Cecal Microbiota Development and Physiological Responses of Broilers Following Early Life Microbial Inoculation Using Different Delivery Methods and Microbial Sources.

Broilers in intensive systems may lack commensal microbes that have coevolved with chickens in nature. This study evaluated the effects of microbial inocula and delivery methods applied to day-old chicks on the development of the cecal microbiota. Specifically, chicks were inoculated with cecal contents or microbial cultures, and the efficacies of three delivery methods (oral gavage, spraying inoculum into the bedding, and cohousing) were evaluated. Also, a competitive study evaluated the colonization ability of bacteria sourced from extensive or intensive poultry production systems. The microbiota of inoculated birds presented higher phylogenetic diversity values (PD) and higher relative abundance values of Bacteroidetes, compared with a control. Additionally, a reduction in the ileal villus height/crypt depth ratio and increased cecal IL-6, IL-10, propionate, and valerate concentrations were observed in birds that were inoculated with cecal contents. Across the experiments, the chicks in the control groups presented higher relative abundance values of Escherichia/Shigella than did the inoculated birds. Specific microbes from intensively or extensively raised chickens were able to colonize the ceca, and inocula from intensive production systems promoted higher relative abundance values of Escherichia/Shigella. We concluded that Alistipes, Bacteroides, Barnesiella, Mediterranea, Parabacteroides, Megamonas, and Phascolarctobacterium are effective colonizers of the broiler ceca. In addition, oral gavage, spray, and cohousing can be used as delivery methods for microbial transplantation, as indicated by their effects on the cecal microbiota, intestinal morphology, short-chain fatty acids concentration, and cytokine/chemokine levels. These findings will guide future research on the development of next-generation probiotics that are able to colonize and persist in the chicken intestinal tract after a single exposure. IMPORTANCE The strict biosecurity procedures employed in the poultry industry may inadvertently hinder the transmission of beneficial commensal bacteria that chickens would encounter in natural environments. This research aims at identifying bacteria that can colonize and persist in the chicken gut after a single exposure. We evaluated different microbial inocula that were obtained from healthy adult chicken donors as well as three delivery methods for their effects on microbiota composition and bird physiology. In addition, we conducted a competitive assay to test the colonization abilities of bacteria sourced from intensively versus extensively raised chickens. Our results indicated that some bacteria are consistently increased in birds that are exposed to microbial inoculations. These bacteria can be isolated and employed in future research on the development of next-generation probiotics that contain species that are highly adapted to the chicken gut.

Deciphering the Synergies of Reductive Soil Disinfestation Combined with Biochar and Antagonistic Microbial Inoculation in Cucumber Fusarium Wilt Suppression Through Rhizosphere Microbiota Structure.

Application of reductive soil disinfestation (RSD), biochar, and antagonistic microbes have become increasingly popular strategies in a microbiome-based approach to control soil-borne diseases. The combined effect of these remediation methods on the suppression of cucumber Fusarium wilt associated with microbiota reconstruction, however, is still unknown. In this study, we applied RSD treatment together with biochar and microbial application of Trichoderma and Bacillus spp. in Fusarium-diseased cucumbers to investigate their effects on wilt suppression, soil chemical changes, microbial abundances, and the rhizosphere communities. The results showed that initial RSD treatment followed by biochar amendment (RSD-BC) and combined applications of microbial inoculation and biochar (RSD-SQR-T37-BC) decreased nitrate concentration and raised soil pH, soil organic carbon (SOC), and ammonium in the treated soils. Under RSD, the applications of Bacillus (RSD-SQR), Trichoderma (RSD-T37), and biochar (RSD-BC) suppressed wilt incidence by 26.8%, 37.5%, and 32.5%, respectively, compared to non-RSD treatments. Moreover, RSD-SQR-T37-BC and RSD-T37 caused greater suppressiveness of Fusarium wilt and F. oxysporum by 57.0 and 33.5%, respectively. Rhizosphere beta diversity and alpha diversity revealed a difference between RSD-treated and non-RSD microbial groups. The significant increase in the abundance, richness, and diversity of bacteria, and the decrease in the abundance and diversity of fungi under RSD-induced treatments attributed to the general suppression. Identified bacterial (Bacillus, Pseudoxanthomonas, Flavobacterium, Flavisolibacter, and Arthrobacter) and fungal (Trichoderma, Chaetomium, Cladosporium, Psathyrella, and Westerdykella) genera were likely the potential antagonists of specific disease suppression for their significant increase of abundances under RSD-treated soils and high relative importance in linear models. This study infers that the RSD treatment induces potential synergies with biochar amendment and microbial applications, resulting in enhanced general-to-specific suppression mechanisms by changing the microbial community composition in the cucumber rhizosphere.

Optimistic contributions of plant growth-promoting bacteria for sustainable agriculture and climate stress alleviation.

Global climate change is the major cause of abiotic and biotic stresses that have adverse effects on agricultural productivity to an irreversible level, thus threatening to limit gains in production and imperil sustainable agriculture. These climate change-induced abiotic stresses, especially saline, drought, extreme temperature, and so on affect plant morphological, physiological, biochemical, and metabolic characteristics through various pathways and mechanisms, ultimately hindering plant growth, development, and productivity. However, overuse and other inappropriate uses of agrochemicals are not conducive to the protection of natural resources and the environment, thus hampering sustainable agricultural development. With the vigorous development of modern agriculture, the application of plant growth-promoting bacteria (PGPB) can better ensure sustainable agriculture, due to their ability to improve soil properties and confer stress tolerance in plants. This review deciphered the underlying mechanisms of PGPB involved in enhancing plant stress tolerance and performance under various abiotic and biotic stresses. Moreover, the recent advancements in PGPB inoculation techniques, the commercialization of PGPB-based technology and the current applications of PGPB in sustainable agriculture were extensively discussed. Finally, an outlook on the future directions of microbe-aided agriculture was pointed out. Providing insights into plant-PGPB interactions under biotic and abiotic stresses and offering evidence and strategies for PGPB better commercialization and implementation can inspire the development of innovative solutions exploiting PGPB under climatological conditions.

Influence of microbial inoculants on co-composting of lignocellulosic crop residues with farm animal manure: A review.

The rapidly developing agro-industry generates huge amounts of lignocellulosic crop residues and animal manure worldwide. Although co-composting represents a promising and cost-effective method to treat various agricultural wastes simultaneously, poor composting efficiency prolongs total completion time and deteriorates the quality of the final product. However, supplementation of the feedstock with beneficial microorganisms can mitigate these negative effects by facilitating the decomposition of recalcitrant materials, enhancing microbial enzyme activity, and promoting maturation and humus formation during the composting process. Nevertheless, the influence of microbial inoculation may vary greatly depending on certain factors, such as start-up parameters, structure of the feedstock, time of inoculation, and composition of the microbial cultures used. The purpose of this contribution is to review recent developments in co-composting procedures involving different lignocellulosic crop residues and farm animal manure combined with microbial inoculation strategies. To evaluate the effectiveness of microbial additives, the results reported in a large number of peer-reviewed articles were compared in terms of composting process parameters (i.e., temperature, microbial activity, total organic carbon and nitrogen contents, decomposition rate of lignocellulose fractions, etc.) and compost characteristics (humification, C/N ratio, macronutrient content, and germination index). Most studies confirmed that the use of microbial amendments in the co-composting process is an efficient way to facilitate biodegradation and improve the sustainable management of agricultural wastes. Overall, this review paper provides insights into various inoculation techniques, identifies the limitations and current challenges of co-composting, especially with microbial inoculation, and recommends areas for further research in this field.

Plant growth-promoting microbes improve stormwater retention of a newly-built vertical greenery system.

On-site decentralized urban stormwater management has gained significant momentum in urban planning. Recently, vegetated roofs have been recommended as a viable decentralized stormwater management system and nature-based solution to meet the challenge of urban floods. However, as another type of unconventional green infrastructure, vertical greenery systems (VGS), also known as vegetated facades, have received much less research attention. Even though some researchers suggest that stormwater management by VGS is comparable to that of vegetated roofs, empirical evidence to substantiate this claim is limited. In this study, we conducted rain simulations on newly-built vegetation containers with water storage compartments. These vegetation containers were designed to be incorporated into a VGS specifically for stormwater management. We tested variables that could influence water retention efficiency and evapotranspiration of the containers under field conditions, i.e., inoculation of plant growth-promoting microbes (PGPMs) (Rhizophagus irregularis and Bacillus amyloliquefaciens), different substrate types (sandy loam and reed-based substrate), simulated rain quantity, natural precipitation, substrate moisture, and air temperature. The inoculation of PGPMs significantly reduced runoff quantity from the vegetation containers. Meanwhile, the well-ventilated sandy-loam substrate significantly reduced the remaining water in the water storage compartments over 1-week periods between rain simulation events, achieving high water-use efficiency. The selected microbes were established successfully in the containers and promoted the growth of 2 out of 5 plant species. R. irregularis colonization responded to substrate type and host plant species, while B. amyloliquefaciens population density in the substrate did not respond to these factors. Environmental conditions, such as antecedent substrate moisture, air temperature, and natural precipitation also influenced the efficiency of stormwater retention and/or evapotranspiration. In conclusion, this study provides instructive and practical insights to reduce urban flood risk by using VGS.

Trichoderma strains accelerate maturation and increase available phosphorus during vermicomposting enriched with rock phosphate.

AIMS: To suggest microbial inoculation as a tool to shorten organic residues stabilization and increase rock phosphate (RP) solubilization through vermicomposting, thus increasing nutrient content in plants and making it more appealing to farmers. Two Trichoderma strains were inoculated alone or combined in a RP apatite-enriched vermicompost. Stability and plant-available phosphorus levels were monitored for 120 days. METHODS AND RESULTS: Observable higher total organic carbon reduction in the treatment with the combined Trichoderma strains, followed by the inoculation with T. asperellum and T. virens. Combined Trichoderma and inoculation with T. virens increased humic acids (HA) content in 38·2 and 25·0%, respectively; non-inoculated vermicompost with T. asperellum increased it by 15·0%. The combined Trichoderma strains and T. virens achieved the stability index based on the humic/fulvic acids (HA/FA) ratio after 120 days. T. asperellum, combined Trichoderma and T. virens increased the citric acid soluble-P content in 83·2, 62·2 and 49·5%, respectively, compared to the non-inoculated vermicompost. CONCLUSIONS: Inoculation with combined T. asperellum and T. virens efficiently accelerated vermicompost stabilization; T. asperellum increased the citric acid soluble-P in the final product. SIGNIFICANCE AND IMPACT OF THE STUDY: Combined Trichoderma inoculation and RP enrichment improves the vermicompost quality, increasing HA and citric acid soluble-P, recycling organic waste nutrients and reducing agricultural dependence on phosphate fertilizers.

Inoculation with rumen fluid in early life as a strategy to optimize the weaning process in intensive dairy goat systems.

Ruminants are born with an undeveloped physical, metabolic, and microbial rumen. Rumen development is limited under artificial rearing systems when newborn animals are separated from the dam, fed on milk replacer, and weaned at an early age. This study aims to evaluate the effects of early-life inoculation of young ruminants with rumen fluid from adult animals. Eighty newborn goat kids were randomly allocated to 1 of 4 experimental treatments and inoculated daily from d 1 to wk 11 with autoclaved rumen fluid (AUT), fresh rumen fluid obtained from adult goats fed either a forage diet (RFF) or concentrate-rich diet (RFC), or absence of inoculation (CTL). Goat kids were artificially reared with ad libitum access to milk replacer, starter concentrate, and forage hay. Blood was sampled weekly and rumen microbial fermentation was monitored at 5 (preweaning), 7 (weaning), and 9 wk of age (postweaning). Results indicated that inoculation with fresh rumen fluid accelerated the rumen microbial and fermentative development before weaning. As a result, RFC and RFF animals had higher solid feed intake (+73%), rumen concentrations of ammonia-N (+26%), total volatile fatty acids (+46%), butyrate (+50%), and plasma ß-hydroxybutyrate (+48%), and lower milk intake (-6%) than CTL and AUT animals at wk 5. Inoculation with fresh inoculum also promoted early rumen colonization by a complex and abundant protozoal community, whereas CTL animals remained protozoa free. Although all kids experienced moderate growth retardation during 1 wk after weaning, inoculation with fresh rumen fluid favored the weaning process, leading to 2.2 times higher weight gain than CTL and AUT animals during wk 8. Some of these advantages were retained during the postweaning period and RFF and RFC animals showed higher forage intake (up to +44%) than CTL and AUT animals with no detrimental effects on feed digestibility or stress levels. The superior microbial load of RFC compared with RFF inoculum tended to provide further improvements in terms of forage intake, plasma ß-hydroxybutyrate, and rumen protozoa, whereas AUT inoculation provided minor (if any) advantages with respect to CTL animals. Although no differences were noted on animal growth, this study suggests that early life inoculation of goat kids with rumen microbiota can represent an effective strategy to accelerate the rumen development, facilitating a smooth transition from milk to solid feed and to the potential implementation of early weaning strategies.

Effect of microbial inoculation and particle size on fermentation profile, aerobic stability, and ruminal in situ starch degradation of high-moisture corn ensiled for a short period.

Dairy farmers are often challenged with the need to feed high-moisture corn (HMC) after less than 30 d of fermentation. The objective this study was to assess the effects of microbial inoculation and particle size on fermentation profile, aerobic stability, and ruminal in situ starch degradation of HMC ensiled for a short period. High-moisture corn was harvested, coarsely ground (3,798 ± 40 µm, on average) or finely ground (984 ± 42 µm, on average), then ensiled in quadruplicate vacuum pouches untreated (CON) or with the following treatments: Lactobacillus plantarum CH6072 at 5 × 104 cfu/g and Enterococcus faecium CH212 at 5 × 104 cfu/g of fresh forage (LPEF); or Lactobacillus buchneri LB1819 at 7.5 × 104 cfu/g and Lactococcus lactis O224 at 7.5 × 104 cfu/g (LBLL). Silos were allowed to ferment for 14 or 28 d. Ruminal in situ starch degradation increased when HMC was finely ground. In addition, in situ starch degradation was greater and aerobic stability increased approximately 5-fold with LBLL compared with CON and LPEF. An interaction between microbial inoculation and storage length occurred for lactic acid. At 14 d, concentrations of lactic acid were greatest in LPEF and lowest in LBLL. Lactic acid concentrations increased from 14 to 28 d with CON and LPEF, but decreased with LBLL. At 28 d, concentrations of lactic acid were lower in LBLL compared with CON and LPEF. An interaction between particle size, microbial inoculation, and storage length occurred for acetic acid and ammonia-N. At 14 and 28 d, acetic acid concentrations were greatest in finely ground LBLL followed by coarsely ground LBLL. Ammonia-N concentrations increased across all treatments from 0 to 28 d. At 14 and 28 d, concentrations of ammonia-N were greatest in finely ground LBLL and lowest in coarsely ground CON and coarsely ground LPEF. Results from this study suggest that L. buchneri LB1819 can produce acetic acid in as little as 14 d, and that by 28 d, it has the potential to improve the aerobic stability of HMC. Additionally, results indicate that L. buchneri LB1819 has the potential to improve ruminal degradation of starch by 28 d of storage. Finally, results confirm enhanced fermentation and improved ruminal starch degradation with finely ground HMC by 28 d of storage.

Compost biofortification with diazotrophic and P-solubilizing bacteria improves maturation process and P availability.

BACKGROUND: Phosphorus-containing fertilizers play an important role in tropical agriculture owing to the well documented shortage of plant-available P in soils. Traditional P fertilizer production is based on chemical processing of insoluble rock phosphate (RP), which includes an acid treatment at high temperature. Processing the RP increases fertilizer costs, making it unavailable for undercapitalized and typically family-based farmers. Biotechnological methods have been proposed as an alternative to increase phosphate availability in RP. In this study, Burkholderia silvatlantica and Herbaspirillum seropedicae were co-inoculated into an RP-enriched compost with the aim of determining the effects of this technology on the levels of phosphatase activities and release of plant-available P. RESULTS: Inoculation of both microorganisms resulted in higher organic matter decomposition and higher humic acid formation in composting. Herbaspirillum seropedicae was the most promising microorganism for the production of acid and alkaline phosphatase enzymes. Both microorganisms presented potential to increase the supply of P from poorly soluble sources owing to increased levels of water-soluble P and citric acid P. CONCLUSION: Burkholderia silvatlantica and H. seropedicae in RP-enriched compost may represent an important biotechnological tool to reduce the overall time required for composting and increase the supply of P from poorly soluble sources. © 2016 Society of Chemical Industry.

Microbial inoculation of seed for improved crop performance: issues and opportunities.

There is increasing interest in the use of beneficial microorganisms as alternatives to chemical pesticides and synthetic fertilisers in agricultural production. Application of beneficial microorganisms to seeds is an efficient mechanism for placement of microbial inocula into soil where they will be well positioned to colonise seedling roots and protect against soil-borne diseases and pests. However, despite the long history of inoculation of legume seeds with Rhizobia spp. and clear laboratory demonstration of the ability of a wide range of other beneficial microorganisms to improve crop performance, there are still very few commercially available microbial seed inoculants. Seed inoculation techniques used for research purposes are often not feasible at a commercial scale and there are significant technical challenges in maintaining viable microbial inocula on seed throughout commercial seed treatment processes and storage. Further research is needed before the benefits of a wide range of environmentally sensitive potential seed inoculants can be captured for use in agriculture, ecosystem restoration and bioremediation. There is no single solution to the challenge of improving the ability of seed inoculants to establish and function consistently in the field. Development of novel formulations that maintain the viability of both inoculant and seed during storage will result from multidisciplinary research in microbial and seed physiology and adjuvant chemistry.

Effects of exogenous thermophilic bacteria and ripening agent on greenhouse gas emissions, enzyme activity and microbial community during straw composting.

This research examined the impact of exogenous thermophilic bacteria and ripening agents on greenhouse gas (GHG) emission, enzyme activity, and microbial community during composting. The use of ripening agents alone resulted in a 30.9 % reduction in CO2 emissions, while the use of ripening agents and thermophilic bacteria resulted in a 50.8 % reduction in N2O emissions. Pearson's analysis showed that organic matter and nitrate nitrogen were the key parameters affecting GHG emissions. There was an inverse correlation between CO2 and CH4 releases and methane monooxygenase α subunit and N2O reductase activity (P<0.05). Additionally, N2O emissions were positively related to ß-1, 4-N-acetylglucosaminidase, and ammonia monooxygenase activity (P<0.05). Deinococcota, Chloroflexi, and Bacteroidota are closely related to CO2 and N2O emissions. Overall, adding thermophilic bacteria represents an effective strategy to mitigate GHG emissions during composting.

Mechanism underlying effects of cellulose-degrading microbial inoculation on amino acid degradation and biosynthesis during composting.

Amino acids are essential organic compounds in composting products. However, the mechanism underlying the amino acid metabolism during composting remains unclear. This study aims at exploring the impacts of inoculating cellulose-degrading microbes on amino acid metabolism during composting with mulberry branches and silkworm excrements. Cellulose-degrading microbial inoculation enhanced amino acid degradation by 18%-43% by increasing protease and sucrase activities and stimulating eight amino acid degradation pathways from the initial to thermophilic phases, with Enterococcus, Saccharomonospora, Corynebacterium being the dominant bacterial genera, but stimulated amino acid production by 54% by increasing sucrase and urease activities, decreasing ß-glucosidase activities, and stimulating twenty-two amino acid synthesis pathways at the mature phase, with Thermobifida, Devosia, and Cellulosimicrobium being the dominant bacterial genera. The results suggest that cellulose-degrading microbial inoculation enhances amino acid degradation from the initial to thermophilic phases and biosynthesis at the mature phase, thereby improving the quality of organic fertilizer.

Inoculation with Bacillus thuringiensis reduces uptake and translocation of Pb/Cd in soil-wheat system: A life cycle study.

Microbial inoculation is an important strategy to reduce the supply of heavy metals (HMs) in soil-crop systems. However, the mechanisms of microbial inoculation for the availability of HMs in soil and their accumulation/transfer in crops remain unclear. Here, the inhibitory effect of inoculation with Bacillus thuringiensis on the migration and accumulation of Pb/Cd in the soil-wheat system during the whole growth period was investigated by pot experiments. The results showed that inoculation with Bacillus thuringiensis increased soil pH and available nutrients (including carbon, nitrogen, and phosphorus), and enhanced the activities of nutrient-acquiring enzymes. Dominance analysis showed that dissolved organic matter (DOM) is the key factor affecting the availability of HMs. The content of colored spectral clusters and humification characteristics of DOM were significantly improved by inoculation, which is conducive to reducing the availability of Pb/Cd, especially during the flowering stage, the decrease was 12.8 %. Inoculation decreased Pb/Cd accumulation in the shoot and the transfer from root to shoot, with the greatest decreases at the jointing and seedling stages (27.0-34.1 % and 6.9-11.8 %), respectively. At the maturity stage, inoculation reduced the Pb/Cd accumulation in grain (12.9-14.7 %) and human health risk (4.1-13.2 %). The results of Pearson correlation analysis showed that the availability of Pb/Cd was positively correlated with the humification of DOM. Least square path model analysis showed that Bacillus thuringiensis could significantly reduce Pb/Cd accumulation in the grain and human health risks by regulating DOM spectral characteristics, the availability of HMs in soil and metals accumulation/transport in wheat at different growth stages. This study revealed the inhibition mechanism of Bacillus thuringiensis on migration of Pb/Cd in a soil-wheat system from a viewpoint of a full life cycle, which offers a valuable reference for the in-situ remediation of HM-contaminated soil and the safe production of food crops in field.

The impact of microbial inoculants on large-scale composting of straw and manure under natural low-temperature conditions.

Understanding large-scale composting under natural conditions is essential for improving waste management and promoting sustainable agriculture. In this study, corn straw (400 tons) and pig manure (200 tons) were composted with microbial inoculants. The thermophilic phase of composting lasted for fourteen weeks, resulting in an alkaline final product. Microbial systems with low-temperature initiation and high-temperature fermentation played a crucial role in enhancing lignocellulose degradation and humic substances (HS) formation. Adding microbes, including Rhodanobacter, Pseudomonas, and Planococcus, showed a positive correlation with degradation rates of cellulose, hemicellulose, and lignin. Bacillus, Planococcus, and Acinetobacter were positively correlated with HS formation. Microorganisms facilitated efficient hydrolysis of lignocelluloses, providing humic precursors to accelerate composting humification through phenolic protein and Maillard pathways. This study provides significant insights into large-scale composting under natural conditions, contributing to the advancement of waste management strategies and the promotion of sustainable agriculture.

Addition of cellulose and hemicellulose degrading microorganisms intensified nitrous oxide emission during composting.

This study aims to clarify the mechanisms underlying effects of inoculating cellulose and hemicellulose-degrading microorganisms on nitrous oxide (N2O) emissions during composting with silkworm excrement and mulberry branches. Inoculation with cellulose and hemicellulose-degrading microorganisms resulted in significant increases of total N2O emission by 10.4 ± 2.0 % (349.1 ± 6.2 mg N kg-1 dw) and 26.7 ± 2.1 % (400.6 ± 6.8 mg N kg-1 dw), respectively, compared to the control (316.3 ± 3.6 mg N kg-1 dw). The stimulation of N2O emission was attributed to the enhanced contribution of ammonia-oxidizing bacteria (AOB) and denitrifying bacteria to N2O production, as evidenced by the increased AOB amoA and denitrifying nirK gene abundances. Moreover, microbial inoculation stimulated N2O reduction to N2 owing to increased abundances of nosZⅠ and nosZⅠⅠ genes. These findings highlight the necessity to develop cost-effective and environmentally friendly strategies to reduce N2O emissions when cellulose and hemicellulose-degrading microorganisms are inoculated during composting.

Limited efficacy of a commercial microbial inoculant for improving growth and physiological performance of native plant species.

Soil microbial inoculants are increasingly being explored as means to improve soil conditions to facilitate ecological restoration. In southwestern Western Australia, highly biodiverse Banksia woodland plant communities are increasingly threatened by various factors including climate change, land development and mining. Banksia woodland restoration is necessary to conserve this plant community. The use of microbial inoculation in Banksia woodland restoration has not yet been investigated. Here, we evaluated the efficacy of a commercial microbial inoculant (GOGO Juice, Neutrog Australia Pty Ltd) for improving the performance of 10 ecologically diverse Banksia woodland plant species in a pot experiment. Plants were subjected to one of two watering regimes (well-watered and drought) in combination with microbial inoculation treatments (non-inoculated and inoculated). Plants were maintained under these two watering treatments for 10 weeks, at which point plants in all treatments were subjected to a final drought period lasting 8 weeks. Plant performance was evaluated by plant biomass and allocation, gas exchange parameters, foliar carbon and nitrogen and stable isotope (δ15N and δ13C) compositions. Plant xylem sap phytohormones were analysed to investigate the effect of microbial inoculation on plant phytohormone profiles and potential relationships with other observed physiological parameters. Across all investigated plant species, inoculation treatments had small effects on plant growth. Further analysis within each species revealed that inoculation treatments did not result in significant biomass gain under well-watered or drought-stressed conditions, and effects on nitrogen nutrition and photosynthesis were variable and minimal. This suggests that the selected commercial microbial inoculant had limited benefits for the tested plant species. Further investigations on the compatibility between the microorganisms (present in the inoculant) and plants, timing of inoculation, viability of the microorganisms and concentration(s) required to achieve effectiveness, under controlled conditions, and field trials are required to test the feasibility and efficacy in actual restoration environments.

Impact of bacterial and fungal inoculants on the resident rhizosphere microbiome and the volatilome of tomato plants under leaf herbivory stress.

Various studies have addressed the impact of microbial inoculants on the composition of the resident microbiome. How microbial inoculants impact plant metabolism and interact with the resident rhizobiota under herbivory stress remains elusive. Here, we investigated the impact of two bacterial and two fungal inoculants, inoculated as single species and as a synthetic community, on the rhizosphere microbiome and volatilome of tomato plants (Solanum lycopersicum) comparing nonstress conditions to exposed to leaf herbivory by Spodoptera exigua. Based on amplicon sequencing analysis, rhizobacterial community composition was significantly affected by all four inoculants and the magnitude of this effect was dependent on herbivory stress. Fungal community composition was altered by the microbial inoculants but independent of herbivory stress. The rhizosphere volatilome was impacted by the microbial inoculation and differences between treatments were evened under herbivory stress. Each microbial inoculant caused unique changes in the volatilome of stressed plants but also shared similar responses, in particular the enhanced production of dimethyl disulfide and benzothiazole. In conclusion, the introduction of microbial inoculants in the tomato rhizosphere caused unique as well as common changes in the rhizosphere microbiome and volatilome, but these changes were minor compared to the microbiome changes induced by herbivory stress.

Long-term microbial community succession and mechanisms of regulation of dissolved organic matter derivation in livestock manure fermentation system.

Industrial-scale aerobic fermentation was conducted with livestock manures. Microbial inoculation promoted the growth of Bacillaceae and consolidated its position as the dominant microorganism. Microbial inoculation substantially influenced dissolved organic matter (DOM) derivation and variations of related components in the fermentation system. The relative abundance of humic acid-like substances of DOM increased from 52.19% to 78.27% in microbial inoculation system, resulting in a high humification level. Moreover, lignocellulose degradation and microbial utilization were the important factors influencing DOM content in fermentation systems. The fermentation system was regulated by microbial inoculation, thus achieving a high level of fermentation maturity.

Integrated application of phosphorus-accumulating bacteria and phosphorus-solubilizing bacteria to achieve sustainable phosphorus management in saline soils.

The challenge of managing agricultural phosphorus (P) in saline regions entails both reducing leaching for environmental protection and maintaining soil available P levels for crop production, which could be achieved through functional microorganisms that can facilitate P transformation processes like P assimilation, inorganic P solubilization, and organic P mineralization. In this study, we proposed an integrated utilization of phosphorus-accumulating bacteria (PAB) and phosphorus-solubilizing bacteria (PSB) to reach the goal of alleviating P leaching while improving soil available P levels. The study conducted a microcosm experiment that combined a soil column test, soil incubation, and pot experiment to evaluate the effect of bacterial inoculants on soil P leaching, soil P availability, and plant P accumulation. The results showed that the application of PAB reduced 22.6 % of dissolved P leaching through the absorption of labile phosphate in the soil, and 17.3 % of particulate P leaching through the promoted soil aggregation. The integrated inoculation of PSB and PAB synergistically improved soil available P content by 18.3 % through the mineralization of soil organic P, and remarkably boosted wheat growth and its P accumulation. Microbial community analysis revealed that the integrated microbial treatment decreased the diversity of soil bacterial community and increased the abundance of native microbial species, i.g. Lysobacter and Ramlibacter, which were positively correlated with soil available P content and alkaline phosphatase level. In conclusion, the integrated microbial strategy based on halotolerant PAB and PSB has great potential for sustainable P management in saline areas and agricultural activities.

Co-inoculation of phosphate-solubilizing bacteria and phosphate accumulating bacteria in phosphorus-enriched composting regulates phosphorus transformation by facilitating polyphosphate formation.

This study aimed to explore the impact of co-inoculating phosphate-solubilizing bacteria (PSB) and phosphate accumulating bacteria (PAB) on phosphorus forms transformation, microbial biomass phosphorus (MBP) and polyphosphate (Poly-P) accumulation, bacterial community composition in composting, using high throughput sequencing, PICRUSt 2, network analysis, structural equation model (SEM) and random forest (RF) analysis. The results demonstrated PSB-PAB co-inoculation (T1) reduced Olsen-P content (1.4 g) but had higher levels of MBP (74.2 mg/kg) and Poly-P (419 A.U.) compared to PSB-only (T0). The mantel test revealed a significantly positive correlation between bacterial diversity and both bioavailable P and MBP. Halocella was identified as a key genus related to Poly-P synthesis by network analysis. SEM and RF analysis showed that pH and bacterial community had the most influence on Poly-P synthesis, and PICRUSt 2 analysis revealed inoculation of PAB increased ppk gene abundance in T1. Thus, PSB-PAB co-inoculation provides a new idea for phosphorus management.