FEMS Microbiology Letters

Sinorhizobium meliloti is a nitrogen-fixing soil bacterium that forms a facultative mutualism with its host alfalfa. S. meliloti strains exhibit diverse colony morphologies on solid culture media that span a continuum from dry to mucoid. Studies on how this trait affects symbiosis rely on mutations in exopolysaccharide II production genes; however, whether natural variation in morphology confers a selective advantage on rhizobia in their natural habitats remains unknown. Here, we used 90 mucoid and 27 dry natural isolates to test whether colony morphology is associated with rhizobial fitness in the soil and in the host, or with the nitrogen-fixation benefits they provide to the plant. Colony morphologies were widely distributed across a phylogenetic tree, suggesting that morphological shifts occurred repeatedly and no single genetic variant was strongly associated with this trait. We inoculated soil mesocosms and plants with a mixture of dry and mucoid bacteria. We observed that dry rhizobia have higher fitness, particularly at 22{degrees}C and 32{degrees}C, but not under cold or drought conditions, independent of the initial rhizobial load. Conversely, mucoid bacteria have a modestly higher relative fitness in host nodules, and single inoculations showed that they tend to confer greater benefits to all three alfalfa varieties. Over time, we also observed rare, repeated conversion from mucoid to dry morphologies in soil and host plants. Taken together, our study reveals that morphological variation within a species in a single agricultural field is important for bacterial fitness in the soil and can have cascading effects on the rhizobia's plant benefits.

Vibrio cholerae, the facultative pathogen underlying cholera, naturally inhabits warm aquatic estuaries. Environmental persistence is enhanced by the ability of V. cholerae to colonize host reservoirs and form multicellular biofilms, causing seasonally endemic outbreaks in many tropical regions. Most toxigenic strains utilize the type IVa mannose-sensitive hemagglutinin (MSHA) pilus for host reservoir colonization and biofilm formation. Temperature and salinity can alter V. cholerae biofilm formation, yet their impact on MSHA production specifically remains largely unknown. Here, we utilized transcriptional reporters of predicted msh promoters (msh-P1/msh-P2/msh-P3) and functional assays, to determine temperature and salinity impacts on msh expression and pilus biogenesis. Under standard laboratory conditions (30{degrees}C, 1% NaCl) only msh-P1/P2 are active and inversely-coordinated with one another. Both msh-P1/P2 activity were elevated by high temperature (37{degrees}C) and low salinity (0.25%/0.5% NaCl), and reduced by low temperature (20{degrees}C/25{degrees}C) and high salinity (2%/3% NaCl). Temperature-mediated alterations in promoter activity were not immediately reflected in changes to cell-surface MSHA levels, whereas high salinity led to decreased MSHA production. Combining high temperature (37{degrees}C) and high salinity (2%/3% NaCl), attenuated the salinity-mediated reduction of msh-P1/P2 activity. Biofilm biomass levels were only substantially heightened at 25{degrees}C and 20{degrees}C, likely a result of no temperature-dependent changes in cell-surface MSHA, and additional temperature-controlled biofilm regulation previously described. We also found msh-P1/P2 promoter activity and MSHA production varies widely across toxigenic O1 and O139 serogroups despite complete sequence homology. These results shed new light on how key signals regulate MSHA pilus production to support V. cholerae persistence in aquatic environments.

Metacaspases are cysteine proteases and are found in every group of organisms except animals. They are structural orthologs of caspases, which orchestrate apoptosis in animals. Caspases, metacaspases, paracaspases and orthocaspases are class C14 proteases with a similar active site (the hemoglobinase fold) and a catalytic cysteine residue. However, metacaspases cleave after arginine and lysine instead of aspartate and some researchers point out that a name ending with caspase is unsuitable. Also, most metacaspases are activated by calcium, they do not target the same proteins as caspases and they cut multiply instead of once. The Candida albicans metacaspase Mca1p mediates cell death in response to various stresses but also has pro-life functions. Many plant and protist metacaspases lack cell death roles and are involved in development, differentiation and immunity. This article highlights an interesting phenomenon, whereby the promotion of stress sensitivity and reduction of virulence, by Mca1p in C. albicans cells from exponential culture are abolished and reversed, respectively in cells from stationary-phase culture. This hints at the proteases's dual nature and at the conditions that might initiate a switch between pro-life and pro-death functions.

Jeongeupia sacculi (HS-3) is a novel {beta}-proteobacterium with a unique multicellular life cycle. The genetic tractability and mechanisms underlying differentiation are unknown. Here, we adapt a method of homologous recombination for genetic modification in HS-3 and generate a disruption mutant of rpoS, which encodes the alternative sigma factor{sigma} S commonly associated with general stress response or major behavioral switches. We then characterize phenotypes associated with rpoS disruption. Under low-nutrient conditions, rpoS disruption reduced Congo red binding, consistent with rpoS acting as a regulator of low-nutrient response by upregulating production of biofilm-associated materials. Surprisingly, rpoS disruption did not significantly alter survival in response to other stressors in general stress response assays tested. Our work establishes a method for genetic manipulation in HS-3 and enables future investigation into the life cycle of HS-3, including whether rpoS has a role in differentiation triggered by low-nutrient response.

A subgroup of membrane-anchored bacterial Alkaline Phosphatase superfamily members transfers phospholipid headgroups from phospholipids to diverse acceptor molecules. As part of type II and hybrid type I/II cellulose biosynthesis gene clusters BcsG transfers phosphorylethanolamine pEtN from phospholipid to the emerging 1,4 {beta}-D-glucan chain synthesized by the BcsABC cellulose biosynthesis nanomachine. BcsG homologs throughout the phylogenetic tree possess a uniquely structured tripartite linker that connects the fifth transmembrane domain with the periplasmic catalytic domain. A N-terminal unstructured sequence of highly variable length and biased amino acid composition, the N-linker, is followed by an -helix and an unstructured sequence of high similarity and constant length leading into the first {beta}-strand of the catalytic domain. With BcsG from Salmonella typhimurium synthesizing pEtN cellulose as a model, linkers were shown to be promiscuous and linker length positively correlated with transfer efficiency of the pEtN headgroup and protein stability. As the donor substrate, the phosphatidylethanolamine content of the membranes affects pEtN transfer efficiency. With Alkaline Phosphatase superfamily members to be promiscuous enzymes the catalytic domain of OpgE transfers pEtN to osmoregulated periplasmic glucan. BcsG-OpgE hybrid proteins cause colony morphology alterations thus potentially transferring pEtN to the BcsA synthesized glucan chain. With BcsG with shortest linkers not associated with a cellulose biosynthesis gene cluster, multiple hypotheses can be proposed that select for different length of the N-linker in BcsG homologs located within a cellulose biosynthesis gene cluster in other Pseudomonadati.

Biofilm formation by the fungal pathogen Candida albicans is a major source of infection. The biofilm regulator Ume6 forms complexes with partner transcription factors Efg1, Ndt80, and Upc2 to drive expression of biofilm-related genes. Here we present chromatin immunoprecipitation with sequencing (ChIP-seq) data for Ume6-chromatin association in both wild-type and efg1{Delta}/{Delta} ndt80{Delta}/{Delta} upc2{Delta}/{Delta} backgrounds. Ume6 associates with two promoter region classes. For one class, Ume6 association is significantly decreased in the efg1{Delta}/{Delta} ndt80{Delta}/{Delta} upc2{Delta}/{Delta} background. This class includes 577 genes, many with well-established roles in biofilm formation or the related process of filamentation. For the second class, Ume6 association is unperturbed in the triple mutant background. This class includes 534 genes, some with roles in iron homeostasis (e.g., SFU1) and ergosterol synthesis (e.g., ERG11), which may contribute to the impact of Ume6 on ndt80{Delta}/{Delta} mutant azole drug sensitivity. It also includes FLO9, a putative adhesin gene that is required for the emergent biofilm state produced by efg1{Delta}/{Delta} ndt80{Delta}/{Delta} double mutants. The data show that Ume6 binding to ~half of its targets requires known partners, and Ume6 binding to ~half of its targets does not. Ume6 may bind to the latter set of promoter regions independently of any partner, or perhaps with additional partners that have yet to be discovered.

Carbohydrate inducible promoters on expression plasmids are widely used for biotechnology and basic science research. However, using carbohydrates for inducers has drawbacks including influencing bacterial metabolism, the inducer being used as a carbon source by the bacteria, high background expression, and only a subset of cells experiencing promoter activation. Furthermore, some bacteria including the pathogen Acinetobacter baumannii currently lack good carbohydrate-inducible promoters. To address this issue, a tetracycline-inducible promoter, PtetB, isolated from A. baumannii was cloned and evaluated in a number of important bacteria: Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Serratia marcescens. A highly sensitive luxCDABE reporter was used to evaluate promoter activity. S. marcescens strains with elevated and reduced cyclic-AMP levels were used to evaluate the impact of cAMP on PtetB function. The PtetB promoter was induced over 800-fold in A. baumannii and 10-750-fold inducible in the other tested species. Background expression was lower from PtetB in the pseudomonads than previously described carbohydrate inducible promoters. Data indicated that the PtetB promoter system may be a useful tool for future basic science research with the tested bacteria.

Metals are essential for all forms of life and are therefore the subject of tight competition at the host-pathogen interface. Manganese (Mn) is an important cofactor for enzymes involved in various processes in bacteria, including the response to oxidative stress, and the ability to scavenge Mn through the expression of high-affinity Mn transporters has been associated with virulence of many extracellular and vacuolar pathogens. While the cytosol has been established to be restrictive for growth of non-adapted pathogens, the extent to which metal limitation contributes to this is not well understood. Here, we investigate whether high-affinity Mn acquisition is important for intracellular adaptation and virulence of the cytosolic pathogen Listeria monocytogenes (Lmo). To do so, we generated a strain of Lmo in which both of its predicted high-affinity Mn transporters, MntH and MntABC, are disrupted. We found that this strain was severely defective in growth in vitro under Mn-limited conditions and had lower intracellular Mn content. Additionally, we observed Mn-dependent transcriptional regulation of the mntH and mntA genes. Together, these data strongly support that MntH and MntABC are high-affinity Mn transporters and are likely to be the only such dedicated Mn transporters expressed in Lmo. Using the {Delta}mntH {Delta}mntA strain, we provide evidence that Mn limitation sensitizes Lmo to oxidative stress in vitro, consistent with the known role of Mn in mitigating reactive oxygen species. Ultimately, we demonstrate that expression of high-affinity Mn transporters is essential for intracellular replication of Lmo in macrophages, plaquing on fibroblast monolayers, and for virulence in an animal model of systemic infection. Our work, therefore, suggests that Lmo is challenged by Mn limitation in the cytosol and requires Mn scavenging to adapt to its intracellular niche.

Four rhizobial strains isolated from root nodules of tropical leguminous plants in Costa Rica were characterized. Strain LEGMi-135b was isolated from Lonchocarpus felipei root nodules, LEGMi-12c from Cojoba arborea, LEGMi-198b from Calliandra haematocephala and Rhizobium altiplani LEGMi-166a from Mimosa pigra. Phylogenetic analyses based on the 16S rRNA gene and four concatenated housekeeping genes (recA, atpD, GATase and gyrB) placed these strains within the genera Martinezella (LEGMi-12c, LEGMi-135b, and LEGMi-198b) and Rhizobium (LEGMi-166a). Genome-based analyses showed that strain LEGMi-135b exhibited an average nucleotide identity (ANI) value of 94% and a digital DNA-DNA hybridization (dDDH) value of 53.2% compared with its closest related species, Martinezella hainanensis CCBAU 57015T, supporting its classification as a distinct species. LEGMI-12c exhibited ANI and dDDH values of 98% and 87%, respectively, compared with Martinezella hainanensis CCBAU 57015T. LEGMi-198b showed the highest similarity to Rhizobium cerradonense CNPSo 3464, with ANI and dDDH values of 98% and 81.4%, respectively; however, this taxon has not been validly published. LEGMi-166a exhibited ANI and dDDH values of 100% and 99.3%, respectively, compared with Rhizobium altiplani BR 10423, confirming its assignment to this species. Additionally, differentiation of strains LEGMi-135b and LEGMi-198b from their closest phylogenetic relatives was supported by phenotypic, physiological, and biochemical analyses. Based on the combined genomic, phenotypic, and biochemical evidence, we propose the establishment of the novel rhizobial species Martinezella legmii sp. nov., with strain LEGMi-135b designated as the type strain (LEGMi-135b), and Martinezella ivanii sp. nov., with strain LEGMi-198b designated as the type strain (LEGMi-198b). This study expands our understanding of rhizobial diversity associated with nitrogen-fixing symbioses, particularly among tropical leguminous plants from Costa Rica

Little is currently known about the regulation of PL fimbriae produced by some pathogenic E. coli strains. We identified PlfB, a transcriptional regulator of the PapB family, as a negative regulator of PL fimbriae (Plf). Deletion of plfB significantly increased plfA transcription and Plf production. PlfB bound specifically to the plfA promoter region. Using a PplfA-lux reporter system, the deletion of plfB caused sustained and increased expression across serial passages. Global regulatory genes such as lrp, argR, and hns were also implicated in regulation of plf expression. Loss of lrp or argR decreased plf expression, suggesting these regulators positively regulate PL fimbriae. By contrast, loss of hns increased levels of plf expression, supporting its role as a negative regulator. Interestingly, loss of plfB significantly increased bacterial colonization in the lung of 6-day-old turkey poults. Further, complementation of plfB restored plf fimbrial expression and colonization of turkey lungs to wild-type levels. This further supports an important role for PL fimbriae for colonization of turkey lungs, since loss of plfB which resulted in increased plf gene expression in turkey lungs also correlated with higher bacterial numbers in the lungs. Taken together, these results indicate that PlfB acts as a negative regulator to reduce levels of PL fimbrial expression, under some conditions, but that it is not required for plf expression. This contrasts with the role the PapB regulator, which has been shown to play an essential role in expression of P fimbriae in uropathogenic E. coli strains.

Bacteria utilize specialized protein secretion systems, particularly the type VI secretion system (T6SS), to dominate interbacterial competitions and kill the prey bacteria in a contact-dependent manner. Here, we report that disruption of the thioesterase gene encoded in the gramibactin (a bacterial siderophore) biosynthetic gene cluster activates the T6SS in the Burkholderia gladioli strain NGJ1, even in the absence of prey. The thioesterase mutant exhibits enhanced antibacterial activity, and ectopic expression of the gene complements the phenotype. Notably, thio mutant as well as thioesterase-complement strains show enhanced sensitivity to oxidative stress. The qRT-PCR analysis showed that the thio mutant had upregulated expression of RpoN1, a sigma factor, which positively regulates T6SS functions. We demonstrate that rpoN1 mutant is hypersensitive to oxidative stress and defective in T6SS activation, whereas overexpression of RpoN1 enhances oxidative stress tolerance in NGJ1 and activates T6SS. We propose that, during interbacterial conflicts encountered during plant colonization, NGJ1 faces an oxidative-stress-enriched environment that modulates thioesterase expression, induces RpoN1, and activates T6SS. Overall, our study exemplifies the broader physiological role of Thioesterase in maintaining intracellular ROS homeostasis in bacteria and stimulating antibacterial activity.

In the environment, bacteria mainly exist in multicellular, surface-adhered communities called biofilms. One key feature of the biofilms is a self-produced extracellular matrix that embeds cells within a structured community and contributes to their adhesion, organization, and retention. The matrix of most characterized biofilms contains three primary components: polysaccharides, protein, and extracellular DNA (eDNA). Upon biofilm induction, Bacillus subtilis produces and secretes a polysaccharide known as exopolysaccharide (EPS). The 15 genes of the epsA-O operon encode proteins that coordinate the assembly, export, and polymerization of EPS oligosaccharide (glycan) subunits. While much progress has been made to elucidate the chemical structure of EPS, further work is needed to determine the contributions of some eps genes to EPS biosynthesis experimentally. Here, we generated a collection of marker-less, in-frame deletions targeting each eps gene in the epsA-O operon in B. subtilis strain NCIB 3610 using the Cre system. Biofilm phenotypes of resulting mutants were used to assess each gene's importance to biofilm development. Impact The epsA-O single-gene deletion collection was designed to enable systematic assessment of the contribution of each eps gene to EPS production and biofilm-associated phenotypes. When combined with current knowledge of EPS structure, this collection will help clarify the roles of individual genes in EPS biosynthesis. This approach can also be easily adapted for the systematic analyses of other large, complex operons in diverse bacterial species.

Hydrodynamics is a strong regulator of phytoplankton cell densities and population connectivity. However, the extent to which hydrodynamics, specifically dilution and advection, dictates the internal physiological state and overall bloom dynamics remains poorly understood. We conducted an integrated study of the harmful diatom Pseudo-nitzschia australis in two neighboring coastal bays with similar abiotic conditions but contrasting bloom trajectories. Using a combination of field observations, transcriptomics, domoic acid (DA) measurements, and hydrodynamic simulations, we show that a three-fold difference in dilution rates alone explains a 25-day shift in bloom timing and an order-of-magnitude difference in cell densities. Transcriptomic profiling revealed distinct metabolic and stress-associated gene modules that synchronized with hydrodynamically-mediated nutrient depletion rate, linking residence times to cellular mortality. Furthermore, directional connectivity between the bays may explain population-level toxin heterogeneity, as advection of older cells, releasing DA outside the cells, may have decreased the proportion of intracellular DA in the destination bay. Our results illustrate that hydrodynamics do not merely modulate population transport; they structure the full physiological life cycle of a bloom, from initiation to nutrient-driven demise. This highlights the necessity of considering hydrodynamics as a primary explanation for bloom dynamics with cascading effects on bloom onset, cell density, nutrient consumption, cell physiology and mortality.

A native entomopathogenic nematode isolate, Heterorhabditis indica Che4.1, was recovered from soils in Valencia (Spain), and its symbiotic bacterium, Photorhabdus akhurstii Che4.1, was isolated and characterized. Nematode identification was confirmed by ITS and 28S rDNA sequencing, while genome-based analyses supported the taxonomic assignment of the bacterial symbiont. The nematode-bacterium complex exhibited insecticidal activity against Spodoptera exigua and Spodoptera littoralis. H. indica Che4.1 showed an LC of 53.7 infective juveniles (IJs)/mL against S. exigua, comparable to that of the commercial reference Larvanem (54.3 IJs/mL). Against S. littoralis, Che4.1 exhibited an approximately twofold lower LC than Larvanem (77.3 versus 155.9 IJs/mL), with non-overlapping 95% confidence intervals. The complete genome of P. akhurstii Che4.1 consists of a single circular chromosome of 5.66 Mb encoding a diverse repertoire of putative virulence factors, including toxin complex (Tc) components, YenTc-like proteins, Mcf toxins, App-family proteins, Pra/Prb proteins, and chitinases, together with several predicted secondary metabolite biosynthetic gene clusters. LC-MS/MS analyses of bacterial culture supernatants and infected insect cadavers detected multiple predicted virulence-associated proteins, including Tc-related, YenTc-like, App-family, and Pra/Prb proteins. In addition, bacterial cell-free supernatants caused 68.8-81.3% mortality in S. exigua neonates under laboratory conditions. Together, these findings reveal a diverse repertoire of potential virulence determinants in P. akhurstii Che4.1 and demonstrate the insecticidal potential of its native nematodebacterium complex. The performance of H. indica Che4.1 relative to a commercial reference supports further evaluation of this isolate for biological control of Spodoptera spp., particularly under greenhouse and field conditions.

During infection, Klebsiella pneumoniae must withstand host-derived oxidative stress not only by detoxifying reactive oxygen species (ROS) but also by repairing oxidative damage to cellular physiology. How these detoxification and stress-adaptive responses are coordinated remains unclear. Here, we identify a plasmid-encoded tacAT locus as an OxyR-responsive regulatory module that supports peroxide tolerance and in vivo fitness in K. pneumoniae. Guided by the conservation of the OxyR DNA-binding domain and its consensus binding motif, we surveyed promoter-proximal regions of the K. pneumoniae CRK3022 chromosome and plasmids for candidate OxyR-responsive loci. This analysis identified tacAT, a putative type II toxin-antitoxin (TA) module, as the only plasmid-associated candidate. OxyR directly bound the tacAT promoter and contributed to tacAT induction during hydrogen peroxide (H?O?) stress. The TacAT complex exhibited DNA-binding and transcriptional regulatory activity, promoting the expression of genes linked to protein quality control and membrane/envelope homeostasis, including clpB, htpG, cadC, bhsA, and marA. Deletion of tacAT compromised survival under lethal peroxide challenge and attenuated bacterial dissemination, tissue pathology, and inflammatory responses in a murine bacteremia model. These findings define an OxyR-TacAT regulatory branch that connects peroxide sensing with stress-adaptive gene expression, revealing how a TA-associated module can be integrated into stress-adaptive programs during host-associated oxidative stress.

Abstract Background: Soil microbiomes play critical roles in plant health and resilience, yet it is still poorly understood how disruptions in local microbial communities, such as during soil management, impact these ecological functions. In this study, we investigated how compost addition, a widely used soil management practice, and microbiome origin influence microbiome-mediated plant resistance to insects. We combined surveys of working organic farms across New York with controlled laboratory experiments, amplicon sequencing, plant-insect bioassays, and mass spectrometry. Results: Compost use was associated with shifts in the relative abundance of 20 fungal and 2 bacterial genera across ten working farms. However, no consistent changes in bacterial or fungal diversity or community structure in fields with compost were observed across the farms. Under controlled conditions using a common compost source, compost increased rhizosphere microbial diversity and significantly altered rhizosphere community structure, including the relative abundance of 6 fungal and 41 bacterial genera. Despite these substantial community-level changes, compost did not affect populations of green peach aphids (Myzus persicae) on kale (Brassica oleracea). Instead, aphid populations and plant salicylic acid concentrations were more strongly associated with microbiome origin, demonstrating that compost can substantially restructure soil and rhizosphere microbial communities without corresponding changes in microbiome-mediated plant resistance to insects. Conclusions: Our findings demonstrate that microbial diversity and compositional responses to management are not necessarily reliable indicators of all microbiome functions. More broadly, this work highlights the importance of local soil microbiome variation in shaping plant-insect interactions and emphasizes the need to link community-level responses to direct functional measurements when evaluating microbiome responses to agricultural management.

The rapid global expansion of dams has significantly reshaped freshwater ecosystems, yet long-term trophic dynamics and food-web stability within reservoirs remain underexplored. This study examines the reorganization of fish communities induced by the trophic surge following dam construction and river impoundment. We used the predator-to-consumer mass ratio (PCMR) as a proxy for trophic pyramid structure to track changes in fish biomass distribution across three large boreal reservoirs in Quebec, Canada, over 20 years, using data from before and after impoundment. We found transient top-heaviness events (i.e., PCMR values > 1; predator accumulation), characterized by a hump-shaped trajectory of the PCMR values in two reservoirs (Opinaca and Robert Bourassa). The third reservoir (Caniapiscau) showed a gradual increase in top-heaviness but did not exhibit a clear transient pattern. The magnitude and duration of top-heaviness varied across reservoirs, potentially due to differences in the system's capacity to receive and accumulate nutrients, which are driven by water residence time and reservoir size. This research provides a conceptual framework for understanding the long-term trophic dynamics of reservoirs, which can help inform the development of more effective management strategies to preserve ecological health in these ecosystems.

Ecological responses to environmental stressors are increasingly shaped by interactions among anthropogenic and climatic drivers, yet the influence of prior exposure history on subsequent stress responses remains poorly integrated into multiple stressor ecology. Using the blue mussel (Mytilus edulis) as a model system, we experimentally tested whether prior exposure to environmental nanoplastics modifies responses to subsequent stressors, including copper contamination, nutrient enrichment, and salinity fluctuations, individually and in combination. Nanoplastic pre-exposure reduced survival across subsequent treatments and altered stressor interaction outcomes at the community level, shifting responses toward synergistic effects that amplified metabolic costs. These results demonstrate that exposure history can modify both the magnitude and direction of multi-stressor effects, with consequences extending beyond individual performance to ecosystem functioning. By incorporating temporal exposure dynamics into multiple stressor research, our study highlights how ecological responses to global change depend not only on the identity and intensity of stressors, but also on prior environmental conditions shaping subsequent organismal and ecosystem health status and responses.

Extremophilic fungi are a relatively unexplored source of stress-resilient microbes for sustainable agriculture. Here, we describe Talaromyces pseudofuniculosus FAR, isolated from the highly acidic site of Piccolo Inferno in southern Italy and identified by ITS and {beta}-tubulin (BenA) sequencing. Despite its origin from an extreme environment, T. pseudofuniculosus FRA remained fully functional under non-stress conditions and displayed tolerance to salinity and heavy metals while maintaining key plant growth-promoting traits, including phosphate solubilization, auxin-related compound production and hydrolytic activities. In soybean (Glycine max L.), the live fungus promoted plant growth under both non-stress conditions and agriculturally relevant salinity and copper stress, and successfully colonized the roots. A cell-free extracellular extract (exCFS) promoted early seedling development in vitro, but its effects were not sustained in pot experiments. GC-MS analysis provided a qualitative characterization of the extracellular metabolite profile and revealed condition-dependent differences between control, NaCl and CuSO4; growth conditions, indicating environment-dependent modulation of fungal metabolism. Overall, these findings highlight the physiological and metabolic plasticity of T. pseudofuniculosus FRA and support its potential as a fungal biostimulant for saline- and metal-impacted agricultural soils.

Riverine and riparian food webs are connected via 'allochthonous' resource flows from neighboring ecosystems. These resources, such as terrestrial leaf litter, contribute to benthic macroinvertebrate diets, supporting higher trophic levels. While allochthony occurs in streams globally, its sensitivity to broad environmental gradients remains poorly understood. We explored the drivers of allochthony across six river basins within the contiguous United States, including climate, stream size, and flow permanence. We used Bayesian mixing models to estimate macroinvertebrate dietary proportions in four functional feeding groups. Air temperature best predicted allochthony, with consumers relying less on allochthonous resources with increasing temperature. Our models indicate that macroinvertebrate diets become primarily autochthonous at approximately 15{degrees}C mean annual air temperature, with leaf litter-consuming shredders showing a slightly higher threshold for this shift. We also found increased allochthony in smaller, non-perennial streams. These findings highlight the complexity of stream allochthony and responses to multi-scale environmental factors.