Long-term fertilization and tillage regimes have limited effects on structuring bacterial and denitrifier communities in a sandy loam UK soil.

Denitrification causes loss of available nitrogen from soil systems, thereby reducing crop productivity and increasing reliance on agrochemicals. The dynamics of denitrification and denitrifying communities are thought to be altered by land management practices, which affect the physicochemical properties of the soil. In this study, we look at the effects of long-term tillage and fertilization regimes on arable soils following 16 years of treatment in a factorial field trial. By studying the bacterial community composition based on 16S rRNA amplicons, absolute bacterial abundance and diversity of denitrification functional genes (nirK, nirS and nosZ), under conditions of minimum/conventional tillage and organic/synthetic mineral fertilizer, we tested how specific land management histories affect the diversity and distribution of both bacteria and denitrification genes. Bacterial and denitrifier communities were largely unaffected by land management history and clustered predominantly by spatial location, indicating that the variability in bacterial community composition in these arable soils is governed by innate environmental differences and Euclidean distance rather than agricultural management intervention.

Partitioning of soil phosphorus among arbuscular and ectomycorrhizal trees in tropical and subtropical forests.

Partitioning of soil phosphorus (P) pools has been proposed as a key mechanism maintaining plant diversity, but experimental support is lacking. Here, we provided different chemical forms of P to 15 tree species with contrasting root symbiotic relationships to investigate plant P acquisition in both tropical and subtropical forests. Both ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) trees responded positively to addition of inorganic P, but strikingly, ECM trees acquired more P from a complex organic form (phytic acid). Most ECM tree species and all AM tree species also showed some capacity to take up simple organic P (monophosphate). Mycorrhizal colonisation was negatively correlated with soil extractable P concentration, suggesting that mycorrhizal fungi may regulate organic P acquisition among tree species. Our results support the hypothesis that ECM and AM plants partition soil P sources, which may play an ecologically important role in promoting species coexistence in tropical and subtropical forests.

Comparative Effectiveness of an mTOR-Based Systemic Therapy Regimen in Advanced, Metaplastic and Nonmetaplastic Triple-Negative Breast Cancer.

BACKGROUND: Triple-negative breast cancer (TNBC) is a heterogeneous disease with subtypes having different "targetable" molecular aberrations. Metaplastic breast cancers (MpBCs) are typically TNBCs and commonly have alterations in the PI3K/Akt/mTOR pathway. We previously reported efficacy for an mTOR-based chemotherapy regimen in MpBC. To determine if tumor subtype influences prognosis, we compared treatment outcomes of patients with MpBC with those of patients with nonmetaplastic TNBC receiving an mTOR-based systemic therapy regimen. PATIENTS AND METHODS: Patients with advanced MpBC and nonmetaplastic TNBC were treated at our institution from April 16, 2009, through November 4, 2014, using mTOR inhibition (temsirolimus or everolimus) with liposomal doxorubicin and bevacizumab (DAT/DAE). Median progression-free survival (PFS) and overall survival (OS) were estimated by the Kaplan-Meier method. Cox regression analyses were used to evaluate associations between tumor histology and outcomes. Multivariable models were adjusted for all covariates. RESULTS: Fourteen patients with nonmetaplastic TNBC and 59 patients with advanced MpBC were treated with DAT/DAE. MpBC patients were older (p = .002) and less likely to have a history of bevacizumab use (p = .023). Median PFS for the nonmetaplastic TNBC and MpBC patients was 2.5 months and 4.8 months, respectively. This difference in PFS was statistically significant on univariable (p = .006) but not multivariable analysis (p = .087). Median OS for the nonmetaplastic TNBC and MpBC patients was 3.7 months and 10.0 months, respectively (p = .0003). MpBC remained significantly associated with improved OS on multivariable analysis (p < .0001). CONCLUSION: In our study, DAT/DAE appeared to be more effective in MpBC compared with nonmetaplastic TNBC. These data support patient selection for targeted therapy in TNBC. IMPLICATIONS FOR PRACTICE: Metaplastic breast cancers (MpBCs) represent <1% of all breast cancers, demonstrate mesenchymal differentiation, and are typically resistant to chemotherapy. Patients with advanced MpBC treated with an mTOR-based systemic therapy regimen had better long-term outcomes compared with patients with nonmetaplastic triple-negative breast cancer treated with the same regimen, suggesting that metaplastic histology may predict benefit from agents targeting the PI3K/Akt/mTOR pathway.

In situ mycorrhizal function - knowledge gaps and future directions.

We know a lot about the potential functions of mycorrhizas, but whether or not these are realized in the field where plants simultaneously experience a range of biotic interactions and fluctuating abiotic conditions is more or less unknown. In this Viewpoint, we present findings from a literature survey of papers on mycorrhizal function published in New Phytologist during the past 30 years. This survey showed that most functional studies are still conducted under controlled conditions, target mostly arbuscular and ectomycorrhizas, and focus on nutrient and carbon dynamics of the symbiosis. We also share discussions from a workshop, 'In situ mycorrhizal function: how do we get relevant data from a messy world?', held at the 9th International Conference on Mycorrhiza (ICOM9) in August 2017. In this workshop, we examined possibilities and limitations of old and new techniques for field research, and participants expressed the need to learn more about fungal traits and how they may relate to function. We argue that moving mycorrhizal experiments into the field will allow us not only to quantify realized functions, but also to revisit old paradigms and possibly discover new functions.

Historical biome distribution and recent human disturbance shape the diversity of arbuscular mycorrhizal fungi.

The availability of global microbial diversity data, collected using standardized metabarcoding techniques, makes microorganisms promising models for investigating the role of regional and local factors in driving biodiversity. Here we modelled the global diversity of symbiotic arbuscular mycorrhizal (AM) fungi using currently available data on AM fungal molecular diversity (small subunit (SSU) ribosomal RNA (rRNA) gene sequences) in field samples. To differentiate between regional and local effects, we estimated species pools (sets of potentially suitable taxa) for each site, which are expected to reflect regional processes. We then calculated community completeness, an index showing the fraction of the species pool present, which is expected to reflect local processes. We found significant spatial variation, globally in species pool size, as well as in local and dark diversity (absent members of the species pool). Species pool size was larger close to areas containing tropical grasslands during the last glacial maximum, which are possible centres of diversification. Community completeness was greater in regions of high wilderness (remoteness from human disturbance). Local diversity was correlated with wilderness and current connectivity to mountain grasslands. Applying the species pool concept to symbiotic fungi facilitated a better understanding of how biodiversity can be jointly shaped by large-scale historical processes and recent human disturbance.

Sequence-based classification and identification of Fungi.

Fungal taxonomy and ecology have been revolutionized by the application of molecular methods and both have increasing connections to genomics and functional biology. However, data streams from traditional specimen- and culture-based systematics are not yet fully integrated with those from metagenomic and metatranscriptomic studies, which limits understanding of the taxonomic diversity and metabolic properties of fungal communities. This article reviews current resources, needs, and opportunities for sequence-based classification and identification (SBCI) in fungi as well as related efforts in prokaryotes. To realize the full potential of fungal SBCI it will be necessary to make advances in multiple areas. Improvements in sequencing methods, including long-read and single-cell technologies, will empower fungal molecular ecologists to look beyond ITS and current shotgun metagenomics approaches. Data quality and accessibility will be enhanced by attention to data and metadata standards and rigorous enforcement of policies for deposition of data and workflows. Taxonomic communities will need to develop best practices for molecular characterization in their focal clades, while also contributing to globally useful datasets including ITS. Changes to nomenclatural rules are needed to enable validPUBLICation of sequence-based taxon descriptions. Finally, cultural shifts are necessary to promote adoption of SBCI and to accord professional credit to individuals who contribute to community resources.

Biogeography of Paenibacillus larvae, the causative agent of American foulbrood, using a new multilocus sequence typing scheme.

American foulbrood is the most destructive brood disease of honeybees (Apis mellifera) globally. The absence of a repeatable, universal typing scheme for the causative bacterium Paenibacillus larvae has restricted our understanding of disease epidemiology. We have created the first multilocus sequence typing scheme (MLST) for P. larvae, which largely confirms the previous enterobacterial repetitive intergenic consensus (ERIC)-polymerase chain reaction (PCR)-based typing scheme's divisions while providing added resolution and improved repeatability. We have used the new scheme to determine the distribution and biogeography of 294 samples of P. larvae from across six continents. We found that of the two most epidemiologically important ERIC types, ERIC I was more diverse than ERIC II. Analysis of the fixation index (FST ) by distance suggested a significant relationship between genetic and geographic distance, suggesting that population structure exists in populations of P. larvae. Interestingly, this effect was only observed within the native range of the host and was absent in areas where international trade has moved honeybees and their disease. Correspondence analysis demonstrated similar sequence type (ST) distributions between native and non-native countries and that ERIC I and II STs mainly have differing distributions. The new typing scheme facilitates epidemiological study of this costly disease of a key pollinator.

Fungi in the future: interannual variation and effects of atmospheric change on arbuscular mycorrhizal fungal communities.

Understanding the natural dynamics of arbuscular mycorrhizal (AM) fungi and their response to global environmental change is essential for the prediction of future plant growth and ecosystem functions. We investigated the long-term temporal dynamics and effect of elevated atmospheric carbon dioxide (CO2 ) and ozone (O3 ) concentrations on AM fungal communities. Molecular methods were used to characterize the AM fungal communities of soybean (Glycine max) grown under elevated and ambient atmospheric concentrations of both CO2 and O3 within a free air concentration enrichment experiment in three growing seasons over 5 yr. Elevated CO2 altered the community composition of AM fungi, increasing the ratio of Glomeraceae to Gigasporaceae. By contrast, no effect of elevated O3 on AM fungal communities was detected. However, the greatest compositional differences detected were between years, suggesting that, at least in the short term, large-scale interannual temporal dynamics are stronger mediators than atmospheric CO2 concentrations of AM fungal communities. We conclude that, although atmospheric change may significantly alter AM fungal communities, this effect may be masked by the influences of natural changes and successional patterns through time. We suggest that changes in carbon availability are important determinants of the community dynamics of AM fungi.

Navigating the labyrinth: a guide to sequence-based, community ecology of arbuscular mycorrhizal fungi.

Data generated from next generation sequencing (NGS) will soon comprise the majority of information about arbuscular mycorrhizal fungal (AMF) communities. Although these approaches give deeper insight, analysing NGS data involves decisions that can significantly affect results and conclusions. This is particularly true for AMF community studies, because much remains to be known about their basic biology and genetics. During a workshop in 2013, representatives from seven research groups using NGS for AMF community ecology gathered to discuss common challenges and directions for future research. Our goal was to improve the quality and accessibility of NGS data for the AMF research community. Discussions spanned sampling design, sample preservation, sequencing, bioinformatics and data archiving. With concrete examples we demonstrated how different approaches can significantly alter analysis outcomes. Failure to consider the consequences of these decisions may compound bias introduced at each step along the workflow. The products of these discussions have been summarized in this paper in order to serve as a guide for any researcher undertaking NGS sequencing of AMF communities.

Extreme environments simplify reassembly of communities of arbuscular mycorrhizal fungi.

The ecological impacts of long-term (press) disturbance on mechanisms regulating the relative abundance (i.e., commonness or rarity) and temporal dynamics of species within a community remain largely unknown. This is particularly true for the functionally important arbuscular mycorrhizal (AM) fungi; obligate plant-root endosymbionts that colonize more than two-thirds of terrestrial plant species. Here, we use high-resolution amplicon sequencing to examine how AM fungal communities in a specific extreme ecosystem-mofettes or natural CO2 springs caused by geological CO2 exhalations-are affected by long-term stress. We found that in mofettes, specific and temporally stable communities form as a subset of the local metacommunity. These communities are less diverse and dominated by adapted, "stress tolerant" taxa. Those taxa are rare in control locations and more benign environments worldwide, but show a stable temporal pattern in the extreme sites, consistently dominating the communities in grassland mofettes. This pattern of lower diversity and high dominance of specific taxa has been confirmed as relatively stable over several sampling years and is independently observed across multiple geographic locations (mofettes in different countries). This study implies that the response of soil microbial community composition to long-term stress is relatively predictable, which can also reflect the community response to other anthropogenic stressors (e.g., heavy metal pollution or land use change). Moreover, as AM fungi are functionally differentiated, with different taxa providing different benefits to host plants, changes in community structure in response to long-term environmental change have the potential to impact terrestrial plant communities and their productivity.IMPORTANCEArbuscular mycorrhizal (AM) fungi form symbiotic relationships with more than two-thirds of plant species. In return for using plant carbon as their sole energy source, AM fungi improve plant mineral supply, water balance, and protection against pathogens. This work demonstrates the importance of long-term experiments to understand the effects of long-term environmental change and long-term disturbance on terrestrial ecosystems. We demonstrated a consistent response of the AM fungal community to a long-term stress, with lower diversity and a less variable AM fungal community over time under stress conditions compared to the surrounding controls. We have also identified, for the first time, a suite of AM fungal taxa that are consistently observed across broad geographic scales in stressed and anthropogenically heavily influenced ecosystems. This is critical because global environmental change in terrestrial ecosystems requires an integrative approach that considers both above- and below-ground changes and examines patterns over a longer geographic and temporal scale, rather than just single sampling events.

Dissemination of metaldehyde catabolic pathways is driven by mobile genetic elements in Proteobacteria.

Bioremediation of metaldehyde from drinking water using metaldehyde-degrading strains has recently emerged as a promising alternative. Whole-genome sequencing was used to obtain full genomes for metaldehyde degraders Acinetobacter calcoaceticus E1 and Sphingobium CMET-H. For the former, the genetic context of the metaldehyde-degrading genes had not been explored, while for the latter, none of the degrading genes themselves had been identified. In A. calcoaceticus E1, IS91 and IS6-family insertion sequences (ISs) were found surrounding the metaldehyde-degrading gene cluster located in plasmid pAME76. This cluster was located in closely-related plasmids and associated to identical ISs in most metaldehyde-degrading ß- and γ-Proteobacteria, indicating horizontal gene transfer (HGT). For Sphingobium CMET-H, sequence analysis suggested a phytanoyl-CoA family oxygenase as a metaldehyde-degrading gene candidate due to its close homology to a previously identified metaldehyde-degrading gene known as mahX. Heterologous gene expression in Escherichia coli alongside degradation tests verified its functional significance and the degrading gene homolog was henceforth called mahS. It was found that mahS is hosted within the conjugative plasmid pSM1 and its genetic context suggested a crossover between the metaldehyde and acetoin degradation pathways. Here, specific replicons and ISs responsible for maintaining and dispersing metaldehyde-degrading genes in α, ß and γ-Proteobacteria through HGT were identified and described. In addition, a homologous gene implicated in the first step of metaldehyde utilisation in an α-Proteobacteria was uncovered. Insights into specific steps of this possible degradation pathway are provided.

Soil macroaggregation drives sequestration of organic carbon and nitrogen with three-year grass-clover leys in arable rotations.

Conventional arable cropping with annual crops established by ploughing and harrowing degrades larger soil aggregates that contribute to storing soil organic carbon (SOC). The urgent need to increase SOC content of arable soils to improve their functioning and sequester atmospheric CO2 has motivated studies into the effects of reintroducing leys into long-term conventional arable fields. However, effects of short-term leys on total SOC accumulation have been equivocal. As soil aggregation may be important for carbon storage, we investigated the effects of arable-to-ley conversion on cambisol soil after three years of ley, on concentrations and stocks of SOC, nitrogen and their distributions in different sized water-stable aggregates. These values were benchmarked against soil from beneath hedgerow margins. SOC stocks (0-7 cm depth) rose from 20.3 to 22.6 Mg ha-1 in the arable-to-ley conversion, compared to 30 Mg ha-1 in hedgerows, but this 2.3 Mg ha-1 difference (or 0.77 Mg C ha-1 yr-1) was not significant). However, the proportion of large macroaggregates (> 2000 µm) increased 5.4-fold in the arable-to-ley conversion, recovering to similar abundance as hedgerow soils, driving near parallel increases in SOC and nitrogen within large macroaggregates (5.1 and 5.7-fold respectively). The total SOC (0-7 cm depth) stored in large macroaggregates increased from 2.0 to 9.6 Mg ha-1 in the arable-to-ley conversion, which no longer differed significantly from the 12.1 Mg ha-1 under hedgerows. The carbon therefore accumulated three times faster, at 2.53 Mg C ha-1 yr-1, in the large macroaggregates compared to the bulk soil. These findings highlight the value of monitoring large macroaggregate-bound SOC as a key early indicator of shifts in soil quality in response to change in field management, and the benefits of leys in soil aggregation, carbon accumulation, and soil functioning, providing justification for fiscal incentives that encourage wider use of leys in arable rotations.

Experimental evaluation of biological regeneration of arable soil: The effects of grass-clover leys and arbuscular mycorrhizal inoculants on wheat growth, yield, and shoot pathology.

Wheat yields have plateaued in the UK over the last 25 years, during which time most arable land has been annually cropped continuously with short rotations dominated by cereals. Arable intensification has depleted soil organic matter and biology, including mycorrhizas, which are affected by tillage, herbicides, and crop genotype. Here, we test whether winter wheat yields, mycorrhization, and shoot health can be improved simply by adopting less intensive tillage and adding commercial mycorrhizal inoculum to long-term arable fields, or if 3-year grass-clover leys followed direct drilling is more effective for biological regeneration of soil with reduced N fertiliser. We report a trial of mycorrhization, ear pathology, and yield performance of the parents and four double haploid lines from the Avalon x Cadenza winter wheat population in a long-term arable field that is divided into replicated treatment plots. These plots comprised wheat lines grown using ploughing or disc cultivation for 3 years, half of which received annual additions of commercial arbuscular mycorrhizal (AM) inoculum, compared to 3-year mown grass-clover ley plots treated with glyphosate and direct-drilled. All plots annually received 35 kg of N ha-1 fertiliser without fungicides. The wheat lines did not differ in mycorrhization, which averaged only 34% and 40% of root length colonised (RLC) in the ploughed and disc-cultivated plots, respectively, and decreased with inoculation. In the ley, RLC increased to 52%. Two wheat lines were very susceptible to a sooty ear mould, which was lowest in the ley, and highest with disc cultivation. AM inoculation reduced ear infections by >50% in the susceptible lines. In the ley, yields ranged from 7.2 to 8.3 t ha-1, achieving 92 to 106% of UK average wheat yield in 2018 (7.8 t ha-1) but using only 25% of average N fertiliser. Yields with ploughing and disc cultivation averaged only 3.9 and 3.4 t ha-1, respectively, with AM inoculum reducing yields from 4.3 to 3.5 t ha-1 in ploughed plots, with no effect of disc cultivation. The findings reveal multiple benefits of reintegrating legume-rich leys into arable rotations as part of a strategy to regenerate soil quality and wheat crop health, reduce dependence on nitrogen fertilisers, enhance mycorrhization, and achieve good yields.

What are mycorrhizal traits?

Traits are inherent properties of organisms, but how are they defined for organismal networks such as mycorrhizal symbioses? Mycorrhizal symbioses are complex and diverse belowground symbioses between plants and fungi that have proved challenging to fit into a unified and coherent trait framework. We propose an inclusive mycorrhizal trait framework that classifies traits as morphological, physiological, and phenological features that have functional implications for the symbiosis. We further classify mycorrhizal traits by location - plant, fungus, or the symbiosis - which highlights new questions in trait-based mycorrhizal ecology designed to charge and challenge the scientific community. This new framework is an opportunity for researchers to interrogate their data to identify novel insights and gaps in our understanding of mycorrhizal symbioses.

Local adaptation to soil hypoxia determines the structure of an arbuscular mycorrhizal fungal community in roots from natural CO2 springs.

The processes responsible for producing and maintaining the diversity of natural arbuscular mycorrhizal (AM) fungal communities remain largely unknown. We used natural CO(2) springs (mofettes), which create hypoxic soil environments, to determine whether a long-term, directional, abiotic selection pressure could change AM fungal community structure and drive the selection of particular AM fungal phylotypes. We explored whether those phylotypes that appear exclusively in hypoxic soils are local specialists or widespread generalists able to tolerate a range of soil conditions. AM fungal community composition was characterized by cloning, restriction fragment length polymorphism typing, and the sequencing of small subunit rRNA genes from roots of four plant species growing at high (hypoxic) and low (control) geological CO(2) exposure. We found significant levels of AM fungal community turnover (ß diversity) between soil types and the numerical dominance of two AM fungal phylotypes in hypoxic soils. Our results strongly suggest that direct environmental selection acting on AM fungi is a major factor regulating AM fungal communities and their phylogeographic patterns. Consequently, some AM fungi are more strongly associated with local variations in the soil environment than with their host plant's distribution.

Distinct seasonal assemblages of arbuscular mycorrhizal fungi revealed by massively parallel pyrosequencing.

• Understanding the dynamics of rhizosphere microbial communities is essential for predicting future ecosystem function, yet most research focuses on either spatial or temporal processes, ignoring combined spatio-temporal effects. • Using pyrosequencing, we examined the spatio-temporal dynamics of a functionally important community of rhizosphere microbes, the arbuscular mycorrhizal (AM) fungi. We sampled AM fungi from plant roots growing in a temperate grassland in a spatially explicit manner throughout a year. • Ordination analysis of the AM fungal assemblages revealed significant temporal changes in composition and structure. Alpha and beta diversity tended to be negatively correlated with the climate variables temperature and sunshine hours. Higher alpha diversity during colder periods probably reflects more even competitive interactions among AM fungal species under limited carbon availability, a conclusion supported by analysis of beta diversity which highlights how resource limitation may change localized spatial dynamics. • Results reveal distinct AM fungal assemblages in winter and summer at this grassland site. A seasonally changing supply of host-plant carbon, reflecting changes in temperature and sunshine hours, may be the driving force in regulating the temporal dynamics of AM fungal communities. Climate change effects on seasonal temperatures may therefore substantially alter future AM fungal community dynamics and ecosystem functioning.

Arable fields as potential reservoirs of biodiversity: Earthworm populations increase in new leys.

Managing soil to support biodiversity is important to sustain the ecosystem services provided by soils upon which society depends. There is increasing evidence that functional diversity of soil biota is important for ecosystem services, and has been degraded by intensive agriculture. Importantly, the spatial distribution of reservoirs of soil biota in and surrounding arable fields is poorly understood. In a field experiment, grass-clover ley strips were introduced into four arable fields which had been under continuous intensive/conventional arable rotation for more than 10 years. Earthworm communities in arable fields and newly established grass-clover leys, as well as field boundary land uses (hedgerows and grassy field margins), were monitored over 2 years after arable-to-ley conversions. Within 2 years, earthworm abundance in new leys was 732 ± 244 earthworms m-2, similar to that in field margin soils (619 ± 355 earthworms m-2 yr-1) and four times higher than in adjacent arable soil (185 ± 132 earthworms m-2). Relative to the arable soils, earthworm abundance under the new leys showed changes in community composition, structure and functional group, which were particularly associated with an increase in anecic earthworms; thus new leys became more similar to grassy field margins. Earthworm abundance was similar in new leys that were either connected to biodiversity reservoirs i.e. field margins and hedgerows, or not (installed earthworm barriers). This suggests that, for earthworm communities in typical arable fields, biodiversity reservoirs in adjacent field margins and hedgerows may not be critical for earthworm populations to increase. We conclude that the increase in earthworm abundance in the new leys observed over 2 years was driven by recruitment from the existing residual population in arable soils. Therefore, arable soils are also potential reservoirs of biodiversity.

Mechanistic strategies of microbial communities regulating lignocellulose deconstruction in a UK salt marsh.

BACKGROUND: Salt marshes are major natural repositories of sequestered organic carbon with high burial rates of organic matter, produced by highly productive native flora. Accumulated carbon predominantly exists as lignocellulose which is metabolised by communities of functionally diverse microbes. However, the organisms that orchestrate this process and the enzymatic mechanisms employed that regulate the accumulation, composition and permanence of this carbon stock are not yet known. We applied meta-exo-proteome proteomics and 16S rRNA gene profiling to study lignocellulose decomposition in situ within the surface level sediments of a natural established UK salt marsh. RESULTS: Our studies revealed a community dominated by Gammaproteobacteria, Bacteroidetes and Deltaproteobacteria that drive lignocellulose degradation in the salt marsh. We identify 42 families of lignocellulolytic bacteria of which the most active secretors of carbohydrate-active enzymes were observed to be Prolixibacteracea, Flavobacteriaceae, Cellvibrionaceae, Saccharospirillaceae, Alteromonadaceae, Vibrionaceae and Cytophagaceae. These families secreted lignocellulose-active glycoside hydrolase (GH) family enzymes GH3, GH5, GH6, GH9, GH10, GH11, GH13 and GH43 that were associated with degrading Spartina biomass. While fungi were present, we did not detect a lignocellulolytic contribution from fungi which are major contributors to terrestrial lignocellulose deconstruction. Oxidative enzymes such as laccases, peroxidases and lytic polysaccharide monooxygenases that are important for lignocellulose degradation in the terrestrial environment were present but not abundant, while a notable abundance of putative esterases (such as carbohydrate esterase family 1) associated with decoupling lignin from polysaccharides in lignocellulose was observed. CONCLUSIONS: Here, we identify a diverse cohort of previously undefined bacteria that drive lignocellulose degradation in the surface sediments of the salt marsh environment and describe the enzymatic mechanisms they employ to facilitate this process. Our results increase the understanding of the microbial and molecular mechanisms that underpin carbon sequestration from lignocellulose within salt marsh surface sediments in situ and provide insights into the potential enzymatic mechanisms regulating the enrichment of polyphenolics in salt marsh sediments. Video Abstract.