Global development has been heavily reliant on the overexploitation of natural resources since the Industrial Revolution. With the extensive use of fossil fuels, deforestation, and other forms of ...land-use change, anthropogenic activities have contributed to the ever-increasing concentrations of greenhouse gases (GHGs) in the atmosphere, causing global climate change. In response to the worsening global climate change, achieving carbon neutrality by 2050 is the most pressing task on the planet. To this end, it is of utmost importance and a significant challenge to reform the current production systems to reduce GHG emissions and promote the capture of CO2 from the atmosphere. Herein, we review innovative technologies that offer solutions achieving carbon (C) neutrality and sustainable development, including those for renewable energy production, food system transformation, waste valorization, C sink conservation, and C-negative manufacturing. The wealth of knowledge disseminated in this review could inspire the global community and drive the further development of innovative technologies to mitigate climate change and sustainably support human activities.
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•Carbon neutrality may be achieved by reforming current global development systems to minimize greenhouse gas emissions and increase CO2 capture•Harnessing the power of renewable and carbon-neutral resources to produce energy and other fossil-based alternatives may eliminate our dependence on fossil fuels•Protecting natural carbon sinks and promoting CO2 capture, utilization, and storage are conducive to mitigating climate change•This review presents the current state, opportunities, challenges, and perspectives of technologies related to achieving carbon neutrality
Indicators related to organic matter are important when assessing aquatic environment quality. The chemical oxygen demand (COD) is widely used as a water quality reference. However, oxidizing agents ...used to determine the COD can oxidize refractory organic matter that is not pollutant and can persist in the ocean for thousands of years. This means the COD can misrepresent the water quality. The actual water quality can be indicated better by the biochemical oxygen demand (BOD) than the COD, but determining the BOD is time-consuming and gives variable results. In this study, the optical properties of dissolved organic matter in water samples from the Chinese coast that had been incubated for a long time or directly oxidized using COD oxidant were analyzed. The results indicated that the oxidizing agent rapidly oxidized 22.93% ± 4.96% of refractory dissolved organic matter (RDOM) that was resistant to microbial degradation, implying that RDOM made a marked contribution to the COD. Meanwhile, size-fractional fluorescence spectroscopy and COD measurements indicated that the COD of the >0.7 μm fraction and the fluorescence intensity of the protein-like component significantly positively correlated with the BOD of the bulk sample. This indicated that, for monitoring organic pollutants in coastal waters, the COD of the >0.7 μm fraction could be used as a proxy for the standard COD and that the fluorescence intensity of the protein-like component could be used as a convenient proxy for the BOD. The method can help retain recalcitrant organic matter in seawater to act as a carbon sink.
•DOM was distinctly different after biodegradation versus chemical oxidation.•Refractory DOC contributed a considerable portion of the COD.•The COD of the >0.7 μm fraction most strongly correlated with the BOD5.•The COD of the >0.7 μm fraction can be used instead of the bulk COD indicator.•The protein-like fluorescence intensity can be used as a fast/stable proxy for BOD5.
The biological pump is a process whereby CO(2) in the upper ocean is fixed by primary producers and transported to the deep ocean as sinking biogenic particles or as dissolved organic matter. The ...fate of most of this exported material is remineralization to CO(2), which accumulates in deep waters until it is eventually ventilated again at the sea surface. However, a proportion of the fixed carbon is not mineralized but is instead stored for millennia as recalcitrant dissolved organic matter. The processes and mechanisms involved in the generation of this large carbon reservoir are poorly understood. Here, we propose the microbial carbon pump as a conceptual framework to address this important, multifaceted biogeochemical problem.
Schematic of the coastal microorganism-mediated dissolved organic matter transformation.
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•Bacteria transformed the DOM from a relatively high to a low molecular weight.•Microbial ...transformation render “dark” organic matter visible in mass spectrometry.•K- and r-strategists showed different correlations with two-size categories of DOM.•DOM chemodiversity and microbial biodiversity exhibited tight connections.•DOM variations are more crucial in shaping microbial communities than vice versa.
Dissolved organic matter (DOM) changes in quantity and quality over time and space, especially in highly dynamic coastal estuaries. Bacterioplankton usually display seasonal and spatial variations in abundance and composition in the coastal regions, and influence the DOM pool via assimilation, transformation and release of organic molecules. The change in DOM can also affect the composition of bacterial community. However, little is known on the correspondence between DOM molecules and bacterial composition, particularly through a systematic field survey. In this study, the spatiotemporal signatures of microbial communities and DOM composition in the subtropical coastal estuary of Xiamen are investigated over one and half years. The co-occurrence analysis between bacteria and DOM suggested microorganisms likely transformed the DOM from a relatively high (>400 Da) to a low (<400 Da) molecular weight, corresponding to an apparent increase in overall aromaticity. This might be the reason why microbial transformation renders “dark” organic matter visible in mass spectrometry due to more efficient ionization of microbial metabolites, as well as photodegradation processes. K- and r-strategists exhibited different correlations with two-size categories of DOM molecules owing to their different lifestyles and responses to environmental nutrient conditions. A comparison of the environmental variables and DOM composition with the microbial communities showed that the environmental/DOM variations played a more important role in shaping the microbial communities than vice versa. This study sheds light on the interactions between microbial populations and DOM molecules at the spatiotemporal scale, improving our understanding of microbial roles in marine biogeochemical cycles.
Most marine bacteria can produce exopolysaccharides (EPS). However, very few structures of EPS produced by marine bacteria have been determined. The characterization of EPS structure is important for ...the elucidation of their biological functions and ecological roles. In this study, the structure of EPS produced by a marine bacterium,
sp. JL2810, was characterized, and the biosorption of the EPS for heavy metals Cu
, Ni
, and Cr
was also investigated. Nuclear magnetic resonance (NMR) analysis indicated that the JL2810 EPS have a novel structure consisting of the repeating unit of -3)-α-Rha
-(1→3)-α-Man
-(1→4)-α-3OAc-GalA
-(1→. The biosorption of the EPS for heavy metals was affected by a medium pH; the maximum biosorption capacities for Cu
and Ni
were 140.8 ± 8.2 mg/g and 226.3 ± 3.3 mg/g at pH 5.0; however, for Cr
it was 215.2 ± 5.1 mg/g at pH 5.5. Infrared spectrometry analysis demonstrated that the groups of O-H, C=O, and C-O-C were the main function groups for the adsorption of JL2810 EPS with the heavy metals. The adsorption equilibrium of JL2810 EPS for Ni
was further analyzed, and the equilibrium data could be better represented by the Langmuir isotherm model. The novel EPS could be potentially used in industrial applications as a novel bio-resource for the removal of heavy metals.
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•Molecular composition of water-extractable DOM was analyzed in two deep-sea sediment cores.•Microbial community composition was linked to DOM composition in the sediment ...cores.•Microbes play a crucial role in the distribution of sedimentary recalcitrant DOM.•Sediments are a potential source of deep-sea recalcitrant DOM.
Sedimentary organic matter provides carbon substrates and energy sources for microorganisms, which drive benthic biogeochemical processes and in turn modify the quantity and quality of dissolved organic matter (DOM). However, the molecular composition and distribution of DOM and its interactions with microbes in deep-sea sediments remain poorly understood. Here, molecular composition of DOM and its relationship with microbes were analyzed in samples collected from two sediment cores (∼40 cm below the sea floor), at depths of 1157 and 2253 m from the South China Sea. Results show that niche differentiation was observed on a fine scale in different sediment layers, with Proteobacteria and Nitrososphaeria dominating the shallow sediments (0–6 cm) and Chloroflexi and Bathyarchaeia prevailing in deeper sediments (6–40 cm), indicating correspondence of microbial community composition with both geographical isolation and the availability of organic matter. An intimate link between the DOM composition and microbial community further indicates that, microbial mineralization of fresh organic matter in the shallow layer potentially resulted in the accumulation of recalcitrant DOM (RDOM), while relatively low abundance of RDOM was linked to anaerobic microbial utilization in deeper sediment layers. In addition, higher RDOM abundance in the overlying water, as compared to that in the surface sediment, suggests that sediment might be a source of deep-sea RDOM. These results emphasize the close relation between the distribution of sediment DOM and different microbial community, laying a foundation for understanding the complex dynamics of RDOM in deep-sea sediment and water column.
Summary
Investigating the interactions between marine cyanobacteria and their viruses (phages) is important towards understanding the dynamic of ocean's primary productivity. Genome sequencing of ...marine cyanophages has greatly advanced our understanding about their ecology and evolution. Among 24 reported genomes of cyanophages that infect marine picocyanobacteria, 17 are from cyanomyoviruses and six from cyanopodoviruses, and only one from cyanosiphovirus (Prochlorococcus phage P‐SS2). Here we present four complete genome sequences of siphoviruses (S‐CBS1, S‐CBS2, S‐CBS3 and S‐CBS4) that infect four different marine Synechococcus strains. Three distinct subtypes were recognized among the five known marine siphoviruses (including P‐SS2) in terms of morphology, genome architecture, gene content and sequence similarity. Our study revealed that cyanosiphoviruses are genetically diverse with polyphyletic origin. No core genes were found across these five cyanosiphovirus genomes, and this is in contrast to the fact that many core genes have been found in cyanomyovirus or cyanopodovirus genomes. Interestingly, genes encoding three structural proteins and a lysozyme of S‐CBS1 and S‐CBS3 showed homology to a prophage‐like genetic element in two freshwater Synechococcus elongatus genomes. Re‐annotation of the prophage‐like genomic region suggests that S. elongatus may contain an intact prophage. Cyanosiphovirus genes involved in DNA metabolism and replication share high sequence homology with those in cyanobacteria, and further phylogenetic analysis based on these genes suggests that ancient and selective genetic exchanges occurred, possibly due to past prophage integration. Metagenomic analysis based on the Global Ocean Sampling database showed that cyanosiphoviruses are present in relatively low abundance in the ocean surface water compared to cyanomyoviruses and cyanopodoviruses.
Microorganisms drive much of the marine nitrogen (N) cycle, which jointly controls the primary production in the global ocean. However, our understanding of the microbial communities driving the ...global ocean N cycle remains fragmented. Focusing on "who is doing what, where, and how?", this study draws a clear picture describing the global biogeography of marine N-cycling microbial communities by utilizing the
Oceans shotgun metagenomes. The marine N-cycling communities are highly variable taxonomically but relatively even at the functional trait level, showing clear functional redundancy properties. The functional traits and taxonomic groups are shaped by the same set of geo-environmental factors, among which, depth is the major factor impacting marine N-cycling communities, differentiating mesopelagic from epipelagic communities. Latitudinal diversity gradients and distance-decay relationships are observed for taxonomic groups, but rarely or weakly for functional traits. The composition of functional traits is strongly deterministic as revealed by null model analysis, while a higher degree of stochasticity is observed for taxonomic composition. Integrating multiple lines of evidence, in addition to drawing a biogeographic picture of marine N-cycling communities, this study also demonstrated an essential microbial ecological theory-determinism governs the assembly of microbial communities performing essential biogeochemical processes; the environment selects functional traits rather than taxonomic groups; functional redundancy underlies stochastic taxonomic community assembly.
A critical question in microbial ecology is how the complex microbial communities are formed in natural ecosystems with the existence of thousands different species, thereby performing essential ecosystem functions and maintaining ecosystem stability. Previous studies disentangling the community assembly mechanisms mainly focus on microbial taxa, ignoring the functional traits they carry. By anchoring microbial functional traits and their carrying taxonomic groups involved in nitrogen cycling processes, this study demonstrated an important mechanism associated with the complex microbial community assembly. Evidence shows that the environment selects functional traits rather than taxonomic groups, and functional redundancy underlies stochastic taxonomic community assembly. This study is expected to provide valuable mechanistic insights into the complex microbial community assembly in both natural and artificial ecosystems.
Bacteria play critical roles in marine nutrient cycles by incorporating and redistributing dissolved organic matter (DOM) and inorganic nutrients in the ocean. TonB-dependent transporter (TBDT) ...proteins allow Gram-negative bacteria to take up scarce resources from nutrient-limiting environments as well as siderophores, heme, vitamin B12, and recently identified carbohydrates. Thus, the characterization of TBDT distribution and functions is essential to better understand the contribution TBDT to DOM assimilation and its consequences on nutrient cycling in the environment.
This study presents the distribution of encoded known and putative TBDT proteins in the genomes of microorganisms and from the Global Ocean Survey data. Using a Lek clustering algorithm and substrate specificities, the TBDT sequences were mainly classified into the following three groups: (1) DOM transporters; (2) Siderophores/Vitamins transporters; and (3) Heme/Hemophores/Iron(heme)-binding protein transporters. Diverse TBDTs were found in the genomes of oligotroph Citromicrobium bathyomarinum JL354 and Citromicrobium sp JLT1363 and were highly expressed in the stationary phase of bacterial growth. The results show that the Gammaproteobacteria and the Cytophaga-Flavobacterium-Bacteroides (CFB) group bacteria accounted for the majority of the TBDT gene pool in marine surface waters.
The results of this study confirm the ecological importance of TBDTs in DOM assimilation for bacteria in marine environments owing to a wide range of substrate utilization potential in the ubiquitous Gammaproteobacteria and CFB group bacteria.
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