Plant Microbe Research Articles

Plant–microbe interactions explain the surprising recovery of Arctic soil carbon stocks

Plant–microbe interactions explain the surprising recovery of Arctic soil carbon stocks

Arctic soil carbon trajectories shaped by plant–microbe interactions

Arctic soil carbon trajectories shaped by plant–microbe interactions

Mapping, Distribution, Function, and High-Throughput Methodological Strategies for Soil Microbial Communities in the Agroecosystem in the Last Decades

The intricate interplay between SMCs and agroecosystems has garnered substantial attention in recent decades due to its profound implications for agricultural productivity, ecosystem sustainability, and environmental health. Understanding the distribution of SMCs is complemented by investigations into their functional roles within agroecosystems. Soil microbes play pivotal roles in nutrient cycling, organic matter decomposition, disease suppression, and plant‒microbe interactions, profoundly influencing soil fertility, crop productivity, and ecosystem resilience. Elucidating the functional diversity and metabolic potential of SMCs is crucial for designing sustainable agricultural practices that harness the beneficial functions of soil microbes while minimizing detrimental impacts on ecosystem services. Various molecular techniques, such as next-generation sequencing and high-throughput sequencing, have facilitated the elucidation of microbial community structures and dynamics at different spatial scales. These efforts have revealed the influence of factors such as soil type, land management practices, climate, and land use change on microbial community composition and diversity. Advances in high-throughput methodological strategies have revolutionized our ability to characterize SMCs comprehensively and efficiently. These include amplicon sequencing, metagenomics, metatranscriptomics, and metaproteomics, which provide insights into microbial taxonomic composition, functional potential, gene expression, and protein profiles. The integration of multiomics approaches allows for a more holistic understanding of the complex interactions within SMCs and their responses to environmental perturbations. In conclusion, this review highlights the significant progress made in mapping, understanding the distribution, elucidating the functions, and employing high-throughput methodological strategies to study SMCs in agroecosystems.

Isolation and Identification of Tannin-Degrading Bacteria From Goat Feces, Ruminal Fluid, and Rumen Gut

Tannins are toxic polyphenols present in various plants, contributing to microbial attacks and plant protection due to their astringence and bitter taste. However, high tannin inclusion in poultry diets will result in dyspepsia, hampering nutrient absorption and digestion. Interestingly, several bacteria occupying the rumen and gastrointestinal tract (GIT) of animals may tolerate tannins and degrade them by wielding tannase enzymes. The study aims to isolate and characterize potential tannin-degrading bacteria (TDB) from several ruminant specimens. The TDBs were isolated based on their tannin hydrolyzing ability on a minimal salt medium (MSM) agar complemented with 0.2% tannic acid as the sole source of carbon and energy. The maximum tannin tolerance of the isolates was characterized using increased tannin concentrations on the MSM agar plates. Furthermore, the tannase activity was also evaluated over a five-day incubation. A total of 42 tannin degraders were isolated, and 10 TDBs were chosen for further characterization based on the hydrolyzed zone produced. Molecular identification revealed the presence of Bacillus cereus (TDB536), Lysinibacillus macroides (TDB17), Acinetobacter nosocomialis (TDB18, 20, 23, 24, 30, 35), and Staphylococcus saprophyticus (TDB40). TDB17, TDB18, and TDB24 showed the highest tannic acid tolerance at 1.0%, while TDB36 and TDB40 exhibited the lowest tolerance at 0.4%. Each TDB displayed varying tannase activities, ranging from 11.56 to 42.08 U/mL over a five-day incubation period. TDB5 and TDB35 demonstrated significantly higher tannase activity on day 2 (p<0.05). Meanwhile, TDB23 and TDB24 showed the highest tannase on day 4 (p<0.05). Among the isolates, A. nosocomialis strain AE6 (TDB24) from feces exhibited the highest tannase activity (42.08 U/mL) and represented the best TDB. The isolated strains demonstrate their capabilities in reducing tannin's antinutritional effects in poultry feed.

Research Progress in the Joint Remediation of Plants–Microbes–Soil for Heavy Metal-Contaminated Soil in Mining Areas: A Review

Plants growing in heavy metal (HM)-contaminated soil have evolved a special detoxification mechanism. The rhizosphere gathers many living substances and their secretions at the center of plant roots, which has a unique ecological remediation effect. It is of great significance to thoroughly understand the ecological process of rhizosphere pollution under heavy metals (HMs) stress and develop biotechnology for joint remediation using plants and their coexisting microbial systems according to the mechanism of rhizosphere stress. Microbes can weaken the toxicity of HM pollutants by transforming the existing forms or reducing the bioavailability in the rhizosphere. Microbes survive in the HM-polluted soils through the production of stress-resistant substances, the participation of proteins, and the expression of heavy metal resistance genes, which strengthens the resistance of plants. Moreover, microbes can improve the nutritional status of plants to improve plant resistance to HMs. Plants, in turn, provide a habitat for microbes to survive and reproduce, which greatly accelerates the process of bioremediation. Briefly, the combined remediation of soil HMs pollution by plants and microbes is a promising, green, and sustainable strategy. Here, we mainly elucidate the joint remediation mechanism of plant–microbe symbiosis and introduce the coping characteristics of plants, microbes, and their symbiotic system, hoping to provide a scientific basis for the remediation of HM-contaminated soil in mining areas and the sustainable development of the ecological environment.

Testing microbial pest control products in bees, a comparative study on different bee species and their interaction with two representative microorganisms

BackgroundThe evaluation of the impact of pesticides on non-target species, like bees, is a crucial factor in registration procedures. Therefore, standardized test procedures have been developed on OECD level assessing the effects of chemicals on honey bees or bumble bees. Unfortunately, these protocols cannot directly be adapted for testing products that contain microorganisms. Interest in the use of microorganisms has increased in recent years due to their specificity to target species while not harming non-target organisms. This study aimed to evaluate optimal conditions to assess the effects of microbial plant protection products on bee species according to currently available test protocols. Some of the most commonly used microorganisms for plant protection, Bacillus thuringiensis subspecies aizawai (B. t. a. ABTS 1857) and Beauveria bassiana (B. b. ATCC 74040) were tested on Apis mellifera, Bombus terrestris, and Osmia bicornis at different temperatures (18, 26, 33 °C) under laboratory conditions.ResultsExposure to the product containing B. t. a. ABTS 1857 resulted in higher mortality compared to B. b. ATCC 74040 in all tested bee species. A temperature-dependent effect towards higher mortality at higher temperatures of 26 °C or 33 °C was observed in O. bicornis exposed to both microorganisms. A. mellifera showed variable responses, but for B. terrestris there was mostly no effect of temperature when exposed to microorganisms in high concentrations. However, temperature affected longevity of bee species in the non-exposed control group. A. mellifera mortality increased with decreasing temperatures, while B. terrestris and O. bicornis mortality increased with increasing temperatures. A test duration of 15 or 20 days was found to be suitable for testing these microorganisms.ConclusionIn conclusion, 26 °C should be considered the worst-case scenario for testing B. bassiana on all tested bee species. For testing B. thuringiensis, a temperature of 33 °C is recommended for A. mellifera, whereas B. terrestris and O. bicornis should be tested at 26 °C.

Effects of Microbial Biostimulants on Maize and Its Pest, the Western Corn Rootworm, Diabrotica virgifera virgifera

The western corn rootworm, Diabrotica virgifera virgifera, (Coleoptera: Chrysomelidae) is a serious pest of maize in the USA and Europe. Microbial plant biostimulants such as bacteria, fungi, and algae are designed to stimulate plant nutrition and growth, with some hypothesized to also possess insecticidal properties. We tested 10 biostimulants (four bacteria, five fungi, and one alga) under laboratory and greenhouse conditions. Most biostimulants did not affect the eggs, larvae, or adults of D.v. virgifera. However, in the laboratory, 10% of biostimulants improved egg hatching, and 40% killed some larvae, including the fungi Beauveria bassiana, Rhizophagus irregularis, and Trichoderma asperellum, and the bacterium Ensifer meliloti. Under potted-plant conditions in the greenhouse, these insecticidal effects were not detectable. However, several biostimulants slightly increased height and shoot length of uninfested maize plants, but reduced volume and length of their roots as well as above-ground biomass. Interestingly, 30% of the biostimulants enhanced the plant’s defence against larvae, for example, Bacillus amyloliquefaciens, B. subtilis, and E. meliloti. These may warrant further research into their modes of action as well as field trials to better understand and optimize their potential use in sustainable and integrated pest management.

An innovative soil mesocosm system for studying the effect of soil moisture and background NO on soil surface C and N trace gas fluxes

Nitric oxide (NO) is a key substance in atmospheric chemistry, influencing the formation and destruction of tropospheric ozone and the atmosphere's oxidizing capacity. It also affects the physiological functions of organisms. NO is produced, consumed, and emitted by soils, the effects of soil NO concentrations on microbial C and N cycling and associated trace gas fluxes remain largely unclear. This study describes a new automated 12-chamber soil mesocosm system that dynamically changes incoming airflow composition. It was used to investigate how varying NO concentrations affect soil microbial C and N cycling and associated trace gas fluxes under different moisture conditions (30% and 50% WFPS). Based on detection limits for NO, NO2, N2O, and CH4 fluxes of < 0.5 µg N or C m−2 h−1 and for CO2 fluxes of < 1.2 mg C m−2 h−1, we found that soil CO2, CH4, NO, NO2, and N2O were significantly affected by different soil moisture levels. After 17 days cumulative fluxes at 50% WFPS increased by 40, 400, and 500% for CO2, N2O, and CH4, respectively, when compared to 30% WFPS. However, cumulative fluxes for NO, and NO2, decreased by 70, and 40%, respectively, at 50% WFPS when compared to 30% WFPS. Different NO concentrations tended to decrease soil C and N fluxes by about 10–20%. However, with the observed variability among individual soil mesocosms and minor fluxes change. In conclusion, the developed system effectively investigates how and to what extent soil NO concentrations affect soil processes and potential plant–microbe interactions in the rhizosphere.

Seasonal dynamics of carbon, nitrogen, and phosphorus stoichiometric traits in an extensive green roof in Nanjing, China

Green roofs (GRs) are vital for shaping the material cycles of urban ecosystems as a form of distributed green infrastructure. However, current studies have predominantly focused on the material exchange between GRs and the urban environment, neglecting the internal distribution and equilibrium of constituent elements. By monitoring carbon (C), nitrogen (N), and phosphorus (P) in Sedum lineare Thunb and four substrates throughout the seasons, this study analyzes the ecological stoichiometric characteristics of an extensive GR in Nanjing, China. Intra-annual ratios of C:N (46.02, 13.38, 15.40), C:P (252.41, 57.85, 47.22), and N:P (5.75, 4.23, 3.84) were identified in the plant, substrate, and substrate microbial biomass, respectively. The intra-annual ratios of plant to substrate C, N, and P were roughly 9:1, 7:3, and 6:4, respectively. The use of different substrates resulted in significant variations in plant C, N, and P levels and their quantitative ratios, leading to distribution differences of these elements. Furthermore, substrate C, N, and P levels exhibit a generalized threshold effect on microbial biomass and plant C, N, and P concentrations. Notably, the substrate demonstrates an organic C sink potential of 7.11 g/kg/season, surpassing that of plants in unit mass. These findings contribute to understanding the distribution and dynamics of C, N, and P elements within extensive GRs.

The Greening of One Health: Plants, Pathogens, and the Environment.

One Health has an aspirational goal of ensuring the health of humans, animals, plants, and the environment through transdisciplinary, collaborative research. At its essence, One Health addresses the human clash with Nature by formulating strategies to repair and restore a (globally) perturbed ecosystem. A more nuanced evaluation of humankind's impact on the environment (Nature, Earth, Gaia) would fully intercalate plants, plant pathogens, and beneficial plant microbes into One Health. Here, several examples point out how plants and plant microbes are keystones of One Health. Meaningful cross-pollination between plant, animal, and human health practitioners can drive discovery and application of innovative tools to address the many complex problems within the One Health framework.

The rhizobacterial Priestia megaterium strain SH-19 mitigates the hazardous effects of heat stress via an endogenous secondary metabolite elucidation network and molecular regulation signalling

Global warming is a leading environmental stress that reduces plant productivity worldwide. Several beneficial microorganisms reduce stress; however, the mechanism by which plant–microbe interactions occur and reduce stress remains to be fully elucidated. The aim of the present study was to elucidate the mutualistic interaction between the plant growth-promoting rhizobacterial strain SH-19 and soybeans of the Pungsannamul variety. The results showed that SH-19 possessed several plant growth-promoting traits, such as the production of indole-3-acetic acid, siderophore, and exopolysaccharide, and had the capacity for phosphate solubilisation. The heat tolerance assay showed that SH-19 could withstand temperatures up to 45 °C. The strain SH-19 was identified as P. megaterium using the 16S ribosomal DNA gene sequence technique. Inoculation of soybeans with SH-19 improved seedling characteristics under high-temperature stress. This may be due to an increase in the endogenous salicylic acid level and a decrease in the abscisic acid level compared with the negative control group. The strain of SH-19 increased the activity of the endogenous antioxidant defense system, resulting in the upregulation of GSH (44.8%), SOD (23.1%), APX (11%), and CAT (52.6%). Furthermore, this study involved the transcription factors GmHSP, GmbZIP1, and GmNCED3. The findings showed upregulation of the two transcription factors GmbZIP1 (17%), GmNCED3 (15%) involved in ABA biosynthesis and induced stomatal regulation, similarly, a downregulation of the expression pattern of GmHSP by 25% was observed. Overall, the results of this study indicate that the strain SH-19 promotes plant growth, reduces high-temperature stress, and improves physiological parameters by regulating endogenous phytohormones, the antioxidant defense system, and genetic expression. The isolated strain (SH-19) could be commercialized as a biofertilizer.

Plant Microbe Interactions an Implications for Sustainable Agriculture

Plant-microbe interactions are vital to the health and productivity of agricultural systems, influencing plant growth, nutrient uptake, and stress resistance. These interactions involve a diverse range of microorganisms, including bacteria, fungi, and viruses. Symbiotic relationships, such as those between legumes and rhizobia or mycorrhizal fungi and plant roots, enhance nutrient availability and plant growth—commensal interactions with endophytic microbes further support plant health by producing growth-promoting substances and offering protection against pathogens. However, pathogenic interactions pose significant challenges, necessitating a deep understanding of plant immune responses and microbial pathogenicity. This review explores the intricate mechanisms underlying plant-microbe interactions, focusing on the complex signaling pathways and molecular dialogues facilitating these relationships. It highlights the benefits of these interactions, such as improved nutrient cycling, enhanced plant growth, and increased resilience to biotic and abiotic stresses. It underscores their potential to revolutionize sustainable agriculture. Practical applications are examined through case studies, demonstrating the successful integration of beneficial microbes into farming practices and the development of commercial microbial inoculants. Despite their promise, implementing plant-microbe interactions in agriculture faces challenges, including field variability, crop compatibility issues, and environmental concerns related to introducing non-native microbes. Addressing these challenges requires a multidisciplinary approach, combining genomics, biotechnology, and sustainable management practices. Continued research is essential to harness these interactions effectively, aiming to enhance crop productivity, reduce chemical inputs, and promote environmental health, thereby contributing to a more resilient and sustainable food production system.

Developing Practical Strategies for Long-Term Storage of Compost Tea: The Role of Molybdate and Nitrate in Maintaining Microbial Activity and Plant Benefits

Developing Practical Strategies for Long-Term Storage of Compost Tea: The Role of Molybdate and Nitrate in Maintaining Microbial Activity and Plant Benefits

Potential uses of botanical extracts of Larrea and Grindelia in organic agriculture: Effects on soil properties and functional traits relative to growth

Biostimulants—including botanical extracts—are natural preparations that have no negative effects on environmental health or populations and improve soil health and plant growth. Our objective was to evaluate the use of botanical extracts from two native species of the Patagonian Monte, an infusion of Larrea nitida (5%-L5 and 10%-L10) and a ferment of Grindelia chiloensis (5%-G5 and 10%-G10), on soil properties and the growth of a model plant (Triticum aestivum). While the 5% and 10% Grindelia ferments increased microbial respiration, soil N and C content, and biomass production, the 10% Larrea infusion inhibited microbial respiration and decreased total biomass. The Grindelia ferment has potential for use as a biostimulant in agroecological production, whereas the Larrea infusion does not show potential for such use. The inhibitory effect of phenolic compounds on microbial activity and plant growth should be addressed in future studies.

Implications of Domestication in Theobroma cacao L. Seed-Borne Microbial Endophytes Diversity

The study of plant–microbe interactions is a rapidly growing research field, with increasing attention to the role of seed-borne microbial endophytes in protecting the plant during its development from abiotic and biotic stresses. Recent evidence suggests that seed microbiota is crucial in establishing the plant microbial community, affecting its composition and structure, and influencing plant physiology and ecology. For Theobroma cacao L., the diversity and composition of vertically transmitted microbes have yet to be addressed in detail. We explored the composition and diversity of seed-borne endophytes in cacao pods of commercial genotypes (ICS95, IMC67), recently liberated genotypes from AGROSAVIA (TCS01, TCS19), and landraces from Tumaco (Colombia) (AC9, ROS1, ROS2), to evaluate microbial vertical transmission and establishment in various tissues during plant development. We observed a higher abundance of Pseudomonas and Pantoea genera in the landraces and AGROSAVIA genotypes, while the commercial genotypes presented a higher number of bacteria species but in low abundance. In addition, all the genotypes and plant tissues showed a high percentage of fungi of the genus Penicillium. These results indicate that domestication in cacao has increased bacterial endophyte diversity but has reduced their abundance. We isolated some of these seed-borne endophytes to evaluate their potential as growth promoters and found that Bacillus, Pantoea, and Pseudomonas strains presented high production of indole acetic acid and ACC deaminase activity. Our results suggest that cacao domestication could lead to the loss of essential bacteria for seedling establishment and development. This study improves our understanding of the relationship and interaction between perennial plants and seed-borne microbiota.

Mycorrhizal inoculation alters rhizosphere fungal community and root morphology to improve drought tolerance of resource-acquisitive but not resource-conservative Quercus species

The mutualistic association between mycorrhizal fungi and plants is well known to improve plant drought resistance. However, the influence of external inoculants on the interactions between soil microbial communities and plant functional traits and how these interactions improve plant drought tolerance under drought stress remain unclear. We conducted a pot inoculation experiment to assess the effect of two inoculated fungal strains (Clitopolius hobsonii NL-19 and C. sp. HSL-YX-7-A) on morphological traits and rhizosphere fungal communities of eight Quercus species seedlings. Plant and soil fungal traits were measured 2 months after inoculation and then underwent a short-term (33 days) drought rewetting treatment. The biomass of all tree species reduced significantly under drought stress followed by rewetting (drought treatment) compared with that in the control treatment (well-watered); however, inoculated mycorrhizal fungi (drought + mycorrhizal inoculation treatment) increased the biomass of five Quercus species (growth-promoting species (GPS) exhibiting a significant increase in biomass under mycorrhizal inoculation treatment than under the uninoculated treatment during drought stress, characterized by a resource-use acquisitive strategy) and had no effect on the other three Quercus species (non-growth-promoting species (NGPS) exhibiting no significant difference in biomass between mycorrhizal inoculation and uninoculated treatments during drought stress, characterized by a resource-use conservative strategy). The leaf traits of the two species groups (GPS and NGPS) varied little among the three treatments. The values of most root traits (e.g., specific root length and root length) of GPS increased significantly under drought and drought + mycorrhizal inoculation treatments compared with those in the control, whereas relatively minor variations were observed in NGPS among the three treatments. The fungal community composition and functional groups (primary trophic modes) in the drought treatment were altered for NGPS but not for GPS; additionally, they changed in the drought + mycorrhizal inoculation treatment for GPS but not for NGPS when compared with those in the drought treatment. Furthermore, the drought tolerance of GPS was improved directly by fungal functional groups (i.e., Pathotroph-Saprotroph- Symbiotrophs proliferation) and indirectly by root traits (e.g., increased specific root length), whereas NGPS may adapt to drought stress through other pathways (e.g., physiological and biochemical regulation). Overall, drought and mycorrhizal inoculation affected the root traits and fungal community structure of Quercus seedlings, which rely on plant resource-use strategies. Our results provide new insights into the relationship between plant resource-use strategies and soil microbes for improving plant performance under drought stress.

Dual PGPR-AMF Inoculation Offsets Salinity Stress Impact on the Fodder Halophyte Sulla carnosa by Concomitantly Modulating Plant ABA Content and Leaf Antioxidant Response

AbstractSalt-tolerant microbes are known to mitigate various biotic and abiotic stresses in plants. However, the intimate mechanisms involved, as well as their effects on the production of signaling molecules associated with the host plant–microbe interaction remain largely unknown. The present work aimed to investigate the role and potential uses of arbuscular mycorrhizal fungi (AMF) Rhizophagus intraradices and/or halotolerant plant growth-promoting rhizobacteria (PGPR) Bacillus subtilis in improving plant growth, functional biochemical synthesis and signaling of endogenous abscisic acid during plant response to short- and long-term salt stress in the forage halophyte Sulla carnosa. Plant growth attributes and biochemical traits were determined at 2 different time intervals (45 and 60 d after transplanting time) when salinity was raised from 100 to 200 mM NaCl. S. carnosa showed significant reduction in dry biomass in response to NaCl stress at the second harvest (200 mM NaCl); however inoculating plants with B. subtilis alone or associated with R. intraradices offset salt impact. Leaf electrolyte leakage was significantly increased by salinity but was significantly reduced following dual microbial inoculation. The applied bacterial inoculants also mitigated oxidative stress as reflected by the higher activities of catalase (APX) and superoxide dismutase (SOD) antioxidant enzymes and reduced H2O2 level. Inoculation with B. subtilis and R. intraradices upregulated 9-cisepoxycarotenoid dioxygenase 1 (NCED1) and SOD genes expression in S. carnosa plants upon salinity treatment. Furthermore, dual AMF-PGPR -inoculated plants accumulated significantly higher levels of abscisic acid (ABA) in both leaves and roots than non-inoculated and single inoculated plants under salinity stress at both harvest times, thereby accounting for their higher salt tolerance of salt-challenged S. carnosa plants. As a whole, the use of halophytic plants associated with beneficial soil microorganisms could improve the effectiveness of biological methods for saline soil rehabilitation. At the mechanistic level, ABA might represent a key player in the attenuation of salt impact in inoculated plants.

Plant–microbe interactions underpin contrasting enzymatic responses to wetland drainage

Plant–microbe interactions underpin contrasting enzymatic responses to wetland drainage

Fractions of soil phosphorus mediated by rhizospheric phoD‐harbouring bacteria of deep‐rooted desert species are determined by fine‐root traits

Abstract Soil phosphorus (P) availability is a crucial factor determining primary productivity in terrestrial ecosystem. Plant functional traits and microbes under P‐deficient conditions can respond positively to increase soil P bioavailability. Whether and/or how the fine‐root traits (FRTs) of deep‐rooted desert species affect the rhizosphere and bulk soil community of phoD‐harbouring bacteria and thus improve the availability of soil P, however, remains unclear. We conducted a three‐year artificial outdoor pot experiment of P supply using Alhagi sparsifolia Shap. (hereafter Alhagi) to address this gap. Fine‐root samples from 1‐ and 3‐year‐old Alhagi seedlings and samples of the rhizospheres and bulk soil were collected. High‐throughput sequencing, sequential extraction and root system scanning were used to determine soil phoD‐harbouring bacteria community, Hedley‐P fractions and the FRTs. Fine‐root surface area (RSA), specific root length, foliar Mn concentration (indicating the quantities of root carboxylates that are released) and acid phosphatase (APase) activity were significantly higher in the no‐P supply compared with the high‐P supply conditions. APase activity was significantly higher by 27%, but the foliar Mn concentration was remarkably lower by 26%, in the 3‐ than the 1‐year‐old seedlings. The rhizospheric concentrations of labile P, moderately labile P, inorganic P and organic P in the no‐P supply condition were 5%, 11%, 10% and 21% higher, respectively, in the 3‐ than the 1‐year‐old seedlings. RSA and the foliar Mn concentration were dominated root predictors for the rhizospheric phoD‐harbouring bacteria community for the 1‐year‐old seedlings, whereas fine‐root P concentration was the dominated root predictor for the rhizospheric and bulk soil phoD‐harbouring bacteria communities for the 3‐year‐old seedlings. Soil water content, as the most dominant soil factor driving the variation of phoD‐harbouring bacteria community, notably could not be ignored. FRTs were the main factors that directly and positively determined rhizospheric phoD‐harbouring bacteria community and thus influenced soil P availability, but bulk soil phoD‐harbouring bacteria community were dominated by inorganic P concentration. The importance of fine‐root morphological traits to soil P availability gradually increased as the plants grew. Overall, our results emphasize the significance of rhizospheric phoD‐harbouring bacteria determined by the effect of FRTs on the bioavailability of soil P. Read the free Plain Language Summary for this article on the Journal blog.

Specific root length regulated the rhizosphere effect on denitrification across distinct macrophytes

Macrophytes influence nitrogen (N) removal from wetlands. However, the specific plant traits responsible for this effect and the related microbial mechanisms remain largely unknown, especially root traits. In a mesocosm experiment, we determined the rhizosphere effect (RE) on microbial N removal processes by incubating rhizosphere and bulk soils collected from 11 macrophyte species. In addition, we examined root traits (involved in chemistry and morphology), along with examining the diversity, compositions, and abundance of bacterial communities involved in denitrification (nirS and nirK) and anammox (hzsB). Across the 11 macrophyte species, the positive RE on denitrification ranged from 66% to 412%, with an average of 194.72%. RE on denitrification was significantly and positively correlated with the recruitment of nir-type denitrifiers in the rhizosphere. We found that higher specific root length (SRL) root promoted the stronger RE, by increasing the abundance of nir-type denitrifiers and further enhancing N removal. Net N removal from water in the wetlands increased with a higher positive RE on nir-type denitrifiers. In addition, SRL significantly influenced the compositions of denitrifiers in the rhizosphere soil. We further found that the enrichment of Azospira, Bradyrhizobium, Sinorhizobium, Rhodopseudomonas, Alcaligenaceae, Bradyrhizobiaceae, and Pleomorphomonas improved the denitrification rate. These findings highlight the potential of root morphology in regulating plant–microbe interactions, thereby improving water purification.