Search

Hydrogen sulfide (H 2 S), methanethiol (MeSH) and dimethylsulfide (DMS) are abundant sulfur gases with roles in biogeochemical cycling, chemotaxis and/or climate regulation. Catabolism of the marine osmolyte dimethylsulfoniopropionate (DMSP) is a major source of DMS and MeSH, but both also result from S-methylation of H 2 S via MddA, an H 2 S and MeSH S-methyltransferase whose gene is abundant in soil but scarce in marine environments. Here we identify the S-adenosine methionine (SAM)-dependent MeSH and H 2 S S-methyltransferase 'MddH', which is widespread in diverse marine bacteria and some freshwater and soil bacteria. mddH is predicted in up to ~5% and ~15% of seawater and coastal sediment bacteria, respectively, which is considerably higher than mddA. Furthermore, marine mddH transcript levels are similar to those for the most abundant DMSP lyase gene dddP. This study implies that the importance of H 2 S and MeSH S-methylation pathways in marine environments is significantly underestimated., (© 2024. The Author(s).)

Coral reefs rely heavily on reef fish for their health, yet overfishing has resulted in their decline, leading to an increase in fast-growing algae and changes in reef ecosystems, a phenomenon described as the phase-shift. A clearer understanding of the intricate interplay between herbivorous, their food, and their gut microbiomes could enhance reef health. This study examines the gut microbiome and isotopic markers (δ 13 C and δ 15 N) of four key nominally herbivorous reef fish species (Acanthurus chirurgus, Kyphosus sp., Scarus trispinosus, and Sparisoma axillare) in the Southwestern Atlantic's Abrolhos Reef systems. Approximately 16.8 million 16S rRNA sequences were produced for the four fish species, with an average of 317,047 ± 57,007 per species. Bacteria such as Proteobacteria, Firmicutes, and Cyanobacteria were prevalent in their microbiomes. These fish show unique microbiomes that result from co-diversification, diet, and restricted movement. Coral-associated bacteria (Endozoicomonas, Rhizobia, and Ruegeria) were found in abundance in the gut contents of the parrotfish species Sc. trispinosus and Sp. axillare. These parrotfishes could aid coral health by disseminating such beneficial bacteria across the reef. Meanwhile, Kyphosus sp. predominantly had Pirellulaceae and Rhodobacteraceae. Four fish species had a diet composed of turf components (filamentous Cyanobacteria) and brown algae (Dictyopteris). They also had similar isotopic niches, suggesting they shared food sources. A significant difference was observed between the isotopic signature of fish muscular gut tissue and gut contents, pointing to the role that host genetics and gut microbes play in differentiating fish tissues., (© 2024. The Author(s).)

Dimethylsulfoniopropionate (DMSP) is one of the Earth's most abundant organosulfur compounds because many marine algae, bacteria, corals and some plants produce it to high mM intracellular concentrations. In these organisms, DMSP acts an anti-stress molecule with purported roles to protect against salinity, temperature, oxidative stress and hydrostatic pressure, amongst many other reported functions. However, DMSP is best known for being a major precursor of the climate-active gases and signalling molecules dimethylsulfide (DMS), methanethiol (MeSH) and, potentially, methane, through microbial DMSP catabolism. DMSP catabolism has been extensively studied and the microbes, pathways and enzymes involved have largely been elucidated through the application of molecular research over the last 17 years. In contrast, the molecular biology of DMSP synthesis is a much newer field, with the first DMSP synthesis enzymes only being identified in the last 5 years. In this review, we discuss how the elucidation of key DMSP synthesis enzymes has greatly expanded our knowledge of the diversity of DMSP-producing organisms, the pathways used, and what environmental factors regulate production, as well as to inform on the physiological roles of DMSP. Importantly, the identification of key DMSP synthesis enzymes in the major groups of DMSP producers has allowed scientists to study the distribution and predict the importance of different DMSP-producing organisms to global DMSP production in diverse marine and sediment environments. Finally, we highlight key challenges for future molecular research into DMSP synthesis that need addressing to better understand the cycling of this important marine organosulfur compound, and its magnitude in the environment., (Copyright © 2023. Published by Elsevier Inc.)

High hydrostatic pressure (HHP) is a characteristic environmental factor of the deep ocean. However, it remains unclear how piezotolerant bacteria adapt to HHP. Here, we identify a two-step metabolic pathway to cope with HHP stress in a piezotolerant bacterium. Myroides profundi D25 T , obtained from a deep-sea sediment, can take up trimethylamine (TMA) through a previously unidentified TMA transporter, TmaT, and oxidize intracellular TMA into trimethylamine N -oxide (TMAO) by a TMA monooxygenase, Mp Tmm. The produced TMAO is accumulated in the cell, functioning as a piezolyte, improving both growth and survival at HHP. The function of the TmaT- Mp Tmm pathway was further confirmed by introducing it into Escherichia coli and Bacillus subtilis Encoded TmaT-like and Mp Tmm-like sequences extensively exist in marine metagenomes, and other marine Bacteroidetes bacteria containing genes encoding TmaT-like and Mp Tmm-like proteins also have improved HHP tolerance in the presence of TMA, implying the universality of this HHP tolerance strategy in marine Bacteroidetes., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

Dimethylsulfoniopropionate (DMSP) is an important marine osmolyte. Aphotic environments are only recently being considered as potential contributors to global DMSP production. Here, our Mariana Trench study reveals a typical seawater DMSP/dimethylsulfide (DMS) profile, with highest concentrations in the euphotic zone and decreased but consistent levels below. The genetic potential for bacterial DMSP synthesis via the dsyB gene and its transcription is greater in the deep ocean, and is highest in the sediment.s DMSP catabolic potential is present throughout the trench waters, but is less prominent below 8000 m, perhaps indicating a preference to store DMSP in the deep for stress protection. Deep ocean bacterial isolates show enhanced DMSP production under increased hydrostatic pressure. Furthermore, bacterial dsyB mutants are less tolerant of deep ocean pressures than wild-type strains. Thus, we propose a physiological function for DMSP in hydrostatic pressure protection, and that bacteria are key DMSP producers in deep seawater and sediment.

Microbial production and catabolism of dimethylsulfoniopropionate (DMSP), generating the climatically active gases dimethyl sulfide (DMS) and methanethiol (MeSH), have key roles in global carbon and sulfur cycling, chemotaxis, and atmospheric chemistry. Microorganisms in the sea surface microlayer (SML), the interface between seawater and atmosphere, likely play an important role in the generation of DMS and MeSH and their exchange to the atmosphere, but little is known about these SML microorganisms. Here, we investigated the differences between bacterial community structure and the distribution and transcription profiles of the key bacterial DMSP synthesis (dsyB and mmtN) and catabolic (dmdA and dddP) genes in East China Sea SML and subsurface seawater (SSW) samples. Per equivalent volume, bacteria were far more abundant (~ 7.5-fold) in SML than SSW, as were those genera predicted to produce DMSP. Indeed, dsyB (~ 7-fold) and mmtN (~ 4-fold), robust reporters for bacterial DMSP production, were also far more abundant in SML than SSW. In addition, the SML had higher dsyB transcripts (~ 3-fold) than SSW samples, which may contribute to the significantly higher DMSP level observed in SML compared with SSW. Furthermore, the abundance of bacteria with dmdA and their transcription were higher in SML than SSW samples. Bacteria with dddP and transcripts were also prominent, but less than dmdA and presented at similar levels in both layers. These data indicate that the SML might be an important hotspot for bacterial DMSP production as well as generating the climatically active gases DMS and MeSH, a portion of which are likely transferred to the atmosphere.

Tachyplesin I (TPI) is a cationic β-hairpin antimicrobial peptide with broad-spectrum, potent antimicrobial activity. In this study, the all d-amino acid analogue of TPI (TPAD) was synthesized, and its structure and activity were determined. TPAD has comparable antibacterial activity to TPI on 14 bacterial strains, including four drug-resistant bacteria. Importantly, TPAD has significantly improved stability against enzymatic degradation and decreased hemolytic activity compared to TPI, indicating that it has better therapeutic potential. The induction of bacterial resistance using low concentrations of TPAD resulted in the activation of the QseC/B two-component system. Deletion of this system resulted in at least five-fold improvement of TPAD activity, and the combined use of TPAD with LED209, a QseC/B inhibitor, significantly enhanced the bactericidal effect against three classes of multidrug-resistant bacteria.

Background: The Mariana Trench is the deepest known site in the Earth's oceans, reaching a depth of ~ 11,000 m at the Challenger Deep. Recent studies reveal that hadal waters harbor distinctive microbial planktonic communities. However, the genetic potential of microbial communities within the hadal zone is poorly understood., Results: Here, implementing both culture-dependent and culture-independent methods, we perform extensive analysis of microbial populations and their genetic potential at different depths in the Mariana Trench. Unexpectedly, we observed an abrupt increase in the abundance of hydrocarbon-degrading bacteria at depths > 10,400 m in the Challenger Deep. Indeed, the proportion of hydrocarbon-degrading bacteria at > 10,400 m is the highest observed in any natural environment on Earth. These bacteria were mainly Oleibacter, Thalassolituus, and Alcanivorax genera, all of which include species known to consume aliphatic hydrocarbons. This community shift towards hydrocarbon degraders was accompanied by increased abundance and transcription of genes involved in alkane degradation. Correspondingly, three Alcanivorax species that were isolated from 10,400 m water supplemented with hexadecane were able to efficiently degrade n-alkanes under conditions simulating the deep sea, as did a reference Oleibacter strain cultured at atmospheric pressure. Abundant n-alkanes were observed in sinking particles at 2000, 4000, and 6000 m (averaged 23.5 μg/gdw) and hadal surface sediments at depths of 10,908, 10,909, and 10,911 m (averaged 2.3 μg/gdw). The δ 2 H values of n-C 16/18 alkanes that dominated surface sediments at near 11,000-m depths ranged from - 79 to - 93‰, suggesting that these sedimentary alkanes may have been derived from an unknown heterotrophic source., Conclusions: These results reveal that hydrocarbon-degrading microorganisms are present in great abundance in the deepest seawater on Earth and shed a new light on potential biological processes in this extreme environment.

Ammonia-oxidizing archaea (AOA) and bacteria (AOB) vary in their contribution to nitrification in different environments. The eastern China marginal seas (ECMS) are featured by complex river runoffs and ocean currents, forming different sediment patches. Here, via quantitative PCR and clone library analysis of the amoA genes, we showed that AOB were more abundant than AOA in ECMS sediments. The abundance, diversity and richness of AOA, but not AOB, were higher in the East China Sea (ECS) than in the Yellow Sea (YS) and Bohai Sea (BS). Nitrosopumilus (AOA) and Nitrosospira (AOB) were predominant lineages, but their abundances varied significantly between ECS, and BS and YS. This was mainly attributed to salinity and dissolved oxygen of the bottom water. The discovery of a high abundance of Nitrosophaera at estuarine sites suggested strong terrigenous influence exerted on the AOA community. In contrast, variations in ocean conditions played more important roles in structuring the AOB community, which was separated by bottom water dissolved oxygen into two groups: the south YS, and the north YS and BS. This study provides a comprehensive insight into the spatial distribution pattern of ammonia-oxidizing prokaryotes in ECMS sediments, laying a foundation for understanding their relative roles in nitrification., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Although it has been more than a decade since the first discovery of AHL lactonase AiiA in Bacillus sp. 240B1, we are only beginning to understand the diversity of quorum quenching (QQ) enzymes. Most of the previously identified QQ enzymes are derived from nonmarine microorganisms. A novel marine-derived secretory AHL lactonase, MomL, was found in Muricauda olearia in our previous work and represents a novel type of AHL lactonase widespread in the ocean. Herein, we describe a culture-dependent method for the identification of microbial QQ enzymes, especially the high-throughput method for screening QQ bacteria from cultivable bacterial strains. This method should be capable of efficiently identifying QQ enzymes from various microbial origins. The discovery of more QQ enzymes will help us to understand their ecological roles and may provide potential as therapeutic agents.

Investigating the environmental influence on the community composition and abundance of denitrifiers in marine sediment ecosystem is essential for understanding of the ecosystem-level controls on the biogeochemical process of denitrification. In the present study, nirK-harboring denitrifying communities in different mud deposit zones of eastern China marginal seas (ECMS) were investigated via clone library analysis. The abundance of three functional genes affiliated with denitrification (narG, nirK, nosZ) was assessed by fluorescent quantitative PCR. The nirK-harboring microbiota were dominated by a few operational taxonomic units (OTUs), which were widely distributed in different sites with each site harboring their unique phylotypes. The mean abundance of nirK was significantly higher than that of narG and nosZ genes, and the abundance of narG was higher than that of nosZ. The inconsistent abundance profile of different functional genes along the process of denitrification might indicate that nitrite reduction occurred independently of denitrification in the mud deposit zones of ECMS, and sedimentary denitrification was accomplished by cooperation of different denitrifying species rather than a single species. Such important information would be missed when targeting only a single denitrifying functional gene. Analysis of correlation between abundance ratios and environmental factors revealed that the response of denitrifiers to environmental factors was not invariable in different mud deposit zones. Our results suggested that a comprehensive analysis of different denitrifying functional genes may gain more information about the dynamics of denitrifying microbiota in marine sediments.

The antibiotic resistance genes (ARGs) from urban waste may spread to the environment with the discharge of leachate. Fifteen types of ARGs, including tetracycline, sulfonamides, AmpC β-lactamase and the class 1 integron gene were detected in the samples from the largest leachate treatment plant (LTP) in Guangzhou and its effluent receiving bodies (soil and surface water). The results showed that ARGs in leachates were in high levels and varied with seasons. The abundance of ARGs in the influent from high to low was in the turn of summer, winter, spring. About 2 to 4 orders of magnitude of ARGs were eliminated by the whole leachate treatment process. The predominant ARGs in the receiving soil were intI1, tetB, sul2, tetA and tetX, while those in the receiving surface water were sul2, intI1 and sul1, and the concentrations of ARGs in the receiving bodies were higher than those in the other natural bodies by 1 to 2 orders of magnitude. In addition, the results of bivariate correlation analysis showed that the abundances of ARGs (tetC, tetW, sul1, sul2, intI1 and FOX) were in significant correlation with the concentrations of heavy metals (Cu, Zn, Ni and Cr) (p < 0.05). LTPs are more likely to be sources of ARGs than wastewater treatment plant (WWTP) and need to be focused on., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Microbial communities of the Chinese marginal seas have rarely been reported. Here, bacterial and archaeal community structures and abundance in the surface sediment of four sea areas including the Bohai Sea (BS), North Yellow Sea (NYS), South Yellow Sea (SYS), and the north East China Sea (NECS) were surveyed by 16S ribosomal RNA (rRNA) gene pyrosequencing and quantitative PCR. The results showed that microbial communities of the four geographic areas were distinct from each other at the operational taxonomic unit (OTU) level, whereas the microbial communities of the BS, NYS, and SYS were more similar to each other than to the NECS at higher taxonomic levels. Across all samples, Bacteria were numerically dominant relative to Archaea, and among them, Gammaproteobacteria and Euryarchaeota were predominant in the BS, NYS, and SYS, while Deltaproteobacteria and Thaumarchaeota were prevalent in the NECS. The most abundant bacterial genera were putative sulfur oxidizer and sulfate reducer, suggesting that sulfur cycle processes might prevail in these areas, and the high abundance of dsrB (10(7)-10(8) copies g(-1)) in all sites verified the dominance of sulfate reducer in the north Chinese marginal seas. The differences in sediment sources among the sampling areas were potential explanations for the observed microbial community variations. Furthermore, temperature and dissolved oxygen of bottom water were significant environmental factors in determining both bacterial and archaeal communities, whereas chlorophyll a in sediment was significant only in structuring archaeal community. This study presented an outline of benthic microbial communities and provided insights into understanding the biogeochemical cycles in sediments of the north Chinese marginal seas.

In the present study, benthic microbial communities along the Pearl Estuary, a typical subtropical estuary in China subjected to extensive anthropogenic disturbance, were investigated using 16S rRNA gene-based pyrosequencing. The results showed that microbial communities in freshwater samples were clearly distinct from those in saltwater samples, since the relative sequence abundances of Deltaproteobacteria, Thermoplasmata and Marine Group I (MG-I) were higher in saltwater sediments, whereas Chloroflexi, Spirochaetes, Betaproteobacteria and methanogens were more prevalent in freshwater sediments. In addition, bacterial communities showed vertical stratifications in saltwater sediments, but remained constant with depth in freshwater sediments. The total organic carbon and carbon/nitrogen ratio in sediments correlated significantly with the overall community variations. The predominance of various microorganisms in specific niches led to efforts to identify their functional couplings by exploring their co-occurrence patterns. Using network analysis, strong positive correlations were observed between sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria, and between SRB and nitrite-oxidizing bacteria, indicating the potential interactions of intra-sulfur cycle processes, as well as sulfur and nitrogen cycles, in coastal sediments. Archaeal clades revealed strong and wide correlations between the Miscellaneous Crenarchaeotal Group (MCG) and other groups, suggesting a central role of MCG in the coastal benthic environment. Inversely, MG-I displayed negative correlations with other clades, which might indicate that the lifestyles of heterotrophic and autotrophic clades were mutually exclusive. This study presented a detailed outline of the biogeographic patterns of benthic microbial communities along the Pearl Estuary and provided new information regarding the potential interactions of various biogeochemical cycles in coastal sediments.

The continuing emergence of antibiotic-resistant pathogens is a concern to human health and highlights the urgent need for the development of alternative therapeutic strategies. Quorum sensing (QS) regulates virulence in many bacterial pathogens, and thus, is a promising target for antivirulence therapy which may inhibit virulence instead of cell growth and division. This means that there is little selective pressure for the evolution of resistance. Many natural quorum quenching (QQ) agents have been identified. Moreover, it has been shown that many microorganisms are capable of producing small molecular QS inhibitors and/or macromolecular QQ enzymes, which could be regarded as a strategy for bacteria to gain benefits in competitive environments. More than 30 species of marine QQ bacteria have been identified thus far, but only a few of them have been intensively studied. Recent studies indicate that an enormous number of QQ microorganisms are undiscovered in the highly diverse marine environments, and these marine microorganism-derived QQ agents may be valuable resources for antivirulence therapy.

Quorum sensing (QS) is a population-dependent mechanism for bacteria to synchronize social behaviors such as secretion of virulence factors. The enzymatic interruption of QS, termed quorum quenching (QQ), has been suggested as a promising alternative anti-virulence approach. In order to efficiently identify QQ bacteria, we developed a simple, sensitive and high-throughput method based on the biosensor Agrobacterium tumefaciens A136. This method effectively eliminates false positives caused by inhibition of growth of biosensor A136 and alkaline hydrolysis of N-acylhomoserine lactones (AHLs), through normalization of β-galactosidase activities and addition of PIPES buffer, respectively. Our novel approach was successfully applied in identifying QQ bacteria among 366 strains and 25 QQ strains belonging to 14 species were obtained. Further experiments revealed that the QQ strains differed widely in terms of the type of QQ enzyme, substrate specificity and heat resistance. The QQ bacteria identified could possibly be used to control disease in aquaculture.

Surface seawater in the South Pacific Gyre (SPG) is one of the cleanest oceanic environments on earth, and the photosynthetic primary production is extremely low. Despite the ecological significance of the largest aquatic desert on our planet, microbial community composition in the ultra-oligotrophic seawater remain largely unknown. In this study, we collected surface seawater along a southern transect of the SPG during the Integrated Ocean Drilling Program (IODP) Expedition 329. Samples from four distinct sites (Sites U1368, U1369, U1370 and U1371) were examined, representing ~5400 kilometers of transect line from the gyre heart to the edge area. Real-time PCR analysis showed 16S rRNA gene abundance in the gyre seawater, ranging from 5.96×10(5) to 2.55×10(6) copies ml(-1) for Bacteria and 1.17×10(3) to 1.90×10(4) copies ml(-1) for Archaea. The results obtained by statistic analyses of 16S rRNA gene clone libraries revealed the community composition in the southern SPG area: diversity richness estimators in the gyre center (Sites U1368 & U1369) are generally lower than those at sites in the gyre edge (Sites U1370 & U1371) and their community structures are clearly distinguishable. Phylogenetic analysis showed the predominance of Proteobacteria (especially Alphaproteobacteria) and Cyanobacteria in bacterial 16S rRNA gene clone libraries, whereas phylotypes of Betaproteobacteria were only detected in the central gyre. Archaeal 16S rRNA genes in the clone libraries were predominated by the sequences of Marine Group II within the Euryarchaeota, and the Crenarchaeota sequences were rarely detected, which is consistent with the real-time PCR data (only 9.9 to 22.1 copies ml(-1)). We also performed cultivation of heterotrophic microbes onboard, resulting in 18.9% of phylogenetically distinct bacterial isolates at least at the species level. Our results suggest that the distribution and diversity of microbial communities in the SPG surface seawater are closely related to the ultra-oligotrophic oceanographic features in the Pacific Ocean.

Dimethylsulfoniopropionate (DMSP) is one of Earth's most abundant organosulfur molecules, and bacteria in marine sediments have been considered significant producers. However, the vertical profiles of DMSP content and DMSP-producing bacteria in subseafloor sediment have not been described. Here, we used culture-dependent and -independent methods to investigate microbial DMSP production and cycling potential in South China Sea (SCS) sediment. The DMSP content of SCS sediment decreased from 11.25 to 20.90 nmol g–1 in the surface to 0.56–2.08 nmol g–1 in the bottom layers of 8-m-deep subseafloor sediment cores (n = 10). Very few eukaryotic plastid sequences were detected in the sediment, supporting bacteria and not algae as important sediment DMSP producers. Known bacterial DMSP biosynthesis genes (dsyB and mmtN) were only predicted to be in 0.0007–0.0195% of sediment bacteria, but novel DMSP-producing isolates with potentially unknown DMSP synthesis genes and/or pathways were identified in these sediments, including Marinobacter (Gammaproteobacteria) and Erythrobacter (Alphaproteobacteria) sp. The abundance of bacteria with the potential to produce DMSP decreased with sediment depth and was extremely low at 690 cm. Furthermore, distinct DMSP-producing bacterial groups existed in surface and subseafloor sediment samples, and their abundance increased when samples were incubated under conditions known to enrich for DMSP-producing bacteria. Bacterial DMSP catabolic genes were also most abundant in the surface oxic sediments with high DMSP concentrations. This study extends the current knowledge of bacterial DMSP biosynthesis in marine sediments and implies that DMSP biosynthesis is not only confined to the surface oxic sediment zones. It highlights the importance of future work to uncover the DMSP biosynthesis genes/pathways in novel DMSP-producing bacteria. [ABSTRACT FROM AUTHOR]

The deep-sea water of the South Pacific Gyre (SPG, 20°S-45°S) is a cold and ultra-oligotrophic environment that is the source of cold-adapted enzymes. However, the characteristic features of psychrophilic enzymes derived from culturable microbes in the SPG remained largely unknown. In this study, the degradation properties of 174 cultures from the deep water of the SPG were used to determine the diversity of cold-adapted enzymes. Thus, the abilities to degrade polysaccharides, proteins, lipids, and DNA at 4, 16, and 28 °C were investigated. Most of the isolates showed one or more extracellular enzyme activities, including amylase, chitinase, cellulase, lipase, lecithinase, caseinase, gelatinase, and DNase at 4, 16, and 28 °C. Moreover, nearly 85.6 % of the isolates produced cold-adapted enzymes at 4 °C. The psychrophilic enzyme-producing isolates distributed primarily in Alteromonas and Pseudoalteromonas genera of the Gammaproteobacteria. Pseudoalteromonas degraded 9 types of macromolecules but not cellulose, Alteromonas secreted 8 enzymes except for cellulase and chitinase. Interestingly, the enzymatic activities of Gammaproteobacteria isolates at 4 °C were higher than those observed at 16 or 28 °C. In addition, we cloned and expressed a gene encoding an α-amylase (Amy2235) from Luteimonas abyssi XH031, and examined the properties of the recombinant protein. These cold-active enzymes may have huge potential for academic research and industrial applications. In addition, the capacity of the isolates to degrade various types of organic matter may indicate their unique ecological roles in the elemental biogeochemical cycling of the deep biosphere. [ABSTRACT FROM AUTHOR]

Dimethylsulfoniopropionate (DMSP) is one of Earth's most abundant organosulfur molecules. Recently, many marine heterotrophic bacteria were shown to produce DMSP, but few studies have combined culture-dependent and independent techniques to study their abundance, distribution, diversity and activity in seawater or sediment environments. Here we investigate bacterial DMSP production potential in East China Sea (ECS) samples. Total DMSP (DMSPt) concentration in ECS seawater was highest in surface waters (SW) where phytoplankton were most abundant, and it decreased with depth to near bottom waters. However, the percentage of DMSPt mainly apportioned to bacteria increased from the surface to the near bottom water. The highest DMSP concentration was detected in ECS oxic surface sediment (OSS) where phytoplankton were not abundant. Bacteria with the genetic potential to produce DMSP and relevant biosynthesis gene transcripts were prominent in all ECS seawater and sediment samples. Their abundance also increased with depth and was highest in the OSS samples. Microbial enrichments for DMSP-producing bacteria from sediment and seawater identified many novel taxonomic groups of DMSP-producing bacteria. Different profiles of DMSP-producing bacteria existed between seawater and sediment samples and there are still novel DMSP-producing bacterial groups to be discovered in these environments. This study shows that heterotrophic bacteria significantly contribute to the marine DMSP pool and that their contribution increases with water depth and is highest in seabed surface sediment where DMSP catabolic potential is lowest. Furthermore, distinct bacterial groups likely produce DMSP in seawater and sediment samples, and many novel producing taxa exist, especially in the sediment. [ABSTRACT FROM AUTHOR]