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Rhizobacterial communities can contribute to plant trait expression and performance, including plant tolerance against abiotic stresses such as drought. The conditioning of microbial communities related to disease resistance over generations has been shown to develop suppressive soils which aid in plant defense responses. Here, we applied this concept for the development of drought resistant soils. We hypothesized that soils conditioned under severe drought stress and tomato cultivation over two generations, will allow for plant selection of rhizobacterial communities that provide plants with improved drought resistant traits. Surprisingly, the plants treated with a drought-conditioned microbial inoculant showed significantly decreased plant biomass in two generations of growth. Microbial community composition was significantly different between the inoculated and control soils within each generation (i.e., microbial history effect) and for the inoculated soils between generations (i.e., conditioning effect). These findings indicate a substantial effect of conditioning soils on the abiotic stress response and microbial recruitment of tomato plants undergoing drought stress.

Insects are known plant pests, and some of them such as Trichoplusia ni feed on a variety of crops. In this study, Trichoplusia ni was fed distinct diets of leaves of Arabidopsis thaliana or Solanum lycopersicum as well as an artificial diet. After four generations, the microbial composition of the insect gut was evaluated to determine if the diet influenced the structure and function of the microbial communities. The population fed with A. thaliana had higher proportions of Shinella, Terribacillus and Propionibacterium, and these genera are known to have tolerance to glucosinolate activity, which is produced by A. thaliana to deter insects. The population fed with S. lycopersicum expressed increased relative abundances of the Agrobacterium and Rhizobium genera. These microbial members can degrade alkaloids, which are produced by S. lycopersicum. All five of these genera were also present in the respective leaves of either A. thaliana or S. lycopersicum, suggesting that these microbes are acquired by the insects from the diet itself. This study describes a potential mechanism used by generalist insects to become habituated to their available diet based on acquisition of phytochemical degrading gut bacteria.

Sustainable agricultural production requires an inclusive framework that concurrently considers the impacts of production methods on soil health, crop productivity, and crop nutritional quality. However, few studies have directly examined the potential associations among management impacts on soil health (SH), crop productivity, and crop quality. We evaluated these linkages in a continuous maize experiment with treatments varying in nitrogen (N) fertilizer amount and type (zero input control, inorganic N, and manure-based N treatment). We evaluated select SH indicators after six cropping years, and computed physical, chemical, biological, nutrient, and overall SH indices using the Soil Management Assessment Framework (SMAF). Crop yields, mineral nutrient concentrations (denoted with brackets), and nutrient uptake were analyzed in years six and seven. Manure application increased biological SH indicators compared to the control and inorganic N treatments and also increased available potassium (K), zinc (Zn), copper (Cu), and phosphorus (P). Overall SH indices were higher in the inorganic N and manure treatments than in the control but did not differ between the two N sources, despite the large exogenous sources of C, N, and nutrients applied via manure. The SMAF tool only directly considers P and K in terms of soil nutrients—other nutrient benefits of manure application (i.e., increases in total soil N, available Cu and Zn) were not accounted for, suggesting that the SMAF nutrient SH index should be modified to account for the impacts of management practices on nutrient availability. Crop yields were higher in treatments with higher overall SH, supporting the linkages between SH and crop productivity. Despite widely differing nutrient inputs and soil fertility levels, we found no yield differences between the two N sources. However, there were notable treatment impacts on crop quality. Grain [N] was 40% greater in the urea and manure treatments than in the control. Grain [P], [K], and [Mg], important elements in livestock nutrition, were 10% to 28% greater in the manure treatment than in the urea treatment. In addition, although a yield dilution of grain [Zn] occurred in the urea treatment, the dilution effect was mitigated in the manure treatment, likely due to increases in available Zn. Overarchingly, our results suggest that management practices that maintain or improve SH and nutrient availability also improve maize productivity and nutritional quality, which could have cascading positive impacts on animal and human nutrition.

The Carbon Reduction Potential Evaluation (CaRPE) tool is a web-based interactive tool that integrates two databases for the USA collected at county/multi-county scales to visualize and estimate the climate benefits of implementing a variety of conservation practices on croplands and grazing lands. The COMET-Planner tool provides county/multi-county carbon sequestration and greenhouse gas emission reduction coefficients associated with the adoption of climate-smart agricultural management practices. The CaRPE tool couples these coefficients, reported in tonnes of carbon dioxide equivalents (CO2e) per acre per year, with county-level cropland and grazing land acres extracted from the US Agricultural Census. The CaRPE graphical user interface allows users to quickly and easily build and export scenarios of new conservation practice adoption on desired acreages and locations at state, regional or national scales. Results are in tonnes CO2e per year, and each scenario can be exported in tabular and map formats at the selected scales. Existing county-level cropland acreage data provide the upper boundaries for acres of adoption and can be modified based on specific goals established by the user.The output may be used to develop potential targets of adoption and help inform decisions related to resource prioritization and planning efforts. In collaboration with local experts and farmer-led organizations, the results can provide a key starting block to prioritize practices and areas that contribute to climate benefits. As the underlying databases and models are updated and improved, CaRPE can be revised accordingly to increase accuracy and enhance applicability. The CaRPE tool and the user guide are available at: Database URL: https://carpe.shinyapps.io/CarpeTool/

Soil microbiome disruption methods are regularly used to reduce populations of microbial pathogens, often resulting in increased crop growth. However, little is known about the effect of soil microbiome disruption on non-pathogenic members of the soil microbiome. Here, we applied soil microbiome disruption in the form of moist-heat sterilization (autoclaving) to reduce populations of naturally occurring soil microbiota. The disruption was applied to analyze bacterial community rearrangement mediated by four crops (corn, beet, lettuce, and tomato) grown in three historically distinct agroecosystem soils (conventional, organic, and diseased). Applying the soil disruption enhanced plant influence on rhizosphere bacterial colonization, and significantly different bacterial communities were detected between the tested crops. Furthermore, bacterial genera showed significant abundance increases in ways both unique-to and shared-by each tested crop. As an example, corn uniquely promoted abundances of Pseudomonas and Sporocytophaga, regardless of the disrupted soil in which it was grown. Whereas the promotion of Bosea, Dyadobacter and Luteoliobacter was shared by all four crops when grown in disrupted soils. In summary, soil disruption followed by crop introduction amplified the plant colonization of potential beneficial bacterial genera in the rhizosphere.

Root-knot nematodes (RKN) such as Meloidogyne spp. are among the most detrimental pests in agriculture affecting several crops. New methodologies to manage RKN are needed such as efficient discovery of nematophagous microbes. In this study, we developed an in vitro high-throughput method relying on the free-living nematode Caenorhabditis elegans and the infection of those nematodes with a soil slurry containing a microbiome likely to house nematophagous microbes. Nematodes were monitored for presence of infection and sub-cultured repeatedly for the purpose of isolating pure cultures of the microbe responsible for conferring the nematicidal activity. Once soil microbes were confirmed to be antagonistic to C. elegans, they were tested for pathogenicity against Meloidogyne chitwoodi. Using this methodology, the fungal isolate Mortierella globalpina was confirmed to be pathogenic in vitro against M. chitwoodi by nematode trapping via hyphal adhesion to the cuticle layer, penetration of the cuticle layer, and subsequently digestion of its cellular contents. M. globalpina was also observed to reduce disease symptomology of RKNs in vivo via significant reduction of root-galls on tomato (Solanum lycopersicum var. Rutgers).

Soil microbiome disruption methods are regularly used to reduce populations of microbial pathogens, which often results in increase crop growth. However, little is known about the effect of soil microbiome disruption on non-pathogenic members within the soil microbiome. Here, we applied soil microbiome disruption, in the form of moist-heat sterilization (autoclaving) to reduce populations of naturally occurring soil microbiota. The disruption was applied to analyze bacterial community rearrangement mediated by four crops (corn, beet, lettuce, and tomato) grown in three historically distinct agroecosystem soils (conventional, organic, and diseased). Applying the soil disruption enhanced plant influence on bacterial colonization, and significantly different bacterial communities were detected between the tested crops. Furthermore, bacterial genera showed significant abundance increases both unique-to and shared-by each tested crop. As an example, corn uniquely promoted abundances of Pseudomonas and Sporocytophaga, regardless of the disrupted soil in which it was grown. Whereas the promotion of Bosea, Dyadobacter and Luteoliobacter was shared by all crops grown in all disrupted soils. In summary, soil disruption followed by crop introduction amplified plant-mediated selection of plant benefiting bacterial genera.

The following study investigates the timing and mechanism of impact of Swiss needle cast on Douglas-fir (Pseudotsuga menziesii) needle physiology (i.e. gas exchange). Swiss needle cast is a foliar disease caused by the fungus Phaeocryptopus gaeumannii, which occurs throughout the range of Douglas fir and until recently has been considered unimportant. However, recent surveys show the Swiss needle cast currently affects52611 ha of forested lands in western Oregon, USA, causing a reduction in growth of c. 23% or an implied growth loss of c. 3.2 m

Information about the establishment phase of Miscanthus sinensis Andersson as sterile procedure to avoid the contamination were few reported. The aim of this study was to evaluate different immersion sterilization procedures with and without the biocide, Plant Preservative Mixture (PPM?) on in vitro contamination of two Miscanthus genotypes. The plant material were canes from adult plants of two accessions PI 668371 and PI 668375 cultivated in the germplasm bank of USDA-ARS, Griffin, Georgia. Apical meristems were submitted to immersion sterilization procedures (70% isopropyl alcohol and 1.5, 5.0 or 8.25% NaOCl for different time periods, followed by rinsing three times with autoclaved distilled water. After that, the explants were inoculated on MS basal medium in the presence or absence of 1 mL L-1 PPM?. The experimental design was fully randomized in a 2 x 5 x 2 factorial scheme (genotypes x sterilization process x PPM?) with five replicates per treatment and five apical meristems per experimental unit. Aseptic treatments showed no differences for percentage of bacterial and fungal contaminations and percentage of explant survival. In the presence of PPM ? there was less bacterial contamination in the accessions (28%) than in the absence (100%). For the percentage of fungal contamination, PPM ? had no significant effect on PI 668371 accession. However, on PI 668375 accession there was a lower percentage of fungal contamination (16%). The biocide PPM ? may be an efficient agent to prevent bacterial contamination on in vitro cultures of Miscanthus spp and fungal contamination in PI 668375 accession. Made available in DSpace on 2020-12-23T09:04:29Z (GMT). No. of bitstreams: 1 16.-Ana-Ledo-Sterilization-procedures-and-plant.pdf: 541048 bytes, checksum: 0a107e45b3f2de53cb2e54dcde5369ac (MD5) Previous issue date: 2019

Thatch management in turfgrass has been recommended as part of integrated pest management; however, there is limited understanding of the microbial community in thatch. Previous studies on the turfgrass phytobiome mostly focused on the soil; however, culture-based studies have suggested that the thatch layer of golf courses contains higher bacterial and fungal abundances than the soil. In our study, quantitative PCR was used to investigate total abundance of bacteria, fungi, and the turfgrass pathogen, Sclerotinia homoeocarpa (causal agent of dollar spot) in the thatch and soil of three golf courses on two sampling dates. Additionally, we compared the abundance of these organisms among roughs, fairways, and putting greens, which are under different management intensities. Our results demonstrate bacterial abundance was higher in May than in September, but not consistently higher in the thatch or soil among the three golf courses or management areas. Fungi, and specifically S. homoeocarpa, are more abundant in the thatch than in the soil. These results show the necessity for future turfgrass phytobiome studies to analyze both thatch and soil to obtain a complete picture of bacterial and fungal microbial community structure and dynamics on golf courses. Despite the differences in fungicide usage and management inputs, there were no differences in S. homoeocarpa abundance among the three management areas in the soil. S. homoeocarpa abundance was higher in the thatch on the conventional golf course fairway in September. These results may have important practical implications for development of integrated disease management strategies and for understanding the epidemiology of S. homoeocarpa on golf courses.

Soils are the keystone of healthy and vibrant ecosystems, providing physical, chemical, and biological substrates and functions necessary to support life. In particular, it's the extensive and elaborate matrix of soil microorganisms and other life forms that contributes to soil health and utility. But soils are under constant threat from heavy use, changing climate, and in some cases poor management (1, 2). In view of soil’s key role and threatened status, we believe that there is a need for the scientific community to undertake coordinated research and development efforts that will lead to a unique asset: a National Living Soil Repository (Fig. 1). Fig. 1. A National Living Soil Repository would store agricultural cryogenic and air-dried soil samples, analyze samples for microbial community composition, assess samples for microbial viability, and serve as a potential source of living organisms for various agricultural ecosystem services. Image courtesy of Jennifer Moore-Kucera (USDA Natural Resources Conservation Service) and Daniel Manter (USDA Agricultural Research Service). Already local and national soil archives have been shown to be of great utility for studying, analyzing, and documenting long-term environmental and ecological trends. For example, the historical soil archive at Hubbard Brook helped researchers discover the link between fossil fuels and acidification of rain and snow (3); the Rothamsted Sample Archive in the United Kingdom has shown a steady increase in dioxins during the last century (4). And yet, a soil repository/archive designed to preserve native biological diversity does not currently exist. Such an archive would provide the ability to acquire data on the current biological (e.g., soil health) state of soils around the country across soil types, cropping systems, and ecosystems and over time. Further, by maintaining soil archives and a catalog of their microbial communities, we will gain a better understanding of how soil organisms are distributed … [↵][1]1To whom correspondence should be addressed. Email: Jorge.Delgado{at}ars.usda.gov. [1]: #xref-corresp-1-1

Nematodes are an important component of the golf course ecosystem. Many species provide benefits to turfgrass, while others can cause significant damage. Previous studies on golf courses have focused only on herbivore nematodes, mostly on putting greens. This study aimed to characterize all nematode trophic groups and nematode maturity and ecological indices under different management intensities (depicted by roughs, fairways, and putting greens) of three golf courses representing conventional and organic management types over two seasons in 2013 and 2014. The putting greens on all three golf courses had lower diversity and herbivore (plant-parasitic) index (PPI) values than the other management areas. The relative abundance of herbivores, bacterivores, and structure index (SI) values differed among organic and conventional management. Canonical correspondence and multiple stepwise regression analyses revealed pH, phosphorous, and organic matter were positively related to increased herbivores and negatively related to increased bacterivores. The results of this study can be used to develop alternative management practices aimed at decreasing problematic herbivore populations on putting greens and increasing potentially beneficial bacterivores.

Pratylenchus neglectus and Meloidogyne chitwoodi are the main plant-parasitic nematodes in potato crops of the San Luis Valley, Colorado. Bacterial microbiome (16S rRNA copies per gram of soil) and nematode communities (nematodes per 200 g of soil) from five different potato farms were analyzed to determine negative and positive correlations between any bacterial genus and P. neglectus and M. chitwoodi. Farms showed differences in bacterial communities, percentage of bacterivorous and fungivorous nematodes, and numbers of P. neglectus and M. chitwoodi. The farm with the lowest population of P. neglectus and M. chitwoodi had higher abundances of the bacterial genera Bacillus spp., Arthrobacter spp., and Lysobacter spp., and the soil nematode community was composed of more than 30% of fungivorous nematodes. In contrast, the farm with higher numbers of P. neglectus and M. chitwoodi had a lower abundance of the abovementioned bacterial genera, higher abundance of Burkholderia spp., and less than 25% of fungivorous nematodes. The α-Proteobacteria Rhodoplanes, Phenylobacterium, and Kaistobacter positively correlated with M. chitwoodi, and the Bacteroidia and γ-Proteobacteria positively correlated with P. neglectus. Our results, based largely on co-occurrence analyses, suggest that the abundance of Bacillus spp., Arthrobacter spp., and Lysobacter spp. in Colorado potato soils is negatively correlated with P. neglectus and M. chitwoodi abundance. Further studies will isolate and identify bacterial strains of these genera, and evaluate their nematode-antagonistic activity.

The dynamics of microbial communities associated with dying cover crops are of interest because of potential impacts on disease in a subsequent crop, and because of the importance of microbial activity on plant residue to soil organic matter dynamics and nutrient cycling. We used high throughput amplicon sequencing to characterize the composition and structure of oomycete and fungal communities associated with a rye cover crop, and to track their community dynamics in the first several weeks after herbicide was applied to terminate the cover crop. The dominant oomycetes associated with cereal rye roots were Pythium volutum, Pythium sp. F86 (an unknown species within clade B), and Lagena radicicola. Because P. volutum is sensitive to common additives in isolation media, and L. radicicola is an obligate intracellular parasite, a unique aspect of this work is to reveal the dominance of oomycete taxa that would have been missed entirely under a traditional cultivation-based approach. Based on first detection in an amplicon sequencing survey, we were able to isolate P. volutum and Pythium sp. F86. We demonstrate that both species are pathogenic on corn, and that corn seedlings grown in the field following a rye cover crop show elevated rates of infection by P. volutum, highlighting a potential disease risk associated with cover cropping. P. volutum and Pythium sp. F86 exhibited contrasting spatial patterns of abundance, with nearly complete turnover of the dominant species across the field site. In contrast to the strong spatial structuring and low diversity of oomycete communities, fungal communities associated with a cereal rye cover crop were more diverse and dynamic, with some displacement of basidiomycetes by ascomycetes over time. Several plant pathogens, as well as putative beneficial organisms, were detected among fungal communities associated with rye roots. This work sheds light on microbial community dynamics on dying host plants, highlights the power of culture-independent microbial community assessment to yield new insights, and suggests the need for informed management to reduce seedling disease risk in corn following rye cover crops.

Estrogen decline during menopause is associated with altered metabolism, weight gain and increased risk of cardiometabolic diseases. The gut microbiota also plays a role in the development of cardiometabolic dysfunction and is also subject to changes associated with age-related hormone changes. Phytoestrogens are plant-based estrogen mimics that have gained popularity as dietary supplements for the treatment or prevention of menopause-related symptoms. These compounds have the potential to both modulate and be metabolized by the gut microbiota. Hops (Humulus lupulus L.) contain potent phytoestrogen precursors, which rely on microbial biotransformation in the gut to estrogenic forms. We supplemented ovariectomized (OVX) or sham-operated (SHAM) C57BL/6 mice, with oral estradiol (E2), a flavonoid-rich extract from hops, or a placebo carrier oil, to observe effects on adiposity, inflammation, and gut bacteria composition. Hops extract (HE) and E2 protected against increased visceral adiposity and liver triglyceride accumulation in OVX animals. Surprisingly, we found no evidence of OVX having a significant impact on the overall gut bacterial community structure. We did find differences in the abundance of Akkermansia muciniphila, which was lower with HE treatment in the SHAM group relative to OVX E2 treatment and to placebo in the SHAM group.

Estrogen decline during menopause is associated with altered metabolism, weight gain and increased risk of cardiometabolic diseases. The gut microbiota also plays a role in the development of cardiometabolic dysfunction and is also subject to changes associated with age-related hormone changes. Phytoestrogens are plant-based estrogen mimics that have gained popularity as dietary supplements for the treatment or prevention of menopause-related symptoms. These compounds have the potential to both modulate and be metabolized by the gut microbiota. Hops (Humulus lupulus L.) contain potent phytoestrogen precursors, which rely on microbial biotransformation in the gut to estrogenic forms. We supplemented ovariectomized (OVX) or sham-operated (SHAM) C57BL/6 mice, with oral estradiol (E2), a flavonoid-rich extract from hops, or a placebo carrier oil, to observe effects on adiposity, inflammation, and gut bacteria composition. Hops extract (HE) and E2 protected against increased visceral adiposity and liver triglyceride accumulation in OVX animals. Surprisingly, we found no evidence of OVX having a significant impact on the overall gut bacterial community structure. We did find differences in the abundance of Akkermansia muciniphila, which was lower with HE treatment in the SHAM group relative to OVX E2 treatment and to placebo in the SHAM group.

There is evidence that shows that phosphorus (P) fertilization has a moderate effect on the rhizosphere microbial composition of cultivated crops. But how this effect is manifested on wild species of the same crop is not clear. This study compares the impact of phosphorus fertilization with rhizosphere bacterial community composition and its predicted functions, related to P-cycling genes, in both cultivated and non-cultivated potato (Solanum sp.) plants. It was found that the biomass of non-cultivated potatoes was more responsive to P fertilization as compared with cultivated plants. Differences in general bacterial community composition patterns under increasing P amendments were subtle for both potato groups. However, potato genotype significantly influenced community composition with several bacterial families being more abundant in the cultivated plants. In addition, the predicted phosphatases had lower abundances in modern cultivars compared with non-cultivated potatoes. In summary, despite higher accumulation of differentially abundant bacteria in the rhizosphere of cultivated plants, the responsiveness of these plants to increase P levels was lower than in non-cultivated plants.

The gut microbiota is increasingly recognized as an important modulator of human health. As such, there is a growing need to identify effective means of selectively modifying gut microbial communities. Bacteriophages, which were briefly utilized as clinical antimicrobials in the early 20th century, present an opportunity to selectively reduce populations of undesirable microorganisms. However, whether intentional consumption of specific bacteriophages affects overall gut ecology is not yet known. Using a commercial cocktail of Escherichia coli-targeting bacteriophages, we examined their effects on gut microbiota and markers of intestinal and systemic inflammation in a healthy human population. In a double-blinded, placebo-controlled crossover trial, normal to overweight adults consumed bacteriophages for 28 days. Stool and blood samples were collected and used to examine inflammatory markers, lipid metabolism, and gut microbiota. Reductions in fecal E. coli loads were observed with phage consumption. However, there were no significant changes to alpha and beta diversity parameters, suggesting that consumed phages did not globally disrupt the microbiota. However, specific populations were altered in response to treatment, including increases in members of the butyrate-producing genera Eubacterium and a decreased proportion of taxa most closely related to Clostridium perfringens. Short-chain fatty acid production, inflammatory markers, and lipid metabolism were largely unaltered, but there was a small but significant decrease in circulating interleukin-4 (Il-4). Together, these data demonstrate the potential of bacteriophages to selectively reduce target organisms without global disruption of the gut community.

Organic farming is frequently touted as being beneficial to soil health by increasing microbial community diversity; however, contradictory results exist in the literature. In this study, we compared several organic and conventional potato farms in Colorado for differences in soil nutrients and microbial communities using 454 pyrosequencing of the 18S ribosomal RNA gene. Organic farms showed a slightly higher diversity and evenness within the microbial community compared with conventional farms. No difference in the number of observed or estimated total operational taxonomic units (OTUs) was observed between management strategies. However, the relative abundance of 16 OTUs (3% genetic distance) differed between the organic and conventional farms, with seven increasing and nine decreasing in organic farms. A variety of known potato fungal pathogens (e.g., Alternaria spp., Ulocladium spp., and Pythium ultimum) were detected in the soil, including three different OTUs (3% genetic distance) with a high homology to the early blight pathogen Alternaria solani. Relative abundance for Alternaria spp. was higher in conventional farms (relative abundance 30.15 versus 7.8%), whereas the relative abundance for P. ultimum was higher in organic farms (relative abundance 0.25 versus 0.05%). Quantitative polymerase chain reaction, using primers specific for A. solani, Phoma foveata, and Pythium ultimum, yielded similar results to the pyrosequencing, validating the use of pyrosequencing data for the quantification of OTU relative abundances.

The composition and function of microbial communities in the rhizosphere of crops have been linked to edaphic factors and root exudate composition. We examined the effect of N fertilizer (urea) rate on maize root exudation, the associated rhizosphere microbial community, and nitrogen-use-efficiency. Increasing N rate had a significant effect on root exudate quantity and composition. Specifically, the total abundance of sugars, sugar alcohols, and phenolics was positively correlated with N rate (p 0.05). However, on a total abundance basis (gene copies g−1 soil FW) all N-cycle genes increased significantly with increasing N rate (p

Edible insects are often considered a nutritious, protein-rich, environmentally sustainable alternative to traditional livestock with growing popularity among North American consumers. While the nutrient composition of several insects is characterized, all potential health impacts have not been evaluated. In addition to high protein levels, crickets contain chitin and other fibers that may influence gut health. In this study, we evaluated the effects of consuming 25 grams/day whole cricket powder on gut microbiota composition, while assessing safety and tolerability. Twenty healthy adults participated in this six-week, double-blind, crossover dietary intervention. Participants were randomized into two study arms and consumed either cricket-containing or control breakfast foods for 14 days, followed by a washout period and assignment to the opposite treatment. Blood and stool samples were collected at baseline and after each treatment period to assess liver function and microbiota changes. Results demonstrate cricket consumption is tolerable and non-toxic at the studied dose. Cricket powder supported growth of the probiotic bacterium, Bifidobacterium animalis, which increased 5.7-fold. Cricket consumption was also associated with reduced plasma TNF-α. These data suggest that eating crickets may improve gut health and reduce systemic inflammation; however, more research is needed to understand these effects and underlying mechanisms.

Aims The aim of this study was to evaluate effects of PGPR (plant growth-promoting rhizobacteria) isolated from rainforest soil on different plants under limited nitrogen conditions. Methods and Results Bacterial isolates from a Peruvian rainforest soil were screened for plant growth-promoting effects on Arabidopsis (Col-0). Four selected isolates including one Bacillus subtilis, two B. atrophaeus and one B. pumilus significantly promoted growth of Zea mays L. and Solanum lycopersicum under greenhouse conditions. Moreover, the PGPRs significantly promoted growth of S. lycopersicum in both low and nitrogen-amended soil conditions. These PGPR strains were further studied to obtain insights into possible mechanisms of plant growth promotion. Volatile chemicals from those isolates promoted Arabidopsis growth, and the expression of genes related to IAA production was induced in the Arabidopsis plants treated with PGPRs. Further, selected PGPR strains triggered induced systemic resistance (ISR) against Pseudomonas syringae pv tomato DC3000 in Arabidopsis. Conclusions PGPR strains isolated from the rainforest soil promoted the plant growth of Arabidopsis, corn and tomato. Significance and Impact of the Study New PGPR that have wider adaptability to different crops, soils and environmental conditions are needed to decrease our reliance on agricultural amendments derived from fossil-based fuels. The PGPRs isolated from a nonagricultural site constitute new plant growth-promoting strains that could be developed for agricultural uses.

hat is a resilient, healthy soil? A resilient soil is capable of recovering from or adapt-ing to stress, and the health of the living/biological component of the soil is cru-cial for soil resiliency. Soil health is tightly coupled with the concept of soil quality (table 1), and the terms are frequently used interchangeably. The living component of soil or soil biota represents a small fraction (

Estrogen decline during menopause is associated with altered metabolism, weight gain and increased risk of cardiometabolic diseases. The gut microbiota also plays a role in the development of cardiometabolic dysfunction and is also subject to changes associated with age-related hormone changes. Phytoestrogens are plant-based estrogen mimics that have gained popularity as dietary supplements for the treatment or prevention of menopause-related symptoms. These compounds have the potential to both modulate and be metabolized by the gut microbiota. Hops (Humulus lupulus L.) contain potent phytoestrogen precursors, which rely on microbial biotransformation in the gut to estrogenic forms. We supplemented ovariectomized (OVX) or sham-operated (SHAM) C57BL/6 mice, with oral estradiol (E2), a flavonoid-rich extract from hops, or a placebo carrier oil, to observe effects on adiposity, inflammation, and gut bacteria composition. Hops extract (HE) and E2 protected against increased visceral adiposity and liver triglyceride accumulation in OVX animals. Surprisingly, we found no evidence of OVX having a significant impact on the overall gut bacterial community structure. We did find differences in the abundance of Akkermansia muciniphila, which was lower with HE treatment in the SHAM group relative to OVX E2 treatment and to placebo in the SHAM group.

Drought is a major constraint on agricultural production. Crop genetic improvement for drought tolerance has received much attention and there is ample information about the ability of specific soil microbes to influence drought tolerance in plants. However, in nature, plants interact simultaneously with an array of beneficial, benign and pathogenic microbes. There is a need to understand the cumulative effect of these multiple interactions on a plant's ability to overcome abiotic stresses such as drought. The objective of this research was to investigate the potential of whole soil microbiomes to help Arabidopsis thaliana plants deal with drought stress under in vivo conditions. A sympatric microbiome (i.e., having a history of exposure to Arabidopsis at a natural site) significantly increased plant biomass under drought conditions, but caused earlier death rates as a consequence of drought; whereas, the two non-sympatric soils did not influence Arabidopsis biomass. Consistent with this, we observed reduced expression levels for several Arabidopsis drought response marker genes (ATDI21, DREB1A, DREB2A, and NCED3) in the sympatric Arabidopsis soil treatment. Pyrosequencing analysis of the three soil microbiomes used in this study identified 84 bacterial OTUs (3% genetic distance) from 41 genera (Burkholderia, Phormidium, Bacillus, Aminobacter, Acidiphilum and among others) that were significantly higher in the sympatric Arabidopsis soil, as compared to the two non-sympatric soils. In conclusion, we have identified a robust set of Arabidopsis-associated microbes that when present in the soil can modify the plant's ability to sense abiotic stress and increase its biomass production.

Ethanol in sapwood was analyzed along vertical transects, through small spot cankers and larger basal cankers, of Phytophthora ramorum-infected stems of Quercus agrifolia at three sites in California. Trees with large basal cankers, known to attract scolytid beetles, had a 4.3 times higher ethanol level than trees with spot cankers that attract fewer beetles. Ethanol concentrations inside cankers, where scolytid beetles preferentially attack, varied by about four orders of magnitude among samples, with a median level of 16.0 μg.g(-1) fresh mass. This concentration was 4.3 and 15.5 times greater, respectively, than the concentrations at 1 cm or 15-30 cm outside the canker boundaries. In the laboratory, we demonstrated that ethanol escaped through the bark of a Q. garryana log just 3 days after it was added to the sapwood. At the three study sites, traps baited with ethanol captured more Xyleborinus saxesenii, Pseudopityophthorus pubipennis, and Monarthrum dentiger (all Coleoptera: Curculionidae: Scolytinae) than traps baited with ethanol plus (-)-α-pinene, or ethanol plus 4-allylanisole (4AA). Logs of Q. agrifolia with a 50 % ethanol solution added to the sapwood were placed at the study sites, with or without additional bark treatments above the ethanol. The number of scolytid beetle gallery holes above the ethanol-infused sapwood was 4.4 times greater than that on the opposite side of the log where no ethanol was added. Attachment of ultra-high release (-)-α-pinene pouches to the bark surface above the 50 % ethanol solution reduced scolytid attacks to a density of 19.1 % that of logs without this treatment. We conclude that ethanol in P. ramorum cankers functions as a primary host attractant for scolytid beetles and is an important link in colonization of these cankers and accelerated mortality of Q. agrifolia. The results of this research shed light on the chemical ecology behind the focused scolytid attacks on P. ramorum-infected coast live oaks, and lay the groundwork for future efforts to prolong the survival of individual trees of this keystone species.

The need to enhance the sustainability of intensive agricultural systems is widely recognized One promising approach is to encourage beneficial services provided by soil microorganisms to decrease the inputs of fertilizers and pesticides. However, limited success of this approach in field applications raises questions as to how this might be best accomplished. We highlight connections between root exudates and the rhizosphere microbiome, and discuss the possibility of using plant exudation characteristics to selectively enhance beneficial microbial activities and microbiome characteristics. Gaps in our understanding and areas of research that are vital to our ability to more fully exploit the soil microbiome for agroecosystem productivity and sustainability are also discussed. This article outlines strategies for more effectively exploiting beneficial microbial services on agricultural systems, and cals attention to topics that require additional research.

A variety of soil factors are known to increase nutrient availability and plant productivity. The most influential might be the organisms comprising the soil microbial community of the rhizosphere, which is the soil surrounding the roots of plants where complex interactions occur between the roots, soil, and microorganisms. Root exudates act as substrates and signaling molecules for microbes creating a complex and interwoven relationship between plants and the microbiome. While individual microorganisms such as endophytes, symbionts, pathogens, and plant growth promoting rhizobacteria are increasingly featured in the literature, the larger community of soil microorganisms, or soil microbiome, may have more far-reaching effects. Each microorganism functions in coordination with the overall soil microbiome to influence plant health and crop productivity. Increasing evidence indicates that plants can shape the soil microbiome through the secretion of root exudates. The molecular communication fluctuates according to the plant development stage, proximity to neighboring species, management techniques, and many other factors. This review seeks to summarize the current knowledge on this topic.