400 ppmv and 1400 ppmv)on the physiological acclimation of the calcifying macroalga Halimeda opuntia were investigated using a pCO_(2)-light coupling experiment.The OA negatively influenced algal growth,calcification,photosynthesis,and other physiological performances in H.opuntia.The relative growth rate under elevated pCO_(2)conditions significantly declined by 13.14%−41.29%,whereas net calcification rates decreased by nearly three-fold under OA conditions.Notably,increased light availability enhanced stress resistance through the accumulation of soluble organic molecules,especially soluble carbohydrate,soluble protein,and free amino acids,and in combination with metabolic enzyme-driven activities,OA stress was alleviated.The carotenoid content under low light conditions increased markedly,and the rapid light curve of the relative electron transport rate was enhanced significantly by increasing light intensities,indicating that this new organization of the photosynthetic machinery in H.opuntia accommodated light variations and elevated pCO_(2)conditions.Thus,the enhanced metabolic performance of the calcifying macroalga H.opuntia mitigated OA-related stress.

Molecular quantification of copepod Acartia erythraea feeding on different algae preys

Quantitative evaluation of the copepod feeding process is critical for understanding the functioning of marine food webs, as this provides a major link between primary producers and higher trophic levels. In this study, a molecular protocol based on quantitative polymerase chain reaction(qPCR) targeting 18S rDNA was developed and used to investigate the feeding and digestion rates of the copepod Acartia erythraea in a laboratory experiment using microalgae Thalassiosira weissflogii, Prorocentrum shikokuense, and Alexandrium catenella as prey. Although offered an equal encounter rate based on biovolume, prey uptake varied substantially among the three algal species, with the ingestion rate(IR) and digestion rate(DR) of A. erythraea differing significantly(P <0.001) based on both cell counting and qPCR detection. Acartia erythraea showed the highest IR(2.79×10~4 cells/(ind.·h)) and DR(2.43×10~4 cells/(ind.·h)) on T. weissflogii, and the lowest amounts of ingested P. shikokuense were detected. The highest assimilation rate(~90.64%, IR/DR) was observed in copepods fed with P. shikokuense. The qPCR method used here can help determine the digestion rate and assimilation rate of copepods by detecting cells remaining in the gut hence providing the possibility to examine trophic links involving key species in the marine ecosystem. Our results indicate that A. erythraea has diet-specific feeding performance in different processes, and a quantitative assessment of copepod feeding is needed to accurately determine its functional role in the energy and matter uptake from marine food webs.

Characterization of the P450 Monooxygenase LobP1 as C-32 Hydroxylase in Lobophorin Biosynthesis

Lobophorins(LOBs)belong to a large family of spirotetronate antibiotics with antibacterial and antitumor activities.In this study,we demonstrated the function of LobP1,a P450 monooxygenase encoded in the LOB biosynthetic gene cluster,by in vivo deletion and in vitro biochemical assays.The disruption of lobP1 led to the isolation of three new LOBs derivatives(3-5)and three known ones(6-8)without the hydroxyl group at C-32.LobP1 was shown to have relatively broad substrate scope.Determining the kinetic parameters of LobP1 towards different substrates revealed that LobP1 preferred substrate with a nitrosugar.The new LOBs 3-5 displayed significant antibacterial activities against Bacillus subtilis and Micrococcus luteus with MIC values of 0.125 to 1μg·mL^(-1),and the major product LOB E(6)from the∆lobP1 mutant showed moderate cytotoxic activities against several cancer cell lines.

Environmentally friendly expanded graphite-doped ZnO superhydrophobic coating with good corrosion resistance in marine environment

Designing and fabricating the marine anti-corrosion materials without fluorine by superhydrophobic method is a huge challenge. In this study, an environmentally friendly composite coating was prepared by combing modified expanded graphite(EAG) with nano zinc oxide(ZnO). This coating showed superhydrophobic surface and good corrosion resistance. Fourier transform infrared spectroscopy(FITR), X-ray diffraction(XRD),and scanning electron microscopy(SEM) were used to characterize the materials in fabricating process of the coating. The properties of three composite coatings(ZnO,EAG, and EAG@ZnO) were analyzed, including surface roughness, water contact angle, corrosion resistance, selfcleaning and anti-fouling. The combination of ZnO and EAG caused a big water contact angle, leading superhydrophobic surface of the composite coatings. The electrochemical results showed that the superhydrophobic EAG@ZnO coating had a larger capacitive arc diameter and charge transfer resistance, indicating the enhanced anti-corrosion resistance. Meanwhile, the EAG@ZnO coating also showed good self-cleaning and anti-fouling performance according to solid and liquid pollutants tests.In addition, the mechanical properties and stability of the superhydrophobic EAG@ZnO coatings were evaluated by knife peeling and finger scratch tests. In summary, these superhydrophobic and anti-fouling EAG@ZnO composite coatings provide a potential application in marine corrosion and protection field.

Green synthesis of functional metallic nanoparticles by dissimilatory metal-reducing bacteria“Shewanella”:A comprehensive review

The biosynthesis strategy of nanoparticles has attracted much attention due to the mild synthesis condi-tions,environmental-friendly properties,and low costs.Biosynthesized nanoparticles(bio-NPs)not only show excellent physicochemical properties,but also exhibit high stability,enlarged specific surface area,and excellent biocompatibility,which are crucial for industrial,agricultural,and medical fields.She-wanella,a kind of dissimilatory metal-reducing bacteria,is regarded as a typical biosynthesis-functional bacteria class with wide distribution and strong adaptability.Thus,in this paper,functional bio-NPs by Shewanella were reviewed to provide a comprehensive view of current research progress.The biosynthetic mechanisms of Shewanella are summarized as the Mtr pathway(predominant),extracellular polymeric substance-induced pathway,and enzyme/protein-induced pathway.During the biosynthesis process,bio-logical factors along with the physicochemical parameters highly influenced the properties of the resul-tant bio-NPs.Till now,bio-NPs have been applied in various fields including environmental remediation,antibacterial applications,and microbial fuel cells.However,some challenging issues of bio-NPs by She-wanella remain unsolved,such as optimizing suitable bacterial strains,intelligently controlling bio-NPs,clarifying biosynthesis mechanisms,and expanding bio-NPs applications.

Organophosphate Esters in Air and Seawater of the South China Sea:Spatial Distribution,Transport,and Air−Sea Exchange

Organophosphate esters(OPEs)have become one group of chemicals with emerging concern in the marine environment.In this work,we investigated OPEs in the air and seawater of the South China Sea in summer 2019.The concentrations of∑_(10)OPEs in the atmosphere ranged from 66 to 550 pg/m^(3),with TCIPP,TNBP,TPhP,and TEP predominating in the air.The total dissolved OPE concentrations(∑_(10)OPEs without TEP)measured in high-volume water samples ranged from 300 to 3600 pg/L,with a mean concentration of 1180±910 pg/L.TEP was measured with liquid−liquid extraction(LLE),and it showed the highest concentration(average 2000±1450 pg/L)among the selected OPEs.Total suspended matter associated OPEs accounted for less than 4.7%of the sum of OPE concentrations in seawater.Fugacity fractions and air−sea exchange fluxes showed that TCEP,TCIPP,TIBP,TEHP,TPhP,and EHDPP were favored to volatilize,TEP dominated the deposition,while TPrP and TNBP varied between volatilization and deposition.Atmospheric particle deposition fluxes ranged from 5 to 71 ng/m^(2)/day with an average of 17±15 ng/m^(2)/day.The input of∑OPEs to the entire South China Sea via atmospheric particle deposition was estimated to be 22±19 tons/year,while the net air−sea exchange fluxes of OPEs were volatilization from seawater to air with an average of 44±33 tons/year.This work suggests that air−sea exchange and atmospheric particle deposition are significant processes interfering with the transport of OPEs in the marine environment.