Microbial Amendments Research Articles

Biocontrol agent amendments shape the soybean rhizosphere in a cyst nematode (Heterodera glycines) conducive soil over a two-year field trial

Plant-associated beneficial microorganisms play a vital role in promoting plant health, fitness, and disease suppression, leading to improved plant growth and protection against specific plant parasites. Microbial amendments may reduce nematode parasite populations and ensure plant yield, yet their long-term impact on the native plant microbiome under field conditions is not well understood. In this study, we evaluated the effectiveness of biocontrol products against soybean cyst nematode (SCN) using two application methods over a two-year period under field conditions. Pochonia chlamydosporia PC10 (Rizotec), Bacillus methylotrophicus UFPEDA 20 (Onix), and Trichoderma koningiopsis GF 362 were applied either through seed inoculation or in-furrow treatment at planting. The treatments effectively reduced the nematode population, with T. koningiopsis showing significant deviations from the control and leading to a notable increase in yield. No difference in the Shannon diversity index was detected for the alpha-diversity of root-associated 16S, ITS2, and 18S communities. The dominant phyla were Proteobacteria, Acidobacteria, Actinobacteria for 16S; Ascomycota, Basidiomycota, Mortierellomycota for ITS2; and Ascomycota, and Cercozoa for 18S. In the 16S community, T. koningiopsis and B. methylotrophicus caused a 25 % increase in the relative abundance of Sphingomonas spp. compared to the control. Additionally, the relative abundance of Mortierella spp. significantly increased by 50 % in both the T. koningiopsis and B. methylotrophicus treatments compared to the control. Both treatments also led to a significant reduction in Fusarium spp. by 37.5 % and 31.5 %, respectively. Co-occurrence network analysis revealed that communities were disrupted after the first application, but grew more intricate and cohesive after the second year of biocontrol product amendment. T. koningiopsis and B. methylotrophicus demonstrated potential in reducing nematode and Fusarium populations, leading to increased yield production. However, under high nematode pressure, relying solely on biocontrol measures does not guarantee a reduction in SCN population or yield improvement. Manipulating the microbial community to reduce harmful organisms and promote biocontrol-related species may offer long-term benefits.

Soil amendments alter cadmium distribution and bacterial community structure in paddy soils

Soil amendments play a pivotal role in ensuring the safety of food production by inhibiting the transfer of heavy metal ions from soils to crops. Nevertheless, their impact on soil characteristics and the microbial community and their role in reducing cadmium (Cd) accumulation in rice remain unclear. In this study, pot experiments were conducted to investigate the effects of three soil amendments (mineral, organic, and microbial) on the distribution of Cd speciation, organic components, iron oxides, and microbial community structure. The application of soil amendments resulted in significant reductions in the soil available Cd content (16 %–51 %) and brown rice Cd content (16 %–78 %), facilitating the transformation of Cd from unstable forms (decreasing 10 %–20 %) to stable forms (increasing 77 %–150 %) in the soil. The mineral and organic amendments increased the soil cation exchange capacity (CEC) and plant-derived organic carbon (OC), respectively, leading to reduced Cd accumulation in brown rice, while the microbial amendment enhanced OC complexity and the abundances of Firmicutes and Bacteroidota, contributing to the decreased rice Cd uptake. The synchrotron radiation–based Fourier transform infrared (SR-FTIR) spectroscopy indicated that soil amendments regulated soil Cd species by promoting iron oxides and OC coupling. Moreover, both organic and microbial amendments significantly reduced the diversity and richness of the bacterial communities and altered their compositions and structures, by increasing the relative abundances of Bacteroidota and Firmicutes and decreasing those of Acidobacteria, Actinobacteria, and Myxococcota. Soil microbiome analysis revealed that the increase of Firmicutes and Bacteroidota associated with Cd adsorption and sequestration contributed to the suppression of soil Cd reactivity. These findings offer valuable insights into the potential mechanisms by which soil amendments regulate the speciation and bioavailability of Cd, and improve the bacterial communities, thereby providing guidance for agricultural management practices.

Ammonia and greenhouse gas emissions from beef feedlot surface material treated with aluminum sulfate (alum) or microbial amendments.

A lab-scale study evaluated ammonia (NH3 ) and greenhouse gases, emissions when aluminum sulfate (alum) or a microbial product were added to beef feedlot surface material (FSM). Three kilograms of FSM and 1.5kg of water were added to stainless steel pans (50cm × 30cm × 6.5cm). Treatments included a control (no amendment), 450g alum, or 0.5g microbial product. The pans were placed in an environmental chamber that was maintained at 23°C and 50%-60% humidity. Emissions were measured three times weekly for 3 weeks. Ammonia, N2 O, and CH4 were lower (p<0.01) from pans with amendments compared to the control pans; emissions from the FSM that received the microbial treatment were lower than the FSM treated with alum. Methane emissions were similar for the control and alum-treated FSM but lower (p<0.01) for the FSM that was treated with the microbial product. Nitrate-N was lower, and NH4+ -N and total sulfur concentrations were higher in FSM treated with alum compared to no treatment or the microbial treatment (p<0.01). Results indicate that both alum and microbial amendments have benefits in reducing emissions from the feedlot surface, with the microbial product providing additional reductions in emissions compared to the alum.

Phyllosphere microbial associations improve plant reproductive success.

The above-ground (phyllosphere) plant microbiome is increasingly recognized as an important component of plant health. We hypothesized that phyllosphere bacterial recruitment may be disrupted in a greenhouse setting, and that adding a bacterial amendment would therefore benefit the health and growth of host plants. Using a newly developed synthetic phyllosphere bacterial microbiome for tomato (Solanum lycopersicum), we tested this hypothesis across multiple trials by manipulating microbial inoculation of leaves and measuring subsequent plant growth and reproductive success, comparing results from plants grown in both greenhouse and field settings. We confirmed that greenhouse-grown plants have a relatively depauperate phyllosphere bacterial microbiome, which both makes them an ideal system for testing the impact of phyllosphere communities on plant health and important targets for microbial amendments as we move towards increased agricultural sustainability. We find that the addition of the synthetic microbial community early in greenhouse growth leads to an increase in fruit production in this setting, implicating the phyllosphere microbiome as a key component of plant fitness and emphasizing the role that these bacterial microbiomes likely play in the ecology and evolution of plant communities.

Effect of organic and microbial amendments on the soil structure and properties of eroded Epicalcic Chernozem from northern Bulgaria

Effect of organic and microbial amendments on the soil structure and properties of eroded Epicalcic Chernozem from northern Bulgaria

Effect and Application of Different Amendments on Salinized Soil Remediation

At present, China's saline-alkali soil area is very large. In the saline-alkali soil, the salinity will affect the growth of plants in the severe areas, so the plants cannot survive. How to maintain soil quality and prevent soil salt from being high has become an important research goal of soil improvement. Soil amendments can combine many small soil particles together to form large water stable aggregates. And it is widely used to prevent soil erosion, reduce soil water evaporation or excessive evaporation, save the amount of irrigation and promote the healthy growth of plants. This study through the use of homemade iron han ecological amendments, phosphogypsum, garden waste decay secondary materials, five materials mixed polyacrylamide and microbial amendments, combined with the water salt engineering comparison experiment, the whole experiment for three, respectively is composite amendments and water salt engineering comprehensive improvement measures (TG1, TG2), the traditional composite amendments (G 1, G 2) and tai tian shallow water conservancy salt project (T) single measures. In the above experiments, the best effects are TG 1 (comprehensive improvement measures of Tiehan ecological amendments) and TG 2 (comprehensive improvement measures of Heka amendments). Although the amount of reagent applied is different, the treatment effect is very good. The results show that different improvement measures significantly reduced the salt content and reduced the PH value of soil, and improved the soil nutrients. This measurement data provides a certain theoretical basis for the repair and study of salinized soil. It also shows that soil amendments have obvious guidance for the application of salinized soil.

Synthetic bacterial communities reshape microbial communities and enhance nutrient supply in desertified land of Northwest China

Climate change and human disturbance have led to widespread soil degradation worldwide. The problem of desertification is gradually destroying soil carbon accumulation. Synthetic bacterial communities (SynComs) are a healthy solution capable of improving the microbiome for plant growth. However, the effect of SynCom on nutrient functions in desertified land remains poorly understood. Here, two years of different treatments (control, chemical fertilizer, SynCom, combined SynCom-Chemical fertilizer) were conducted on desertified land in the Loess Plateau, and we aimed to reveal the effects of introducing SynCom on bacterial communities and nutrient multifunctionality. The SynCom enriched more beneficial bacteria as key microorganisms and increased biodiversity. At the same time, the bacterial community structure of the desertified land shifted significantly and remained stable at the soil surface (0–10 cm). We found that SynCom enhanced the complexity of the bacterial network with higher modularity. Our results also revealed the influence of biotic and abiotic factors on nutrient availability. Bacterial diversity and soil electrical conductivity (EC) were the significant influencing factors for chemical and combined fertilizers. However, SynCom exhibited stronger bacterial effects, and soil organic matter significantly affected the biodiversity-ecosystem function (BEF) relationships. Overall, this study illustrates the impact of microbial amendment on nutrient function in desertified land and provides insights into SynCom application to enhance ecosystem restoration and carbon sinks.

Assessing the efficacy of extruded seed pellets and microbial amendments for native revegetation

Worldwide, there is a strong need for new, innovative, large‐scale approaches to restoring diverse native vegetation. Seed‐based revegetation, while often employed, can suffer from low plant establishment. Various seed coating technologies have been widely employed for decades to promote efficient agricultural planting; however, a significant obstacle to the implementation of this technology for native species revegetation is the limited access to the expertise and techniques which are mostly confidential to and specialized for the agrochemical industry. Here we investigated whether the seeds of Australian native species may benefit from extruded pelleting, measuring both seedling emergence and early growth, and testing the pellets with and without the addition of a commercial plant probiotic. A manipulative glasshouse experiment was carried out with three treatments (bare seeded; standard pellets; pellets amended with a probiotic) for four native plant species. Incorporation of seeds within standard pellets was shown to maintain high percentages of emergence and improve growth of three of the tested species (Daviesia ulicifolia, Hardenbergia violacea, and Indigofera australis) in the glasshouse setting, with increases in mean biomass of 83, 385, and 1,002%, respectively. However, emergence in the fourth species (Bursaria spinosa) was low in all seed treatments, perhaps due to excessive sowing depth (bare seeds), while combined with being encased inside a pellet. Relative to the standard pellets, probiotic amended pellets did not impart further detectable emergence or growth benefits. Ultimately, these results highlight exciting prospects for the application of extruded seed pellets in facilitating efficient use of seed in the revegetation of some native species.

Characterizing Effects of Microbial Biostimulants and Whole-Soil Inoculums for Native Plant Revegetation

Soil microbes play important roles in plant health and ecosystem functioning, however, they can often be disturbed or depleted in degraded lands. During seed-based revegetation of such sites there is often very low germination and seedling establishment success, with recruitment of beneficial microbes to the rhizosphere one potential contributor to this problem. Here we investigated whether Australian native plant species may benefit from planting seed encapsulated within extruded seed pellets amended with one of two microbe-rich products: a commercial vermicast extract biostimulant or a whole-soil inoculum from a healthy reference site of native vegetation. Two manipulative glasshouse trials assessing the performance of two Australian native plant species (Acacia parramattensis and Indigofera australis) were carried out in both unmodified field-collected soil (trial 1) and in the same soil reduced in nutrients and microbes (trial 2). Seedling emergence and growth were compared between pelleted and bare-seeded controls and analyzed alongside soil nutrient concentrations and culturable microbial community assessments. The addition of microbial amendments maintained, but did not improve upon, high levels of emergence in both plant species relative to unamended pellets. In trial 1, mean time to emergence of Acacia parramattensis seedlings was slightly shorter in both amended pellet types relative to the standard pellets, and in trial 2, whole-soil inoculum pellets showed significantly improved growth metrics. This work shows that there is potential for microbial amendments to positively affect native plant emergence and growth, however exact effects are dependent on the type of amendment, the plant species, and the characteristics of the planting site soil.

Management‐induced shifts in rhizosphere bacterial communities contribute to the control of pathogen causing citrus greening disease

AbstractIntroductionCitrus greening (aka Huanglongbing, HLB) caused primarily by the bacterial pathogen Candidatus Liberibacter asiaticus (CLas) has devastating effects on the global citrus industry. Agricultural management‐induced changes in microbial communities are hypothesised to contribute toward HLB resistance by reducing pathogen titre and increasing root and soil health. However, we have a limited understanding of the impacts of management practices on the soil microbiome, making the extent of HLB management uncertain.Material and MethodsHere we investigated the effect of agricultural management practices on reducing CLas titer via changes in rhizosphere‐associated bacterial communities. Rhizosphere and root samples were collected from two sites in Florida where different management practices (e.g., metalized reflective mulch ground covers, compost application and microbial inoculations) are currently being implemented to prevent HLB. Management‐induced changes in the rhizosphere bacterial community were assessed using amplicon sequencing. qPCR assays were used to quantify the titer of the pathogen CLas in roots. In addition, we measured soil properties and the activities of microbial enzymes involved in soil nutrient cycling.ResultsOur results indicated that certain management practices lead to shifts in the community structure of rhizosphere bacterial communities that negatively interact with the HLB pathogen. Management practices improved soil quality and reduced CLas titer. Additionally, we found that Actinobacteria were frequently enriched in the successful treatment sites, suggesting that Actinobacteria taxa could be indicators for HLB suppression properties in the soil.ConclusionOur results suggest that microbiome manipulation, either through changes in the management practices or microbial amendment, can increase the suppressive potential of soils, resulting in the reduction in CLas titer and potentially leading to HLB suppression in citrus groves.

Long term application of plant growth-promoting bacterium improved grain weight and reduced arsenic accumulation in rice grain: A comparison of 10 bacteria.

Rice (Oryza sativa L.) is one of the main food crops, it plays an important role in the human diet. Arsenic (As) contamination in paddy soil inhibits rice growth and reduces rice yield seriously. In addition, As accumulated in rice grains was harmful to human health through the food chain. Using the exogenous method to alleviate As stress and reduce As accumulation in rice grain is one of the potential ways to achieve food safety in polluted farmland. In the present study, 10 bacteria was applied to evaluate the effects of plant growth-promoting bacteria (PGPBs) on rice growth and As accumulation in rice grain. The results showed higher levels of As inhibited PGPB growth, the most tolerant and sensitive bacteria were Bj05 and Ls09, with the growth reduction of 16.9% and 96.7% under 50mM As, respectively. Most of 10 PGPBs enhanced rice growth and improved rice grain weight under As exposure, among them, Ts06 showed the most effective one. Six of 10 PGPBs reduced rice grain As levels significantly, the highest reduction of grain As was observed in Ts06 inoculated rice, with grain As deceasing to 46.3% of the control. Bj05 was the only one which caused the increase in grain As of Yangdao 6. The Pearson correlation analysis showed grain As concentration negatively correlated with leave As concentration, while did not correlated with total As accumulated in shoot, and soil available As and P. The present results indicated that some PGPBs inhibited As translocation from leave to grain, thus reduced As accumulation in rice grain. Ts06 was suggested to be a candidate as microbial amendments for As-contaminated paddy fields.

Fungi Can Be More Effective than Bacteria for the Bioremediation of Marine Sediments Highly Contaminated with Heavy Metals.

The contamination of coastal marine sediments with heavy metals (HMs) is a widespread phenomenon that requires effective remediation actions. Bioremediation based on the use of bacteria is an economically and environmentally sustainable effective strategy for reducing HM contamination and/or toxicity in marine sediments. However, information on the efficiency of marine-derived fungi for HM decontamination of marine sediments is still largely lacking, despite evidence of the performance of terrestrial fungal strains on other contaminated matrixes (e.g., soils, freshwater sediments, industrial wastes). Here, we carried out for the first time an array of parallel laboratory experiments by using different combinations of chemical and microbial amendments (including acidophilic autotrophic and heterotrophic bacteria, as well as filamentous marine fungi) for the bioremediation of highly HM-contaminated sediments of the Portman Bay (NW Mediterranean Sea), an area largely affected by long-term historical discharges of mine tailings. Our results indicate that the bioleaching performance of metals from the sediment is based on the addition of fungi (Aspergillus niger and Trichoderma sp.), either alone or in combination with autotrophic bacteria, was higher when compared to other treatments. In particular, fungal addition allowed obtaining bioleaching yields for As eight times higher than those by chemical treatments and double compared with the addition of bacteria alone. Moreover, in our study, the fungal addition was the only treatment allowing effective bioleaching of otherwise not mobile fractions of Zn and Cd, thus overtaking bacterial treatments. We found that the lower the sediment pH reached by the experimental conditions, as in the case of fungal addition, the higher the solubilization yield of metals, suggesting that the specific metabolic features of A. niger and Trichoderma sp. enable lowering sediment pH and enhance HM bioleaching. Overall, our findings indicate that fungi can be more effective than acidophilic autotrophic and heterotrophic bacteria in HM bioleaching, and as such, their use can represent a promising and efficient strategy for the bioremediation of marine sediments highly contaminated with heavy metals.

Senegalia senegal (L.) Britton Response to Microbial and Manure Amendments for the Rehabilitation of Waste Rock Dumps in the Essakane Gold Mining Site, Burkina Faso

Senegalia senegal (L.) Britton (Fabaceae) is a widespread, multipurpose tree capable of colonizing disturbed Sub-Saharan mining sites given its adaptations to arid lands. The purpose of this study was to determine the potential of the association of microbial and/or manure amendments with S. senegal seedlings for the effective rehabilitation of the environment post mining. A multi-year factorial experiment involving this species was conducted in a nursery and on waste rock dumps (Essakane gold mine, NE Burkina Faso). Inoculation with arbuscular mycorrhizal (AM) fungi (native isolate Rhizophagus aggregatus DAOM2277128; commercial isolate Rhizophagus irregularis DAOM197198) and Mesorhizobium plurifarium strain ORS3588 was conducted on S. senegal seedlings. These were planted in black polythene bags filled with three substrate types: 100% sandy soil (substrate A); 75% sandy soil, 25% manure (substrate B); and 50% sandy soil, 50% manure (substrate C). Seedlings were then out-planted on waste rock to determine whether microbial inoculation improves their growth and survival rates. Under nursery conditions, manure-enriched substrates harboured less nodulation and AM colonization, but substantially increased plant height, and dry mass compared to un-amended substrate. Inoculation on manure-enrich substrates did not consistently increase root AM colonization and plant growth parameters among treatments. Plants that were inoculated with R. aggregatus alone or with R. irregularis or Mesorhizobium plurifarium ORS3588 showed the greatest increase in growth variables. On un-amended substrates, inoculation with R. aggregatus in combination with M. plurifarium or R. irregularis significantly enhanced root colonization rates, without altering plant growth parameters. Yet, inoculation with R. irregularis or M. plurifarium alone did not elicit increases in these parameters, although nodulation was greatly improved by the latter treatment. In field conditions, plant growth and survival were reduced under high rate manure amendments, likely due to less AM colonization and root nodulation that was observed for these treatments in nursery before out-planting. Strongly colonized plants on the un-amended substrate and moderately amended substrate showed greater survival after out-planting. Our results support the general conclusion that microbial inoculation and manure-enriched substrates are a viable option for mining site rehabilitation using S. senegal. They also suggest that manure amendments in forest nurseries should be cautiously applied given that high rates may impede establishment of plant symbioses, thereby affecting their performance on waste rock dumps following out-planting.

Vermicomposting with microbial amendment: implications for bioremediation of industrial and agricultural waste.

Improved agricultural practices and rapid industrialization have led to huge waste generation, and the management of this waste is becoming a global concern. The process of vermicomposting has emerged as a method of choice for converting waste into useful manure, with evidence of increase in crop productivity. During vermi-composting, the collective activities of decomposing microorganisms and earthworms lead to the humification of organic/inorganic waste, thereby generating the final product called vermicompost. Different types of industrial wastes such as waste from paper industries, tanneries, sugar mills, and pulp and textile industries have been effectively converted to vermicompost and successfully used to improve plant growth. The vermicompost thus formed was also demonstrated to increase the production of pharmaceutically important plant secondary meta-bolites such as withanolides and polyunsaturated fatty acids. Microbial amendment with different bacterial and fungal strains during vermicomposting further proves to be beneficial by increasing nitrogen content, decomposing organic waste, providing aeration, and stabilizing the vermicompost. These microorganisms after passing through the earthworm's intestine increase in numbers in the vermicast, thus becoming enriched in vermi-compost, which is particularly important for their use as biofertilizers. The precise role of different microbial pretreatments in improving the quality of vermicompost generated from industrial and agricultural waste is, however, not completely understood. To fill this gap in knowledge, the present article aims to review published literature to highlight the potential of microbial amendment during vermicomposting for bioremediation of industrial and agricultural waste. Microbial pre-composting followed by vermicomposting emerges as an eco-friendly and economical approach for managing agricultural and industrial waste.

A Multi-Sensor Mini-Bioreactor to Preselect Silage Inoculants by Tracking Metabolic Activity in situ During Fermentation.

The microbiome in silage may vary substantially from the onset to the completion of fermentation. Improved additives and inoculants are being developed to accelerate the ensiling process, to enhance fermentation quality, and to delay spoilage during feed-out. However, current methods for preselecting and characterizing these amendments are time-consuming and costly. Here, we have developed a multi-sensor mini-bioreactor (MSMB) to track microbial fermentation in situ and additionally presented a mathematical model for the optimal assessment among candidate inoculants based on the Bolza equation, a fundamental formula in optimal control theory. Three sensors [pH, CO2, and ethanol (EtOH)] provided data for assessment, with four additional sensors (O2, gas pressure, temperature, and atmospheric pressure) to monitor/control the fermentation environment. This advanced MSMB is demonstrated with an experimental method for evaluating three typical species of lactic acid bacteria (LAB), Lentilactobacillus buchneri (LB) alone, and LB mixed with Lactiplantibacillus plantarum (LBLP) or with Enterococcus faecium (LBEF), all cultured in De Man, Rogosa, and Sharpe (MRS) broth. The fermentation process was monitored in situ over 48 h with these candidate microbial strains using the MSMB. The experimental results combine acidification characteristics with production of CO2 and EtOH, optimal assessment of the microbes, analysis of the metabolic sensitivity to pH, and partitioning of the contribution of each species to fermentation. These new data demonstrate that the MSMB associated with the novel rapid data-processing method may expedite development of microbial amendments for silage additives.

The Influence of Applying Microbial Amendments to Soil and Plants on the Microbial Diversity in the Rhizosphere Soil of Garlic

With the environmental problems brought about by the excessive use of fertilizers and pesticides, numerous biological amendments have been developed and used in recent years. This study, through in-depth analysis of the effects of two different microbial amendments on the microbial diversity in the garlic rhizosphere, provides a theoretical basis and data support for farmers to select microbial amendments. In the experiment, two different microbial amendments were applied to garlic, and its rhizosphere soil was collected after 10, 20, 30, and 40 days. The polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze bacterial diversity in the garlic rhizosphere soil. The total abundance and diversity of microbial flora in the rhizosphere soil of garlic increased after application of microbial amendments to soil or plants. Plant growth was significantly better in the soil treatment than the plant treatment and the water control. The two dominant bacteria of uncultured gamma proteobacterium and Uncultured Gemmatimonadete existed only in the soil treatment. After 40 day of treatment, the abundance in the rhizosphere soil of these four bacterial strains (Uncultured Bacillus sp. clone D.an-22, Mesorhizobium sp., uncultured gamma proteobacterium, and Pseudomonas boreopolis) was greater in the soil than the plant treatment and the control. The irrigation of microbial amendments not only influenced the structure and abundance of rhizosphere microorganisms, and also promoted the colonization by microorganisms. The five bacterial strains of uncultured gamma proteobacterium, Uncultured Gemmatimonadetes, Uncultured Bacillus sp. clone D.an-22, Mesorhizobium sp., Pseudomonas boreopolis could facilitate the growth and enhance resistance of garlic, establishing a foundation for the use of microbial amendments and providing new ideas and methods for environmental management and protection.

Effects of matrix modification and bacteria amendment on the treatment efficiency of municipal tailwater pollutants by modified vertical flow constructed wetland

Although vertical flow constructed wetland (VFCW) has great potentials for degradation of water contaminants, traditional VFCW has limited removal efficiencies for pollutants. This study constructed three sets of modified VFCW systems, including VFCW-A with matrix-modification using mixture of biochar and activated carbon, VFCW-B with microbial amendment using denitrifying bacteria, and VFCW-C with combined treatments of both. Their removal efficiencies for various pollutants in synthetic municipal tailwater were investigated. Results showed that the removal efficiencies for NH4–N, NO3–N, total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) by VFCW-C were higher than VFCW-B throughout the experimental period, indicating that matrix-modification could improve the VFCW performance. The higher removal efficiencies for TN, TP, and COD by VFCW-C than VFCW-A also suggested the effectiveness of microbial amendment in VFCW. However, the improved removal for NO3–N by VFCW-C over VFCW-A became less obvious at later operation stage due to insufficient carbon source. All three VFCWs achieved their best removal efficiency when carbon source was supplemented at CH3COO−/TN ratio of 0.5. Our study suggested that the combined treatment of matrix-modification using biochar/activated carbon mixture and microbial amendment using denitrifying bacteria could effectively enhance the treatment efficiency of VFCW systems for tailwater pollutants from sewage plant.

Impact of Soil Microbial Amendments on Tomato Rhizosphere Microbiome and Plant Growth in Field Soil.

There is increased interest by the agricultural industry in microbial amendments that leverage natural beneficial interactions between plants and soil microbes to improve crop production. However, translating fundamental knowledge from laboratory experiments into efficient field application often has mixed results, and there is less clarity about the interaction between added microbes and the native microbial community, where microorganisms belonging to the same phylogenic clades often reside. In this study, four commercially available microbial amendments were examined in two greenhouse experiments using field soil to assess their impact on tomato plant growth and the native soil microbial communities. The amendments contained different formulations of plant growth-promoting bacteria (Lactobacilli, Rhizobia, etc.), yeasts, and mycorrhizal fungi. The application of the tested amendments in greenhouse conditions resulted in no significant impact on plant growth. A deeper statistical analysis detected variations in the microbial communities that accounted only for 0.25% of the total species, particularly in native taxa not related to the inoculated species and represented less than 1% of the total variance. This suggests that under commercial field conditions, additional confounding variables may play a role in the efficacy of soil microbial amendments. This study confirms the necessity of more in-depth validation requirements for the formulations of soil microbial amendments before delivery to the agricultural market in order to leverage their benefits for the producers, the consumers, and the environment.

Native soil microbial amendments generate trade‐offs in plant productivity, diversity, and soil stability in coastal dune restorations

Given the important role that soil microbes play in structuring plant communities and mediating ecosystem functions, there is growing interest in harnessing microbial communities to restore degraded ecosystems. Dune restorations, in particular, may benefit from native soil amendments because microbial diversity and abundance are very low in unvegetated areas. In an outdoor mesocosm experiment simulating Texas Gulf Coast dune restorations, we tested how native soil microbial amendments and restored diversity of foundational grasses influenced three key restoration responses: plant performance, plant diversity (including the colonization of native forbs), and soil stability. We found that native microbial amendments increased plant diversity and have the potential to increase soil stability, but this came at the cost of decreased plant biomass. Our results suggest that soil enemies in the native microbial amendments increased plant diversity by decreasing the performance of the dominant grass species and that arbuscular mycorrhizal fungi in the native microbial amendments increased the density of fungal hyphae in the soil, which can increase soil stability. Depending on the goals of the restoration, native soil microbial amendments may be a simple and inexpensive method to provide restoration benefits.

Microbial amendments alter protist communities within the soil microbiome

Plant-beneficial microbes improve while pathogens reduce plant performance. When introduced in soils, such microbes can induce entire microbiome changes. However, the impact of those microbial introductions on protists – key predators within the soil microbiome – remain unknown. Here, we tracked how soil protists respond to bacterial (Bacillus and Ralstonia) and fungal (Trichoderma and Fusarium) introductions, with both microbial groups represented by one beneficial and one pathogenic taxon. We found that plant-beneficial Bacillus bacteria change the protist community structure. This community-shift was likely induced by an increased fungi/bacteria ratio, supported by a negative correlation of the fungi/bacteria ratio with the relative abundance of phagotrophic protists across all treatments. Our results indicate that microbial introductions can impact protist communities, thereby altering microbiome-derived multi-functionality.