Detection and Analysis of Florfenicol Residues and Metabolites in Nile Tilapia (Oreochromis niloticus) Tissues Post-Oral Administration in Tropical Waters.

Water temperature is a critical environmental parameter that significantly influences fish metabolism. This study assessed the metabolism of florfenicol (FF) in tilapia (Oreochromis niloticus) at water temperatures typical of tropical and subtropical regions. Fish were treated with FF by oral administration of a dose of 10 mg kg-1 bw for 10 consecutive days. Fish fillet, liver, and kidney were sampled during the treatment phase (1, 5, and 10 days) and posttreatment (1, 2, 3, and 5 days after the last FF administration). FF, florfenicol amine (FFA), monochloro florfenicol (FFCl), and florfenicol alcohol (FFOH) were determined in the sampled tissues using a validated LC-LC-MS/MS method. The highest FF, FFA, and FFOH concentrations were determined on day 5 during the treatment phase. For FF, the concentration order is kidney > liver > fillet, while for the metabolites FFOH and FFA, the order is liver > kidney > fillet. In fillet and liver, the concentrations of FFOH were higher than the FFA concentrations, indicating that FFOH was the primary metabolite in these tissues. FFCl was only quantified at concentrations lower than 90 µg kg-1 in all tissues. The results indicated that FF can be readily absorbed and rapidly eliminated in tilapia cultivated in warm water environments. This study revealed FFOH as the primary and most persistent metabolite in tilapia farmed in warm water, followed by FFA.

Concepts and criteria defining emerging microbiome applications.

In recent years, microbiomes and their potential applications for human, animal or plant health, food production and environmental management came into the spotlight of major national and international policies and strategies. This has been accompanied by substantial R&D investments in both public and private sectors, with an increasing number of products entering the market. Despite widespread agreement on the potential of microbiomes and their uses across disciplines, stakeholders and countries, there is no consensus on what defines a microbiome application. This often results in non-comprehensive communication or insufficient documentation making commercialisation and acceptance of the novel products challenging. To showcase the complexity of this issue we discuss two selected, well-established applications and propose criteria defining a microbiome application and their conditions of use for clear communication, facilitating suitable regulatory frameworks and building trust among stakeholders.

Genomic and functional divergence of Staphylococcus aureus strains from atopic dermatitis patients and healthy individuals: insights from global and local scales.

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease worldwide and is characterized by a complex interplay with skin microbiota, with Staphylococcus aureus often abnormally more abundant in AD patients than in healthy individuals (HE). S. aureus harbors diverse strains with varied genetic compositions and functionalities, which exhibit differential connections with the severity of AD. However, the differences in S. aureus strains between AD and HE remain unclear, with most variations seen at a specific geographic level, implying spontaneous adaptations rather than systematic distinctions. This study presents genomic and functional differences between these S. aureus strains from AD and HE on both global and local levels. We observed reduced gene content diversity but increased functional variation in the global AD-associated strains. Two additional AD-dominant clusters emerged, with Cluster 1 enriched in transposases and Cluster 2 showcasing genes linked to adaptability and antibiotic resistance. Particularly, robust evidence illustrates that the lantibiotic operon of S. aureus, involved in the biosynthesis of lantibiotics, was acquired via horizontal gene transfer from environmental bacteria. Comparisons of the gene abundance profiles in functional categories also indicate limited zoonotic potential between human and animal isolates. Local analysis mirrored global gene diversity but showed distinct functional variations between AD and HE strains. Overall, this research provides foundational insights into the genomic evolution, adaptability, and antibiotic resistance of S. aureus, with significant implications for clinical microbiology.IMPORTANCEOur study uncovers significant genomic variations in Staphylococcus aureus strains associated with atopic dermatitis. We observed adaptive evolution tailored to the disease microenvironment, characterized by a smaller pan-genome than strains from healthy skin both on the global and local levels. Key functional categories driving strain diversification include "replication and repair" and "transporters," with transposases being pivotal. Interestingly, the local strains predominantly featured metal-related genes, whereas global ones emphasized antimicrobial resistances, signifying scale-dependent diversification nuances. We also pinpointed horizontal gene transfer events, indicating interactions between human-associated and environmental bacteria. These insights expand our comprehension of S. aureus's genetic adaptation in atopic dermatitis, yielding valuable implications for clinical approaches.

Quantification of florfenicol and its metabolites in fillets of Nile tilapia: Synthesis of metabolites and validation of an on-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry method.

This study concerns the synthesis of the florfenicol (FF) metabolites florfenicol amine (FFA), florfenicol alcohol (FFOH), and monochloroflorfenicol (FFCl), for their subsequent use as reference standards in On-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS) analysis. The metabolites were characterized using 1H and 13C NMR, as well as HRMS, and their purities were confirmed by quantitative NMR to ensure analytical reliability. Validation of the developed analytical method showed that it presented acceptable performance, with linearity >0.99 for all the target analytes, accuracies within ±10 % of nominal concentrations, and intra- and inter-day precisions within 15 %. Application of this method to fillets from fish that had been treated with florfenicol (dose of 10 mg/kg bw daily) demonstrated its effectiveness in consistently detecting FF and its metabolites throughout the treatment. The results emphasized the utility of the method for enhancing pharmacokinetic and residue depletion research. The ability to precisely monitor the drug and its metabolites in treated fish provides important insights into florfenicol metabolism, laying the groundwork for further comprehensive profiling studies of metabolites in fish tissue.

A salicylic acid-associated plant-microbe interaction attracts beneficial Flavobacterium sp. to the Arabidopsis thaliana phyllosphere.

Both above- and below-ground parts of plants are constantly challenged with microbes and interact closely with them. Many plant-growth-promoting rhizobacteria, mostly interacting with the plant's root system, enhance the immunity of plants in a process described as induced systemic resistance (ISR). Here, we characterized local induced resistance (IR) triggered by the model PGPR Pseudomonas simiae WCS417r (WCS417) in Arabidopsis thaliana. Hydroponic application of WCS417 to Arabidopsis roots resulted in propagation of WCS417 in/on leaves and the establishment of local IR. WCS417-triggered local IR was dependent on salicylic acid (SA) biosynthesis and signalling and on functional biosynthesis of pipecolic acid and monoterpenes, which are classically associated with systemic acquired resistance (SAR). WCS417-triggered local IR was further associated with a priming of gene expression changes related to SA signalling and SAR. A metabarcoding approach applied to the leaf microbiome revealed a significant local IR-associated enrichment of Flavobacterium sp.. Co-inoculation experiments using WCS417 and At-LSPHERE Flavobacterium sp. Leaf82 suggest that the proliferation of these bacteria is influenced by both microbial and immunity-related, plant-derived factors. Furthermore, application of Flavobacterium Leaf82 to Arabidopsis leaves induced SAR in an NPR1-dependent manner, suggesting that recruitment of this bacterium to the phyllosphere resulted in propagation of IR. Together, the data highlight the importance of plant-microbe-microbe interactions in the phyllosphere and reveal Flavobacterium sp. Leaf82 as a new beneficial promoter of plant health.

Air monitoring by nanopore sequencing.

While the air microbiome and its diversity are essential for human health and ecosystem resilience, comprehensive air microbial diversity monitoring has remained rare, so that little is known about the air microbiome's composition, distribution, or functionality. Here we show that nanopore sequencing-based metagenomics can robustly assess the air microbiome in combination with active air sampling through liquid impingement and tailored computational analysis. We provide fast and portable laboratory and computational approaches for air microbiome profiling, which we leverage to robustly assess the taxonomic composition of the core air microbiome of a controlled greenhouse environment and of a natural outdoor environment. We show that long-read sequencing can resolve species-level annotations and specific ecosystem functions through de novo metagenomic assemblies despite the low amount of fragmented DNA used as an input for nanopore sequencing. We then apply our pipeline to assess the diversity and variability of an urban air microbiome, using Barcelona, Spain, as an example; this randomized experiment gives first insights into the presence of highly stable location-specific air microbiomes within the city's boundaries, and showcases the robust microbial assessments that can be achieved through automatable, fast, and portable nanopore sequencing technology.

Distinct prophage gene profiles of Staphylococcus aureus strains from atopic dermatitis patients and healthy individuals.

Staphylococcus aureus strains exhibit varying associations with atopic dermatitis (AD), but the genetic determinants underpinning the pathogenicity are yet to be fully characterized. To reveal the genetic differences between S. aureus strains from AD patients and healthy individuals (HE), we developed and employed a random forest classifier to identify potential marker genes responsible for their phenotypic variations. The classifier was able to effectively distinguish strains from AD and HE. We also uncovered strong links between certain marker genes and phage functionalities, with phage holin emerging as the most pivotal differentiating factor. Further examination of S. aureus gene content highlighted the genetic diversity and functional implications of prophages in driving differentiation between strains from AD and HE. The HE group exhibited greater gene content diversity, largely influenced by their prophages. While strains from both AD and HE universally housed prophages, those in the HE group were distinctively higher at the strain level. Moreover, although prophages in the HE group exhibited variously higher enrichment of differential functions, the AD group displayed a notable enrichment of virulence factors within their prophages, underscoring the important contribution of prophages to the pathogenesis of AD-associated strains. Overall, prophages significantly shape the genetic and functional profiles of S. aureus strains, shedding light on their pathogenic potential and elucidating the mechanisms behind the phenotypic variations in AD and HE environments. IMPORTANCE: Through a nuanced exploration of Staphylococcus aureus strains obtained from atopic dermatitis (AD) patients and healthy controls (HE), our research unveils pivotal genetic determinants influencing their pathogenic associations. Utilizing a random forest classifier, we illuminate distinct marker genes, with phage holin emerging as a critical differential factor, revealing the profound impact of prophages on genetic and pathogenic profiles. HE strains exhibited a diverse gene content, notably shaped by unique, heightened prophages. Conversely, AD strains emphasized a pronounced enrichment of virulence factors within prophages, signifying their key role in AD pathogenesis. This work crucially highlights prophages as central architects of the genetic and functional attributes of S. aureus strains, providing vital insights into pathogenic mechanisms and phenotypic variations, thereby paving the way for targeted AD therapeutic approaches and management strategies by demystifying specific genetic and pathogenic mechanisms.

The effect of successive summer drought periods on bacterial diversity along a plant species richness gradient.

Drought is a major stressor to soil microbial communities, and the intensification of climate change is predicted to increase hydric stress worldwide in the coming decades. As a possible mitigating factor for the consequences of prolonged drought periods, above and belowground biodiversity can increase ecosystem resistance and resilience by improving metabolic redundancy and complementarity as biodiversity increases. Here, we investigated the interaction effect between plant richness and successive, simulated summer drought on soil microbial communities during a period of 9 years.To do that, we made use of a well-established biodiversity experiment (The Jena Experiment) to investigate the response of microbial richness and community composition to successive drought periods alongside a plant richness gradient, which covers 1-, 2-, 4-, 8-, 16-, and 60-species plant communities. Plots were covered from natural precipitation by installing rain shelters 6 weeks every summer. Bulk soil samples were collected 1 year after the last summer drought was simulated. Our data indicate that bacterial richness increased after successive exposure to drought, with the increase being stable along the plant richness gradient. We identified a significant effect of plant species richness on the soil microbial community composition and determined the taxa significantly impacted by drought at each plant richness level. Our data successfully demonstrates that summer drought might have a legacy effect on soil bacterial communities.

Comparative genomic analysis of strain Priestia megaterium B1 reveals conserved potential for adaptation to endophytism and plant growth promotion.

In our study, we aimed to explore the genomic and phenotypic traits of Priestia megaterium strain B1, which was isolated from root material of healthy apple plants, to adapt to the endophytic lifestyle and promote plant growth. We identified putative genes encoding proteins involved in chemotaxis, flagella biosynthesis, biofilm formation, secretory systems, detoxification, transporters, and transcription regulation. Furthermore, B1 exhibited both swarming and swimming motilities, along with biofilm formation. Both genomic and physiological analyses revealed the potential of B1 to promote plant growth through the production of indole-3-acetic acid and siderophores, as well as the solubilization of phosphate and zinc. To deduce potential genomic features associated with endophytism across members of P. megaterium strains, we conducted a comparative genomic analysis involving 27 and 31 genomes of strains recovered from plant and soil habitats, respectively, in addition to our strain B1. Our results indicated a closed pan genome and comparable genome size of strains from both habitats, suggesting a facultative host association and adaptive lifestyle to both habitats. Additionally, we performed a sparse Partial Least Squares Discriminant Analysis to infer the most discriminative functional features of the two habitats based on Pfam annotation. Despite the distinctive clustering of both groups, functional enrichment analysis revealed no significant enrichment of any Pfam domain in both habitats. Furthermore, when assessing genetic elements related to adaptation to endophytism in each individual strain, we observed their widespread presence among strains from both habitats. Moreover, all members displayed potential genetic elements for promoting plant growth.IMPORTANCEBoth genomic and phenotypic analyses yielded valuable insights into the capacity of P. megaterium B1 to adapt to the plant niche and enhance its growth. The comparative genomic analysis revealed that P. megaterium members, whether derived from soil or plant sources, possess the essential genetic machinery for interacting with plants and enhancing their growth. The conservation of these traits across various strains of this species extends its potential application as a bio-stimulant in diverse environments. This significance also applies to strain B1, particularly regarding its application to enhance the growth of plants facing apple replant disease conditions.

The rhizosphere microbiome of 51 potato cultivars with diverse plant growth characteristics.

Rhizosphere microbial communities play a substantial role in plant productivity. We studied the rhizosphere bacteria and fungi of 51 distinct potato cultivars grown under similar greenhouse conditions using a metabarcoding approach. As expected, individual cultivars were the most important determining factor of the rhizosphere microbial composition; however, differences were also obtained when grouping cultivars according to their growth characteristics. We showed that plant growth characteristics were related to deterministic and stochastic assembly processes of bacterial and fungal communities, respectively. The bacterial genera Arthrobacter and Massilia (known to produce indole acetic acid and siderophores) exhibited greater relative abundance in high- and medium-performing cultivars. Bacterial co-occurrence networks were larger in the rhizosphere of these cultivars and were characterized by a distinctive combination of plant beneficial Proteobacteria and Actinobacteria along with a module of diazotrophs namely Azospira, Azoarcus, and Azohydromonas. Conversely, the network within low-performing cultivars revealed the lowest nodes, hub taxa, edges density, robustness, and the highest average path length resulting in reduced microbial associations, which may potentially limit their effectiveness in promoting plant growth. Our findings established a clear pattern between plant productivity and the rhizosphere microbiome composition and structure for the investigated potato cultivars, offering insights for future management practices.

The impact of high-salt diet on asthma in humans and mice: Effect on specific T-cell signatures and microbiome.

BACKGROUND: The rise in asthma has been linked to different environmental and lifestyle factors including dietary habits. Whether dietary salt contributes to asthma incidence, remains controversial. We aimed to investigate the impact of higher salt intake on asthma incidence in humans and to evaluate underlying mechanisms using mouse models. METHODS: Epidemiological research was conducted using the UK Biobank Resource. Data were obtained from 42,976 participants with a history of allergies. 24-h sodium excretion was estimated from spot urine, and its association with asthma incidence was assessed by Cox regression, adjusting for relevant covariates. For mechanistic studies, a mouse model of mite-induced allergic airway inflammation (AAI) fed with high-salt diet (HSD) or normal-salt chow was used to characterize disease development. The microbiome of lung and feces (as proxy for gut) was analyzed via 16S rRNA gene based metabarcoding approach. RESULTS: In humans, urinary sodium excretion was directly associated with asthma incidence among females but not among males. HSD-fed female mice displayed an aggravated AAI characterized by increased levels of total IgE, a TH2-TH17-biased inflammatory cell infiltration accompanied by upregulation of osmosensitive stress genes. HSD induced distinct changes in serum short chain fatty acids and in both gut and lung microbiome, with a lower Bacteroidetes to Firmicutes ratio and decreased Lactobacillus relative abundance in the gut, and enriched members of Gammaproteobacteria in the lung. CONCLUSIONS: High dietary salt consumption correlates with asthma incidence in female adults with a history of allergies. Female mice revealed HSD-induced T-cell lung profiles accompanied by alterations of gut and lung microbiome.

Rhizosphere competent inoculants modulate the apple root-associated microbiome and plant phytoalexins.

Modulating the soil microbiome by applying microbial inoculants has gained increasing attention as eco-friendly option to improve soil disease suppressiveness. Currently, studies unraveling the interplay of inoculants, root-associated microbiome, and plant response are lacking for apple trees. Here, we provide insights into the ability of Bacillus velezensis FZB42 or Pseudomonas sp. RU47 to colonize apple root-associated microhabitats and to modulate their microbiome. We applied the two strains to apple plants grown in soils from the same site either affected by apple replant disease (ARD) or not (grass), screened their establishment by selective plating, and measured phytoalexins in roots 3, 16, and 28 days post inoculation (dpi). Sequencing of 16S rRNA gene and ITS fragments amplified from DNA extracted 28 dpi from different microhabitat samples revealed significant inoculation effects on fungal ß-diversity in root-affected soil and rhizoplane. Interestingly, only in ARD soil, most abundant bacterial amplicon sequence variants (ASVs) changed significantly in relative abundance. Relative abundances of ASVs affiliated with Enterobacteriaceae were higher in rhizoplane of apple grown in ARD soil and reduced by both inoculants. Bacterial communities in the root endosphere were not affected by the inoculants but their presence was indicated. Interestingly and previously unobserved, apple plants responded to the inoculants with increased phytoalexin content in roots, more pronounced in grass than ARD soil. Altogether, our results indicate that FZB42 and RU47 were rhizosphere competent, modulated the root-associated microbiome, and were perceived by the apple plants, which could make them interesting candidates for an eco-friendly mitigation strategy of ARD. KEY POINTS: • Rhizosphere competent inoculants modulated the microbiome (mainly fungi) • Inoculants reduced relative abundance of Enterobacteriaceae in the ARD rhizoplane • Inoculants increased phytoalexin content in roots, stronger in grass than ARD soil.

Climate change disrupts the seasonal coupling of plant and soil microbial nutrient cycling in an alpine ecosystem.

The seasonal coupling of plant and soil microbial nutrient demands is crucial for efficient ecosystem nutrient cycling and plant production, especially in strongly seasonal alpine ecosystems. Yet, how these seasonal nutrient cycling processes are modified by climate change and what the consequences are for nutrient loss and retention in alpine ecosystems remain unclear. Here, we explored how two pervasive climate change factors, reduced snow cover and shrub expansion, interactively modify the seasonal coupling of plant and soil microbial nitrogen (N) cycling in alpine grasslands, which are warming at double the rate of the global average. We found that the combination of reduced snow cover and shrub expansion disrupted the seasonal coupling of plant and soil N-cycling, with pronounced effects in spring (shortly after snow melt) and autumn (at the onset of plant senescence). In combination, both climate change factors decreased plant organic N-uptake by 70% and 82%, soil microbial biomass N by 19% and 38% and increased soil denitrifier abundances by 253% and 136% in spring and autumn, respectively. Shrub expansion also individually modified the seasonality of soil microbial community composition and stoichiometry towards more N-limited conditions and slower nutrient cycling in spring and autumn. In winter, snow removal markedly reduced the fungal:bacterial biomass ratio, soil N pools and shifted bacterial community composition. Taken together, our findings suggest that interactions between climate change factors can disrupt the temporal coupling of plant and soil microbial N-cycling processes in alpine grasslands. This could diminish the capacity of these globally widespread alpine ecosystems to retain N and support plant productivity under future climate change.

Comparative Metagenomic Analysis of Bacteriophages and Prophages in Gnotobiotic Mouse Models.

Gnotobiotic murine models are important to understand microbiota-host interactions. Despite the role of bacteriophages as drivers for microbiome structure and function, there is no information about the structure and function of the gut virome in gnotobiotic models and the link between bacterial and bacteriophage/prophage diversity. We studied the virome of gnotobiotic murine Oligo-MM12 (12 bacterial species) and reduced Altered Schaedler Flora (ASF, three bacterial species). As reference, the virome of Specific Pathogen-Free (SPF) mice was investigated. A metagenomic approach was used to assess prophages and bacteriophages in the guts of 6-week-old female mice. We identified a positive correlation between bacteria diversity, and bacteriophages and prophages. Caudoviricetes (82.4%) were the most prominent class of phages in all samples with differing relative abundance. However, the host specificity of bacteriophages belonging to class Caudoviricetes differed depending on model bacterial diversity. We further studied the role of bacteriophages in horizontal gene transfer and microbial adaptation to the host's environment. Analysis of mobile genetic elements showed the contribution of bacteriophages to the adaptation of bacterial amino acid metabolism. Overall, our results implicate virome "dark matter" and interactions with the host system as factors for microbial community structure and function which determine host health. Taking the importance of the virome in the microbiome diversity and horizontal gene transfer, reductions in the virome might be an important factor driving losses of microbial biodiversity and the subsequent dysbiosis of the gut microbiome.

The seeds of Plantago lanceolata comprise a stable core microbiome along a plant richness gradient.

BACKGROUND: Seed endophytic bacteria are beneficial to plants. They improve seedling growth by enhancing plant nutrient uptake, modulating stress-related phytohormone production, and targeting pests and pathogens with antibiotics. Seed endophyte composition can be influenced by pollination, plant cultivar, and soil physicochemical conditions. However, the effects of plant community richness on seed endophytes are unknown. To investigate the effects of increasing plant species richness on the diversity and composition of the seed microbiome, we made use of a well-established long-term biodiversity experiment in Germany (The Jena Experiment). We sampled seeds from different Plantago lanceolata blossoms in a plant diversity gradient ranging from monoculture to 16 species mixtures. The seeds were surface sterilized to remove seed surface-associated bacteria and subjected to a metabarcoding approach to assess bacterial community structure. RESULTS: Our data indicate a very stable core microbiome, which accounted for more than 90% of the reads and was present in all seeds independent of the plant richness level the seeds originated from. It consisted mainly of reads linked to Pseudomonas rhizosphaerae, Sphingomonas faeni and Pirellulla spp. 9% of the obtained reads were not part of the core microbiome and were only present in plots of specific diversity levels. The number of unique ASVs was positively correlated with plant richness. Interestingly, most reads described as non-core members belonged to the same genera described as the core microbiome, indicating the presence of different strains or species with possibly different functional properties important for seed performance. CONCLUSION: Our data indicate that Plantago lanceolata maintains a large seeds core microbiome across the plant richness gradient. However, the number of unique ASVs increases alongside the plant community richness, indicating that ecosystem biodiversity also mitigates diversity loss in seed endophytes.

(Pan)genomic analysis of two Rhodococcus isolates and their role in phenolic compound degradation.

The genus Rhodococcus is recognized for its potential to degrade a large range of aromatic substances, including plant-derived phenolic compounds. We used comparative genomics in the context of the broader Rhodococcus pan-genome to study genomic traits of two newly described Rhodococcus strains (type-strain Rhodococcus pseudokoreensis R79T and Rhodococcus koreensis R85) isolated from apple rhizosphere. Of particular interest was their ability to degrade phenolic compounds as part of an integrated approach to treat apple replant disease (ARD) syndrome. The pan-genome of the genus Rhodococcus based on 109 high-quality genomes was open with a small core (1.3%) consisting of genes assigned to basic cell functioning. The range of genome sizes in Rhodococcus was high, from 3.7 to 10.9 Mbp. Genomes from host-associated strains were generally smaller compared to environmental isolates which were characterized by exceptionally large genome sizes. Due to large genomic differences, we propose the reclassification of distinct groups of rhodococci like the Rhodococcus equi cluster to new genera. Taxonomic species affiliation was the most important factor in predicting genetic content and clustering of the genomes. Additionally, we found genes that discriminated between the strains based on habitat. All members of the genus Rhodococcus had at least one gene involved in the pathway for the degradation of benzoate, while biphenyl degradation was mainly restricted to strains in close phylogenetic relationships with our isolates. The ~40% of genes still unclassified in larger Rhodococcus genomes, particularly those of environmental isolates, need more research to explore the metabolic potential of this genus.IMPORTANCERhodococcus is a diverse, metabolically powerful genus, with high potential to adapt to different habitats due to the linear plasmids and large genome sizes. The analysis of its pan-genome allowed us to separate host-associated from environmental strains, supporting taxonomic reclassification. It was shown which genes contribute to the differentiation of the genomes based on habitat, which can possibly be used for targeted isolation and screening for desired traits. With respect to apple replant disease (ARD), our isolates showed genome traits that suggest potential for application in reducing plant-derived phenolic substances in soil, which makes them good candidates for further testing against ARD.

A slow-fast trait continuum at the whole community level in relation to land-use intensification.

Organismal functional strategies form a continuum from slow- to fast-growing organisms, in response to common drivers such as resource availability and disturbance. However, whether there is synchronisation of these strategies at the entire community level is unclear. Here, we combine trait data for >2800 above- and belowground taxa from 14 trophic guilds spanning a disturbance and resource availability gradient in German grasslands. The results indicate that most guilds consistently respond to these drivers through both direct and trophically mediated effects, resulting in a 'slow-fast' axis at the level of the entire community. Using 15 indicators of carbon and nutrient fluxes, biomass production and decomposition, we also show that fast trait communities are associated with faster rates of ecosystem functioning. These findings demonstrate that 'slow' and 'fast' strategies can be manifested at the level of whole communities, opening new avenues of ecosystem-level functional classification.

Long-term conservation tillage with reduced nitrogen fertilization intensity can improve winter wheat health via positive plant-microorganism feedback in the rhizosphere.

Microbiome-based solutions are regarded key for sustainable agroecosystems. However, it is unclear how agricultural practices affect the rhizosphere microbiome, plant-microorganism interactions and crop performance under field conditions. Therefore, we installed root observation windows in a winter wheat field cultivated either under long-term mouldboard plough (MP) or cultivator tillage (CT). Each tillage practice was also compared at two nitrogen (N) fertilization intensities, intensive (recommended N-supply with pesticides/growth regulators) or extensive (reduced N-supply, no fungicides/growth regulators). Shoot biomass, root exudates and rhizosphere metabolites, physiological stress indicators, and gene expression were analyzed together with the rhizosphere microbiome (bacterial/archaeal 16S rRNA gene, fungal ITS amplicon, and shotgun metagenome sequencing) shortly before flowering. Compared to MP, the rhizosphere of CT winter wheat contained more primary and secondary metabolites, especially benzoxazinoid derivatives. Potential copiotrophic and plant-beneficial taxa (e.g. Bacillus, Devosia, and Trichoderma) as well as functional genes (e.g. siderophore production, trehalose synthase, and ACC deaminase) were enriched in the CT rhizosphere, suggesting that tillage affected belowground plant-microorganism interactions. In addition, physiological stress markers were suppressed in CT winter wheat compared to MP. In summary, tillage practice was a major driver of crop performance, root deposits, and rhizosphere microbiome interactions, while the N-fertilization intensity was also relevant, but less important.

Identification of Huge Phages from Wastewater Metagenomes.

Huge phages have genomes larger than 200 kilobases, which are particularly interesting for their genetic inventory and evolution. We screened 165 wastewater metagenomes for the presence of viral sequences. After identifying over 600 potential huge phage genomes, we reduced the dataset using manual curation by excluding viral contigs that did not contain viral protein-coding genes or consisted of concatemers of several small phage genomes. This dataset showed seven fully annotated huge phage genomes. The phages grouped into distinct phylogenetic clades, likely forming new genera and families. A phylogenomic analysis between our huge phages and phages with smaller genomes, i.e., less than 200 kb, supported the hypothesis that huge phages have undergone convergent evolution. The genomes contained typical phage protein-coding genes, sequential gene cassettes for metabolic pathways, and complete inventories of tRNA genes covering all standard and rare amino acids. Our study showed a pipeline for huge phage analyses that may lead to new enzymes for therapeutic or biotechnological applications.