Abundance Of Microbial Genes Research Articles

Unravelling the Role of Rumen Microbial Communities, Genes, and Activities on Milk Fatty Acid Profile Using a Combination of Omics Approaches.

Milk products are an important component of human diets, with beneficial effects for human health, but also one of the major sources of nutritionally undesirable saturated fatty acids (SFA). Recent discoveries showing the importance of the rumen microbiome on dairy cattle health, metabolism and performance highlight that milk composition, and potentially milk SFA content, may also be associated with microorganisms, their genes and their activities. Understanding these mechanisms can be used for the development of cost-effective strategies for the production of milk with less SFA. This work aimed to compare the rumen microbiome between cows producing milk with contrasting FA profile and identify potentially responsible metabolic-related microbial mechanisms. Forty eight Holstein dairy cows were fed the same total mixed ration under the same housing conditions. Milk and rumen fluid samples were collected from all cows for the analysis of fatty acid profiles (by gas chromatography), the abundances of rumen microbiome communities and genes (by whole-genome-shotgun metagenomics), and rumen metabolome (using 500 MHz nuclear magnetic resonance). The following groups: (i) 24 High-SFA (66.9–74.4% total FA) vs. 24 Low-SFA (60.2–66.6%% total FA) cows, and (ii) 8 extreme High-SFA (69.9–74.4% total FA) vs. 8 extreme Low-SFA (60.2–64.0% total FA) were compared. Rumen of cows producing milk with more SFA were characterized by higher abundances of the lactic acid bacteria Lactobacillus, Leuconostoc, and Weissella, the acetogenic Proteobacteria Acetobacter and Kozakia, Mycobacterium, two fungi (Cutaneotrichosporon and Cyphellophora), and at a lesser extent Methanobrevibacter and the protist Nannochloropsis. Cows carrying genes correlated with milk FA also had higher concentrations of butyrate, propionate and tyrosine and lower concentrations of xanthine and hypoxanthine in the rumen. Abundances of rumen microbial genes were able to explain between 76 and 94% on the variation of the most abundant milk FA. Metagenomics and metabolomics analyses highlighted that cows producing milk with contrasting FA profile under the same diet, also differ in their rumen metabolic activities in relation to adaptation to reduced rumen pH, carbohydrate fermentation, and protein synthesis and metabolism.

Effect of biomass immobilization and reduced graphene oxide on the microbial community changes and nitrogen removal at low temperatures

The slow growth rate and high optimal temperatures for the anaerobic ammonium oxidation (anammox) bacteria are significant limitations of the anammox processes application in the treatment of mainstream of wastewater entering wastewater treatment plant (WWTP). In this study, we investigate the nitrogen removal and microbial community changes in sodium alginate (SA) and sodium alginate–reduced graphene oxide (SA-RGO) carriers, depending on the process temperature, with a particular emphasis on the temperature close to the mainstream of wastewater entering the WWTP. The RGO addition to the SA matrix causes suppression of the beads swelling, which intern modifies the mechanical properties of the gel beads. The effect of the temperature drop on the nitrogen removal rate was reduced for biomass entrapped in SA and SA-RGO gel beads in comparison to non-immobilized biomass, this suggests a ‘‘protective” effect caused by immobilization. However, analyses performed using next-generation sequencing (NGS) and qPCR revealed that the microbial community composition and relative gene abundance changed significantly, after the implementation of the new process conditions. The microbial community inside the gel beads was completely remodelled, in comparison with inoculum, and denitrification contributed to the nitrogen transformation inside the beads.

Coffee waste as an eco-friendly and low-cost alternative for biochar production impacts on sandy soil chemical attributes and microbial gene abundance

Biochar is a material produced by the pyrolysis of agro-industrial waste, which has become one of the most promising management tools to improve soil quality. The aim was to determine the effects of incorporating biochar from different coffee wastes in sandy soil, cropped with maize, on soil chemical and microbial attributes. The experiment followed a factorial design 2 × 3 + 1 with two types of biochar, including coffee ground (CG) or coffee husk (CH) in 3 doses (4, 8, and 16 t·ha-1) and a control fertilized solely with bovine manure (3 t·ha-1). The variables analyzed were soil organic carbon, chemical attributes, microbial biomass (C, N and P), soil basal respiration and microbial gene abundance (16S rRNA, 18S rRNA and nifH gene). Most chemical attributes were strongly increased by CH application, while CG at 8 t·ha-1 increased the soil C:N ratio (3.5 times), P (2.1 times) and K+ (7.9 times) and at 4 t·ha-1 increased the C content, microbial biomass C and N (3, 2.1 and 1.6 times, respectively). The application of CG biochar at 16 t·ha-1 showed trend to increase the abundance of bacteria, fungi and diazotrophic genes (11, 10 and 2%, respectively). Contribution of both coffee biochar types, but mainly CH, was more effective than the soil that received organic manure alone. Biochar from coffee wastes is a promising tool to improve sandy soil quality.

Dissimilatory nitrate ammonification and N2 fixation helps maintain nitrogen nutrition in resource-limited rice paddies

Un-fertilized rice paddies have shown maintained soil nitrogen (N) status, stable N supply to the rice plant and sustained rice yields at moderate levels for hundreds of years. Microbial N2 fixation is known to contribute N to un-fertilized paddies, but it cannot fully explain the maintained N nutrition, where favourable conditions exist for N loss by denitrification. We used 15N tracer, 15N2 uptake, acetylene reduction assay and qPCR to simultaneously investigate N2 fixation, dissimilatory nitrate reduction to ammonium (DNRA), denitrification and related microbial gene abundances in long-term low (or no) and high N input rice paddies of Myanmar. We also determined how varying soil organic carbon-to-nitrate (SOC/NO3−) ratios affect nitrate partitioning between DNRA and denitrification by manipulating these ratios through labile organic carbon addition. We observed more than 2.5 times higher N2 fixation (1.49–2.08 μg N g−1 soil day−1) and significantly higher N2 fixing gene (nifH) abundance in low compared with high N input paddies. Up to 60% of the soil nitrate (1.51–2.67 μg NO3−-N g−1 soil day−1) was ammonified through DNRA, and only 15% was lost as N2 through denitrification in low N input paddies, whereas denitrification exceeded DNRA in high N input paddies. The microbial gene related to DNRA activity (nrfA) was also higher in low input than in high input rice paddies. We found that nitrate retention can be improved in high N input rice paddies by maintaining a higher soil organic carbon-to-nitrate ratio. Our findings highlight the unique microbial N-cycling strategies in resource-limited paddies which support maintained N nutrition of the paddy system.

Soil microbial community restructuring and functional changes in ancient kauri (Agathis australis) forests impacted by the invasive pathogen Phytophthora agathidicida

New Zealand's culturally iconic, ancient kauri (Agathis australis) forests are threatened with extinction as a result of dieback caused by an invasive and highly virulent soil-borne pathogen (Phytophthora agathidicida). Kauri trees function as a foundation species in their forests, supporting an ecologically distinct plant and soil environment. The impacts of disease outbreak and subsequent tree dieback on kauri forest ecosystems, in particular soil microbial communities, remains unknown. Using high throughput amplicon sequencing and GeoChip 5 S microarray analysis we analysed the differences in diversity, taxonomic composition and functional genes related to C and N cycling of soil microbial communities associated with asymptomatic and symptomatic mature kauri. Our results found significant differences in the fungal diversity and both fungal and bacterial community composition between asymptomatic and symptomatic kauri. Several microbial taxa known in the literature for their roles in disease suppression, such as Penicillium, Trichoderma, Enterobacteriacae and Pseudomonas, were identified as being significantly higher in asymptomatic kauri soils. These findings have provided a promising direction for the discovery of disease suppressive microbial taxa against kauri dieback. In addition, the composition and abundances of microbial genes related to C and N cycling also differed significantly. These findings highlight the potential long term impacts that dieback disease may have on the health and functioning of kauri forests.

Abstract 5734: Gut microbiota predicts response and toxicity with neoadjuvant immunotherapy

Abstract Introduction: Checkpoint blockade immunotherapy has revolutionized melanoma treatment. However, immune related adverse events (irAEs) are frequent, particularly when PD-1 and CTLA-4 blocking antibodies are combined. There is an urgent need for biomarkers to predict response as well as toxicity. The intestinal microbiome influences immune processes throughout the body and is therefore hypothesised to influence both immunotherapy response and well as development of irAEs. Methods: This study utilized sequencing to profile the fecal microbiome from Stage III melanoma patients (n= 38) treated with combination anti-PD1 and anti-CTLA4 antibodies in the neoadjuvant setting (OpacinNeo Trial; NCT02977052) at Melanoma Institute Australia. Absolute bacterial loads were determined with qPCR. Global microbial gene abundance was determined through metagenomic sequencing, allowing analysis of microbial metabolic capcity, and actual short chain fatty acid output (butyrate, acetate, propionate) was assessed by NMR. Matched PBMC were profiled in detail using mass cytometry and immune populations were correlated with microbial metrics. We tested the ability of machine learning to predict therapeutic response and irAEs from microbial data. Results: Patients who failed to respond (n=6), and those who developed severe (G3-G5) irAEs (n=11), had low microbial diversity before treatment (p=0.0234 and p=0.0226 respectively). Four of the six non-responders in this cohort failed to complete treatment and received immunosuppression before pathologic assessment of response, because of the development of severe irAEs. Thus, non-response may, in fact, have been a consequence of irAE development in those cases. High pre-treatment loads of Ruminococcaceae and methanogenic archaea, and greater relative abundance of butyrate production pathways, were significantly associated with response and protection from irAEs. Patients who had low bacterial diversity had increased proportions of effector and memory CD4 and CD8 T cells in the blood and increased numbers of circulating MAIT, NK and gdT cells prior to immunotherapy. Importantly, microbial taxa were predictive of patients who subsequently failed to respond to therapy while also developing severe irAEs with overall accuracy of 92.1%. Conclusions: A gut ecosystem enriched with beneficial microbial functions including production of butyrate is associated with protection from irAEs with neoadjuvant combination immunotherapy. The findings allow prediction of outcomes with combination immunotherapy and will inform development of therapeutic microbial interventions. Citation Format: Marcel Batten, Erin Shanahan, Rebecca Simpson, Mark Read, Ines P. Silva, Alexandra Angelatos, Jian Tan, Chandra Adhikari, Alexander M. Menzies, Robyn P. Saw, Laurence Macia, Maria Gonzalez, Kerwin Shannon, Rebecca Velickovic, Irene L. Reijers, Christian U. Blank, James S. Wilmott, Andrew J. Holmes, Richard A. Scolyer, Georgina V. Long. Gut microbiota predicts response and toxicity with neoadjuvant immunotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5734.

Differential impacts of nitrogen addition on rhizosphere and bulk‐soil carbon sequestration in an alpine shrubland

Abstract Due to complex root–soil interactions, the responses of carbon (C) dynamics in the rhizosphere to elevated nitrogen (N) deposition may be different from those in bulk soil. However, the potentially different response of C dynamics in the rhizosphere and bulk soils and their contributions to soil C sequestration under N deposition is still not elucidated. We conducted an N addition experiment in an alpine shrubland dominated by Sibiraea angustata located on the eastern Qinghai‐Tibet Plateau (QTP). We measured the soil organic C (SOC) contents and density fractions in the rhizosphere and bulk soils in the top 15 cm of mineral soil and then employed a numerical model based on the rhizosphere extent to evaluate how the rhizosphere modulates soil C sequestration under N addition. We also measured the microbial gene abundance and C‐acquisition enzyme activities to assess microbial community responses to N addition. The results showed that nitrogen addition had opposite effects on the rhizosphere and bulk‐soil C stocks. Specifically, N addition decreased the rhizosphere SOC content by increasing bacterial abundance, β‐glucosidase activity, and thus accelerating the loss of free light fraction C (FLF‐C). However, N addition increased the bulk‐soil C content, which was corresponding with the reduced oxidase activities and the accelerated accumulation of heavy fraction C (HF‐C) under N addition. Numerical model analysis showed that the decrease induced by N addition in rhizosphere SOC stock ranged from 0.11 to 3.01 kg C/m2 as root exudation diffusion distance extended from 0.5 to 2 mm, while the corresponding increase in the bulk‐soil C stock ranged from 1.91 to 4.08 kg C/m2. By synthesizing the dynamics of the SOC stocks in these two soil compartments under N addition, the SOC stock at the ecosystem level exhibited an increase in range of 0.73–2.44 kg C/m2. Synthesis. Our results suggest that alpine shrublands on the eastern QTP have great potential for soil C sequestration under N deposition, and the magnitude of the sequestration would depend closely on the responses of rhizosphere microbial C processes and the rhizosphere extent. Our results highlight the importance of integrating rhizosphere processes into land surface models to accurately predict ecosystem functions in the background of elevated N deposition.

Nitrous oxide production from soybean and maize under the influence of weedicides and zero tillage conservation agriculture

Current experiment envisages evaluating N2O production from nitrification and denitrification under the influence of weedicides, cropping systems and conservation agriculture (CA). The weed control treatments were conventional hand weeding (no weedicide), pre emergence weedicide pendimethalin and post emergence weedicide imazethapyr for soybean, atrazine for maize. Experiment was laid out in randomized block design with three replicates. Soils were collected from different depths and incubated at different moisture holding capacity (MHC). N2O production from nitrification varied from 2.77 to 6.04 ng N2O g−1 soil d−1 and from denitrification varied from 0.05 to 1.34 ng N2O g−1 soil d−1. Potential nitrification rate (0.16–0.39 mM NO3 produced g−1 soil d−1) was higher than potential denitrification rate (0.45–0.93 mM NO3 reduced g−1 soil d−1). N2O production, nitrification, denitrification, and microbial gene abundance were higher in maize than soybean. Both N2O production and nitrification decreased (p < 0.05) with soil depth, while denitrification increased (p < 0.05) with soil depth. Abundance of eubacteria and ammonia oxidizing bacteria (AOB) were high (p < 0.01) at upper soil layer and declined with depth. Abundance of ammonia oxidizing archaea (AOA) increased (p < 0.05) with soil depth. Study concludes that intensive use of weedicides in CA may stimulate N2O production.

High-resolution temporal profiling of the human gut microbiome reveals consistent and cascading alterations in response to dietary glycans

BackgroundDietary glycans, widely used as food ingredients and not directly digested by humans, are of intense interest for their beneficial roles in human health through shaping the microbiome. Characterizing the consistency and temporal responses of the gut microbiome to glycans is critical for rationally developing and deploying these compounds as therapeutics.MethodsWe investigated the effect of two chemically distinct glycans (fructooligosaccharides and polydextrose) through three clinical studies conducted with 80 healthy volunteers. Stool samples, collected at dense temporal resolution (~ 4 times per week over 10 weeks) and analyzed using shotgun metagenomic sequencing, enabled detailed characterization of participants’ microbiomes. For analyzing the microbiome time-series data, we developed MC-TIMME2 (Microbial Counts Trajectories Infinite Mixture Model Engine 2.0), a purpose-built computational tool based on nonparametric Bayesian methods that infer temporal patterns induced by perturbations and groups of microbes sharing these patterns.ResultsOverall microbiome structure as well as individual taxa showed rapid, consistent, and durable alterations across participants, regardless of compound dose or the order in which glycans were consumed. Significant changes also occurred in the abundances of microbial carbohydrate utilization genes in response to polydextrose, but not in response to fructooligosaccharides. Using MC-TIMME2, we produced detailed, high-resolution temporal maps of the microbiota in response to glycans within and across microbiomes.ConclusionsOur findings indicate that dietary glycans cause reproducible, dynamic, and differential alterations to the community structure of the human microbiome.

Changes of the human skin microbiota upon chronic exposure to polycyclic aromatic hydrocarbon pollutants

BackgroundPolycyclic aromatic hydrocarbons (PAHs) are of environmental and public health concerns and contribute to adverse skin attributes such as premature skin aging and pigmentary disorder. However, little information is available on the potential roles of chronic urban PAH pollutant exposure on the cutaneous microbiota. Given the roles of the skin microbiota have on healthy and undesirable skin phenotypes and the relationships between PAHs and skin properties, we hypothesize that exposure of PAHs may be associated with changes in the cutaneous microbiota. In this study, the skin microbiota of over two hundred Chinese individuals from two cities in China with varying exposure levels of PAHs were characterized by bacterial and fungal amplicon and shotgun metagenomics sequencing.ResultsSkin site and city were strong parameters in changing microbial communities and their assembly processes. Reductions of bacterial-fungal microbial network structural integrity and stability were associated with skin conditions (acne and dandruff). Multivariate analysis revealed associations between abundances of Propionibacterium and Malassezia with host properties and pollutant exposure levels. Shannon diversity increase was correlated to exposure levels of PAHs in a dose-dependent manner. Shotgun metagenomics analysis of samples (n = 32) from individuals of the lowest and highest exposure levels of PAHs further highlighted associations between the PAHs quantified and decrease in abundances of skin commensals and increase in oral bacteria. Functional analysis identified associations between levels of PAHs and abundance of microbial genes of metabolic and other pathways with potential importance in host-microbe interactions as well as degradation of aromatic compounds.ConclusionsThe results in this study demonstrated the changes in composition and functional capacities of the cutaneous microbiota associated with chronic exposure levels of PAHs. Findings from this study will aid the development of strategies to harness the microbiota in protecting the skin against pollutants.EdPNeYfwVemgFQnh9BH8shVideo

A Knowledge-Driven Network-Based Analytical Framework for the Identification of Rumen Metabolites.

Metabolites are the final production of biochemical reactions in the rumen micro-ecological system and are very sensitive to changes in rumen microbes. Nuclear magnetic resonance (NMR) spectroscopy could both identify and quantify the metabolic composition of the ruminal fluid, which reflects the interaction between rumen microbes and diet. The main challenge of untargeted metabolomics is the compound annotation. Based on non-linear and linear associations between microbial gene abundances and integrals derived from NMR spectra, combined with knowledge of enzymatic reaction from the KEGG database, this study developed a knowledge-driven network-based analytical framework for the inference of metabolites. There were 89 potential metabolites inferred from the integral co-occurrence network. The results are supported by dissimilarity network analysis. The coexistence of non-linear and linear associations between microbial gene abundances and spectral integrals was detected. The study successfully found the corresponding integrals for acetate, butyrate and propionate, which are the major volatile fatty acids (VFA) in the rumen. This novel framework could very efficiently infer metabolites to corresponding integrals from NMR spectra.

Sulfamethoxazole affects the microbial composition and antibiotic resistance gene abundance in soil and accumulates in lettuce.

Pot experiments were set up to simulate the soil contamination by three initial concentrations of sulfamethoxazole (SMX) (S1, 100mg/kg; S2, 200mg/kg; S3, 300mg/kg). The content of SMX in soil and its accumulation in lettuce were analysed. Additionally, the effects of SMX on soil microorganisms and antibiotic resistance genes were studied by Illumina high-throughput sequencing and droplet digital polymerase chain reaction (ddPCR). The results demonstrated that the SMX content in soil reduced by 97%, 86% and 75% in the S1, S2 and S3 treatment groups after 120days, respectively. The accumulated SMX in lettuce was positively correlated with the initial concentration of SMX in soil. SMX contamination significantly reduced the bacterial diversity and altered the composition of bacterial and fungal communities in soil. The dominant bacterial and fungal genera in the SMX-contaminated soil were obviously different from those in the control soil. The relative abundance of sul1 (sulfonamide resistance gene) remarkably increased in the SMX-contaminated soil, while that of other ARGs, such as sul2 and tetracycline and quinolone resistance genes, showed no significant change.

Microbial N-cycling gene abundance is affected by cover crop specie and development stage in an integrated cropping system.

Grasses of the Urochloa genus have been widely used in crop-livestock integration systems or as cover crops in no-till systems such as in rotation with maize. Some species of Urochloa have mechanisms to reduce nitrification. However, the responses of microbial functions in crop-rotation systems with grasses and its consequence on soil N dynamics are not well-understood. In this study, the soil nitrification potential and the abundance of ammonifying microorganisms, total bacteria and total archaea (16S rRNA gene), nitrogen-fixing bacteria (NFB, nifH), ammonia-oxidizing bacteria (AOB, amoA) and archaea (AOA, amoA) were assessed in soil cultivated with ruzigrass (Urochloa ruziziensis), palisade grass (Urochloa brizantha) and Guinea grass (Panicum maximum). The abundance of ammonifying microorganisms was not affected by ruzigrass. Ruzigrass increased the soil nitrification potential compared with palisade and Guinea grass. Ruzigrass increased the abundance of N-fixing microorganisms at the middle and late growth stages.The abundances of nitrifying microorganisms and N-fixers in soil were positively correlated with the soil N-NH4+ content. Thus, biological nitrogen fixation might be an important input of N in systems of rotational production of maize with forage grasses. The abundance of microorganisms related to ammonification, nitrification and nitrogen fixing and ammonia-oxidizing archea was related to the development stage of the forage grass.

Optimal influent COD/N ratio for obtaining low GHG emissions and high pollutant removal efficiency in constructed wetlands

Influent chemical oxygen demand (COD)/nitrogen (N) ratio plays a crucial role in the biogeochemical cycle of carbon and N in constructed wetlands (CWs). This study evaluated the greenhouse gas (GHG) emissions, pollutant removal efficiency and specific microbial gene abundances in subsurface flow CWs (SSFCWs) under various influent COD/N ratios. The GHG emissions and pollutant removal efficiency were markedly affected by influent COD/N ratios. The effluent concentrations of nitrate decreased with the increase of influent COD/N ratios, while the trend was completely reversed for COD. The lowest effluent total nitrogen concentration was observed with a COD/N ratio of 10. For GHG emissions, the CO2 fluxes increased with increasing influent COD/N ratios. However, the lowest CH4 (- 42.49 μg/m2/h) and N2O fluxes (31.77 μg/m2/h) were both observed under a COD/N ratio of 10. A significantly positive correlation between N2O fluxes and abundance of nirS and (nirS + nirK) (r2 = 0.64 and 0.61, p < 0.05, respectively) was observed. The highest ratio of nosZ/(nirS + nirK) observed at a COD/N ratio of 10 suggested the dominance of nosZ-harboring denitrifiers communities. The highest ratio of nosZ/(nirS + nirK) was also consistent with the lowest N2O flux observed at a COD/N ratio of 10. For the global warming potential (GWP), the lowest value (52.89 mg/m2/h) was observed at a COD/N ratio of 10. Overall, the influent COD/N ratio of 10 was determined to be optimal for simultaneously achieving relatively higher pollutant removal efficiency and lower GHG emissions.

Changes of microbial functional capacities in the rhizosphere contribute to aluminum tolerance by genotype-specific soybeans in acid soils

Changes in root exudates and rhizospheric microbial functional capacities involved in carbon (C) decomposition and nitrogen (N) transformation of aluminum (Al)-tolerant and Al-sensitive soybean genotypes were investigated under Al stress. Rhizosphere soils were collected from rhizobox systems with two soybean genotypes. A wide range of microbial functional capacities were determined by functional gene arrays. Microbial functional capacities of rhizospheres were distinct between Al-tolerant and Al-sensitive genotypes, which were related to exchangeable Al concentrations. Functional capacities associated with decomposition of chemically recalcitrant C were lower in Al-tolerant than Al-sensitive genotypes, which was negatively correlated with the secretion rate of succinic acid. Microbial functional capacities were higher for nitrification but lower for denitrification in the rhizosphere of Al-tolerant than Al-sensitive genotype, which coincided with higher succinic acid secretion and lower abundance of microbial oxygen stress genes. Soybean biomass increased logarithmically with nitrification capacities. We concluded that exchangeable Al concentrations, root exudation, and microbial C and N cycling capacities were intrinsically linked, which served as a key mechanism for legume genotypes toward enhancing tolerance to Al stress occurring in acid soils.

Impact of Irrigation Strategies on Tomato Root Distribution and Rhizosphere Processes in an Organic System.

Root exploitation of soil heterogeneity and microbially mediated rhizosphere nutrient transformations play critical roles in plant resource uptake. However, how these processes change under water-saving irrigation technologies remains unclear, especially for organic systems where crops rely on soil ecological processes for plant nutrition and productivity. We conducted a field experiment and examined how water-saving subsurface drip irrigation (SDI) and concentrated organic fertilizer application altered root traits and rhizosphere processes compared to traditional furrow irrigation (FI) in an organic tomato system. We measured root distribution and morphology, the activities of C-, N-, and P-cycling enzymes in the rhizosphere, the abundance of rhizosphere microbial N-cycling genes, and root mycorrhizal colonization rate under two irrigation strategies. Tomato plants produced shorter and finer root systems with higher densities of roots around the drip line, lower activities of soil C-degrading enzymes, and shifts in the abundance of microbial N-cycling genes and mycorrhizal colonization rates in the rhizosphere of SDI plants compared to FI. SDI led to 66.4% higher irrigation water productivity than FI, but it also led to excessive vegetative growth and 28.3% lower tomato yield than FI. Our results suggest that roots and root-microbe interactions have a high potential for coordinated adaptation to water and nutrient spatial patterns to facilitate resource uptake under SDI. However, mismatches between plant needs and resource availability remain, highlighting the importance of assessing temporal dynamics of root–soil–microbe interactions to maximize their resource-mining potential for innovative irrigation systems.

Abundance and diversity of microbial arsenic biotransformation genes in the sludge of full-scale anaerobic digesters from a municipal wastewater treatment plant

Arsenic (As) is a potential contaminant in sewage sludge that may affect waste treatment and limit the use of these waste materials as soil amendments. Anaerobic digestion (AD) is an important and effective process for the treatment of sewage sludge and the chemical speciation of As is particularly important in sludge AD. However, the biotransformation genes of As in sludge during AD has not been fully explored. In this study, the influent and effluent sludge of anaerobic digester in a wastewater treatment plant (WWTP) was collected to investigate the species transformations of As, the abundance and diversity of As biotransformation genes was explored by real-time PCR (qPCR) and metagenomic sequencing, separately. The results showed that arsenite [As(III)] and arsenate [As(V)] were predominant in the influent sludge, whereas the relative abundance of monomethylarsenic acid (MMA) increased by 25.7% after digestion. As biotransformation genes were highly abundant, and the As(III) S-adenosylmethionine methyltransferase (arsM) gene was the predominant which significantly increased after AD by qPCR analysis. Metagenomic analysis indicated that the diversity of the arsM-like sequences also increased significantly after AD. Most of the arsM-like sequences in all the influent and effluent sludge samples were related to Bacteroidetes and Alphaproteobacteria. Furthermore, co-occurrence network analysis indicated a strong correlation between the microbial communities and As. This study provides a direct and reliable reference on As biotransformation genes and microbial community in the AD of sludge.

Abstract MP44: Nitrite Generating Capacity Assessed Through the Oral Microbial Metagenome is Associated With Cardiometabolic Risk

Introduction: Nitric oxide (NO) is important for cardiometabolic health. The enterosalivary nitrate-nitrite-NO pathway generates NO following oral microbiota-mediated production of salivary nitrite. We investigated the association between the abundance of genes in this pathway and cardiometabolic biomarkers. Hypothesis: Microbial genes favoring increased oral nitrite generation are associated with better cardiometabolic profile. Methods: We enrolled 784 diabetes-free adults in the Oral Infections, Glucose Intolerance and Insulin Resistance Study (ORIGINS). Subgingival plaques were collected from 6-8 teeth/participant. 16S rRNA microbial genes (Illumina, MiSeq) were sequenced; PICRUSt2 estimated abundance of microbial genes in the nitrate-nitrite pathway associated with either nitrite generation or depletion. Gene abundance was summed within each group, and a ratio between nitrite generation to depletion (GDR) was calculated; higher levels suggest increased nitrite generating capacity. Systolic and diastolic blood pressure were measured and HbA1C, insulin, and glucose levels were determined in fasting blood. Z-scores were calculated for cardiometabolic biomarkers and averaged to form a cardiometabolic z-score (CMZ-score). Adjusted multivariable linear models were used to regress the CMZ-score and individual Z-scores on GDR. Results: Participants were 69% female and aged 19-58 years (mean=32±9). Mean CMZ-score was 0.00±0.7. Mean (range) GDR was 1.88 (0.22-7.84). Mean CMZ-scores (SE) across GDR quartiles were 0.17 (0.06), 0.01 (0.05), -0.04 (0.05), and -0.14 (0.05), p-value for trend=0.02. Linear regression coefficients summarizing associations between GDR and individual Z-scores (Table) show lower Z-score for systolic and diastolic blood pressure, HbA1C, and insulin levels in those with higher GDR. Conclusions: Increased capacity for nitrite production by oral bacteria, assessed through a metagenome estimation approach, is associated with lower levels of cardiometabolic risk.

Gut microbiota dysbiosis might be responsible to different toxicity caused by Di-(2-ethylhexyl) phthalate exposure in murine rodents

Di-(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer, which can enter the body through a variety of ways and exerted multiple harmful effects, including liver toxicity, reproductive toxicity and even glucose metabolism disorder. Many studies have suggested that changes of gut microbiota are closely related to the occurrence of various diseases, but the effects of DEHP exposure on gut microbiota are still unclear. It was found in this study that the damage to different tissues by DEHP on two strains each from two different species of male rodents before puberty was dose and time of exposure dependent, and also depending on the strain and species of rodent. Sprague-Dawley (SD) rats showed highest sensitivity to DEHP exposure, with most severe organ damage, highest Th1 inflammatory response and most significant body weight gain. Correspondingly, the gut microbiota of SD rats showed most significant changes after DEHP exposure. Only SD rats, but not Wistar rats, BALB/c and C57BL/6J mice showed an increase in Firmicutes/Bacteroidetes ratio and Proteobacteria abundance in the fecal samples, which are known to associate with obesity and diabetes. This is consistent with the increasing body weight gain which was only found in SD rats. In addition, the decrease in the level of butyrate, increase in the abundance of potential pathogens and microbial genes linked to colorectal cancer, Parkinson’s disease, and type 2 diabetes in the SD rats were associated with issue and functional damages and Th1 inflammatory response caused by DEHP exposure. We postulate that the differential effects of DEHP on gut microbiota may be an important cause of the differences in the toxicity on different strains and species of rodents to DEHP.

Nutrients release and greenhouse gas emission during decomposition of Myriophyllum aquaticum in a sediment-water system

Aquatic macrophytes play a significant role in nutrients removal in constructed wetlands, yet nutrients could be re-released due to plant debris decomposition. In this study, Myriophyllum aquaticum was used as a model plant debris and three debris biomass levels of 3 g, 9 g dry biomass, and 20 g fresh biomass (D3, D9, and F20, respectively) were used to simulate 120-d plant debris decomposition in a sediment-water system. The biomass first-order decomposition rate constants of D3, D9, and F20 treatments were 0.0058, 0.0117, and 0.0201 d−1, respectively with no significant difference of decomposition rate among three mass groups (p > 0.05). Plant debris decomposition decreased nitrate and total nitrogen concentrations but increased ammonium, organic nitrogen, and dissolved organic carbon (DOC) concentrations in overlying water. The parallel factor analysis confirms that three components of DOC in overlying water changed over decomposition time. Emission fluxes of methane and nitrous oxide in the plant debris treatments were several to thousands of times higher than the control group within the initial 0–45 d, which was mainly attributed to DOC released from the plant debris. Plant debris decomposition can affect the gas emission fluxes for relatively shorter time (30–60 d) than water quality (>120 d). The 16S rRNA, nirK, nirS and hazA gene abundance increased in the early stage for plant debris treatments, and then decreased to the end of 120-d incubation time while ammonia monooxygenase α-subunit A gene abundance of ammonia-oxidizing archaea and bacteria had no large variations during the entire decay time compared with no plant debris treatment. The results demonstrate that decomposition of M. aquaticum debris could affect greenhouse gas emission fluxes and microbial gene abundance in the sediment-water system besides overlying water quality.