Relative Abundance Of Dominant Phyla Research Articles

Effect of Forest Fires on the Alpha and Beta Diversity of Soil Bacteria in Taiga Forests: Proliferation of Rare Species as Successional Pioneers

Forest fires are among the most influential drivers of changes in forest soil bacterial diversity. Nevertheless, little is known regarding the effects of forest fires on maintaining the complex interactions that preserve forest ecosystem stability. Therefore, this study characterized alterations in soil bacterial community composition and diversity within taiga forests subjected to varying disturbance intensities. Particularly, this study examined the bacterial community within a Larix gmelinii fire-burnt site in Daxinganling, analyzing the changes in bacterial community structure and function across light, moderate, and heavy fire-burnt sites, as well as a control sample site, utilizing Illumina MiSeq technology. Through an assessment of bacterial community diversity and soil physicochemical properties (moisture content (MC), pH, microbial biomass carbon (MBC), organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AP)), we explored the influence of the soil microenvironment on the soil bacterial community structure at the burnt site under different disturbance intensities. Our findings demonstrated that (1) there was no significant change in the Chao index of soil bacteria in the burnt site under different disturbance intensities, whereas the Shannon index decreased significantly (p < 0.05) and the Simpson index increased significantly (p < 0.05) in the burnt site under light and moderate disturbance. (2) The relative abundance of dominant phyla, such as Proteobacteria, Proteobacteria, and Actinobacteriota, did not change significantly in the fire-burnt site under different disturbance intensities, whereas rare species, such as Acidipila, Occallatibacter, and Acidibacter, experienced a significant increase in relative abundance at the genus level. (3) The results of principal coordinates analysis (PCoA) and canonical correlation analysis (CCA) revealed significant differences in the Beta diversity of soil bacteria in the fire-burnt site under varying interference intensities. The Beta diversity of soil bacteria exhibited significant differences (p = 0.001), with MC, pH, TN, AN, and AK identified as significant influencing factors. (4) FAPROTAX functional prediction analyses were conducted to assess the changes in soil bacteria involved in Cellulolysis, Chemoheterotrophy, and Aerobic_Chemoheterotrophy in the fire-burnt site, with the relative abundance of bacteria involved in Chemoheterotrophy being significantly increased (p < 0.05) under different disturbance intensities. Collectively, our findings demonstrated that different disturbance intensities caused by fires significantly affected the Alpha diversity, Beta diversity, and functional abundance of soil bacterial communities in taiga forests, with MC, pH, TN, AN, and AK being identified as key influencing factors. Additionally, the presence of numerous rare species suggests their role as pioneer communities in the succession of soil bacterial communities.

Early Succession of Community Structures and Biotic Interactions of Gut Microbes in Eriocheir sinensis Megalopa after Desalination.

As an enduring Chinese freshwater aquaculture product, the Eriocheir sinensis has a high economic value and is characterized by a catadromous life style that undergoes seawater-freshwater migration. However, little is known about their gut microbial status as they move from saltwater to freshwater acclimatization. Here, we sampled and cultivated Eriocheir sinensis megalopa from three aquaculture desalination ponds and investigated their gut microbiota diversity, community structures and biotic interactions from megalopa stage to the first juvenile stage after desalination for 9 days. Our results revealed that during the transition from megalopa to the first juvenile in Eriocheir sinensis, a significant change in gut microbial composition was observed (for instance, changes in relative abundance of dominant phyla), which was, however, not influenced by different sampling sites. The species diversity (such as the richness) of the gut microbiota showed a hump-shaped pattern along the succession. However, the compositional differences of the gut microbes showed constantly increasing patterns during the succession after freshwater adaption for all three sampling sites. Further co-occurrence analysis also showed that the complexity of the ecological networks in gut microbes was significantly enhanced during the development, such as increasing numbers of network links, connectivity and modularity, and was confirmed by decreasing average path length and proportions of negative links. Taken together, the differences in community structures and biological interactions of gut microorganisms were more pronounced in Eriocheir sinensis megalopa during desalination than in diversity and species compositions. This implies that the gut microbes of Eriocheir sinensis megalopa would become more robust and adaptive during the developmental process.

Fine-scale spatiotemporal variations in bacterial community diversity in agricultural pond water

Microbial communities in surface waters are affected by environmental conditions and can influence changes in water quality. To explore the hypothesis that the microbiome in agricultural waters associates with spatiotemporal variations in overall water quality and, in turn, has implications for resource monitoring and management, we characterized the relationships between the microbiota and physicochemical properties in a model irrigation pond as a factor of sampling time (i.e., 9:00, 12:00, 15:00) and location within the pond (i.e., bank vs. interior sites and cross-sectional depths at 0, 1, and 2 m). The microbial communities, which were defined by 16S rRNA gene sequencing analysis, significantly varied based on all sampling factors (PERMANOVA P < 0.05 for each). While the relative abundances of dominant phyla (e.g., Proteobacteria and Bacteroidetes) were relatively stable throughout the pond, subtle yet significant increases in α-diversity were observed as the day progressed (ANOVA P < 0.001). Key water quality properties that also increased between the morning and afternoon (i.e., pH, dissolved oxygen, and temperature) positively associated with relative abundances of Cyanobacteria, though were inversely proportional to Verrucomicrobia. These properties, among additional parameters such as bioavailable nutrients (e.g., NH3, NO3, PO4), chlorophyll, phycocyanin, conductivity, and colored dissolved organic matter, exhibited significant relationships with relative abundances of various bacterial genera as well. Further investigation of the microbiota in underlying sediments revealed significant differences between the bank and interior sites of the pond (P < 0.05 for α- and β-diversity). Overall, our findings emphasize the importance of accounting for time of day and water sampling location and depth when surveying the microbiomes of irrigation ponds and other small freshwater sources.

Impact of altered groundwater depth on soil microbial diversity, network complexity and multifunctionality.

Understanding the effects of groundwater depth on soil microbiota and multiple soil functions is essential for ecological restoration and the implementation of groundwater conservation. The current impact of increased groundwater levels induced by drought on soil microbiota and multifunctionality remains ambiguous, which impedes our understanding of the sustainability of water-scarce ecosystems that heavily rely on groundwater resources. This study investigated the impacts of altered groundwater depths on soil microbiota and multifunctionality in a semi-arid region. Three groundwater depth levels were studied, with different soil quality and soil moisture at each level. The deep groundwater treatment had negative impacts on diversity, network complexity of microbiota, and the relationships among microbial phylum unites. Increasing groundwater depth also changed composition of soil microbiota, reducing the relative abundance of dominant phyla including Proteobacteria and Ascomycota. Increasing groundwater depth led to changes in microbial community characteristics, which are strongly related to alterations in soil multifunctionality. Overall, our results suggest that groundwater depth had a strongly effect on soil microbiota and functionality.

The Sensitivity of Belowground Ecosystem to Long‐Term Increased Nitrogen Deposition in a Temperate Grassland: Root Productivity, Microbial Biomass, and Biodiversity

AbstractStudies exploring ecosystem vulnerability to nitrogen (N) enrichment have mostly focused on aboveground components of ecosystems. However, the sensitivity of the belowground ecosystem to increasing N deposition remains unclear. We estimated responses of belowground net primary productivity (BNPP), soil microbial biomass N (MBN), N mineralization, nitrification, and 16S rRNA gene based bacterial diversity to elevated N inputs. The study was based on a long‐term N deposition experiment with monthly N applications at nine rates ranging from 0 to 50 g N m−2 yr−1 in a temperate grassland. BNPP, MBN, and microbial diversity showed non‐linearities across the N gradient. In both post‐hoc test and regression tree model, the significant decrease of BNPP relative to the control started at the 10 g N m−2 yr−1 rate (the 53% decrease), whereas in Bayesian regression model, the decrease started at the 5 g N m−2 yr−1 rate (the 39% decrease) in year 6. We therefore estimated a critical load range of 5–10 g N m−2 yr−1 for BNPP. Regression tree model, Bayesian regression, and post‐hoc test consistently suggested that the detrimental effects on MBN might occur above ∼10 g N m−2 yr−1 addition rate. Bacterial diversity and the relative abundance of dominant phyla declined when N addition rate exceeded 5 or 10 g N m−2 yr−1. The impacts of N deposition on the root‐microbe system strongly depended on the interannual fluctuation in precipitation. The responses of the sensitive belowground indicators are vital to help minimize the detrimental impacts of anthropogenic N inputs.

Characterization of Early and Late Damage in a Mouse Model of Pelvic Radiation Disease.

Pelvic radiation disease (PRD), a frequent side effect in patients with abdominal/pelvic cancers treated with radiotherapy, remains an unmet medical need. Currently available preclinical models have limited applications for the investigation of PRD pathogenesis and possible therapeutic strategies. In order to select the most effective irradiation protocol for PRD induction in mice, we evaluated the efficacy of three different locally and fractionated X-ray exposures. Using the selected protocol (10 Gy/day × 4 days), we assessed PRD through tissue (number and length of colon crypts) and molecular (expression of genes involved in oxidative stress, cell damage, inflammation, and stem cell markers) analyses at short (3 h or 3 days after X-ray) and long (38 days after X-rays) post-irradiation times. The results show that a primary damage response in term of apoptosis, inflammation, and surrogate markers of oxidative stress was found, thus determining a consequent impairment of cell crypts differentiation and proliferation as well as a local inflammation and a bacterial translocation to mesenteric lymph nodes after several weeks post-irradiation. Changes were also found in microbiota composition, particularly in the relative abundance of dominant phyla, related families, and in alpha diversity indices, as an indication of dysbiotic conditions induced by irradiation. Fecal markers of intestinal inflammation, measured during the experimental timeline, identified lactoferrin, along with elastase, as useful non-invasive tools to monitor disease progression. Thus, our preclinical model may be useful to develop new therapeutic strategies for PRD treatment.

The modified properties of sludge-based biochar with ferric sulfate and its effectiveness in promoting carbon release from particulate organic matter in rural household wastewater

The scarcity of carbon sources presents a significant challenge for the bio-treatment of rural domestic wastewater (RDW). This paper presented an innovative approach to address this issue by investigating the supplementary carbon source through in-situ degradation of particulate organic matter (POM) facilitated by ferric sulfate modified sludge-based biochar (SBC). To prepare SBC, five different contents of ferric sulfate (0%, 10%, 20%, 25%, and 33.3%) were added to sewage sludge. The results revealed that the pore and surface of SBC were enhanced, providing active sites and functional groups to accelerate the biodegradation of protein and polysaccharide. During the 8-day hydrolysis period, the concentration of soluble chemical oxidation demand (SCOD) increased and peaked (1087–1156 mg L−1) on the fourth day. The C/N ratio increased from 3.50 (control) to 5.39 (25% ferric sulfate). POM was degraded the five dominant phyla, which were Actinobacteriota, Firmicutes, Synergistota, Proteobacteria, and Bacteroidetes. Although the relative abundance of dominant phyla changed, the metabolic pathway remained unchanged. The leachate of SBC (<20% ferric sulfate) was beneficial for microbes, but an excessive amount of ferric sulfate (33.3% ferric sulfate) could have inhibition effects on bacteria. In conclusion, ferric sulfate modified SBC holds the potential for the carbon degradation of POM in RDW, and further improvements should be made in future studies.

The microbiome types of colorectal tissue are potentially associated with the prognosis of patients with colorectal cancer.

As the second leading cause of cancer worldwide, colorectal cancer (CRC) is associated with a poor prognosis. Although recent studies have explored prognostic markers in patients with CRC, whether tissue microbes carry prognostic information remains unknown. Here, by assessing the colorectal tissue microbes of 533 CRC patients, we found that Proteobacteria (43.5%), Firmicutes (25.3%), and Actinobacteria (23.0%) dominated the colorectal tissue microbiota, which was different from the gut microbiota. Moreover, two clear clusters were obtained by clustering based on the tissue microbes across all samples. By comparison, the relative abundances of Proteobacteria and Bacteroidetes in cluster 1 were significantly higher than those in cluster 2; while compared with cluster 1, Firmicutes and Actinobacteria were more abundant in cluster 2. In addition, the Firmicutes/Bacteroidetes ratios in cluster 1 were significantly lower than those in cluster 2. Further, compared with cluster 2, patients in cluster 1 had relatively poor survival (Log-rank test, p = 0.0067). By correlating tissue microbes with patient survival, we found that the relative abundance of dominant phyla, including Proteobacteria, Firmicutes, and Bacteroidetes, was significantly associated with survival in CRC patients. Besides, the co-occurrence network of tissue microbes at the phylum level of cluster 2 was more complicated than that of cluster 1. Lastly, we detected some pathogenic bacteria enriched in cluster 1 that promote the development of CRC, thus leading to poor survival. In contrast, cluster 2 showed significant increases in the abundance of some probiotics and genera that resist cancer development. Altogether, this study provides the first evidence that the tissue microbiome of CRC patients carries prognostic information and can help design approaches for clinically evaluating the survival of CRC patients.

Antibiotics affected the bacterial community structure and diversity in pore water and sediments with cultivated Phragmites australis in a typical Chinese shallow lake.

The migration of antibiotics and bacterial communities between sediments and pore water occurring in the lake, which is affected by aquatic vegetation. However, the differences in bacterial community structure and biodiversity between pore water and sediments with plants in lakes under antibiotic stress are still poorly understood. We collected pore water and sediments in both wild and cultivated Phragmites australis regions in the Zaozhadian (ZZD) Lake to explore the characteristics of the bacterial community. Our results showed that the diversity of bacterial community in sediment samples were significantly higher than those in pore water samples in both P. australis regions. Due to higher antibiotic levels in sediments from the cultivated P. australis region, the composition of bacterial communities showed a difference, which reduced the relative abundance of dominant phyla in pore water and increased that in sediments. The higher bacterial variations in pore water could be explained by sediment in the cultivated P. australis region than that in wild P. australis region, therefore plant cultivation might change the source-sink pattern between sediments and pore water. The dominant factors shaping the bacterial communities in the wild P. australis region pore water or sediment were NH4-N, NO3-N, and particle size, while cultivated P. australis region pore water or sediment were oxytetracycline, tetracycline, etc. The findings of this work indicates that the antibiotic pollution caused by planting activities has a greater impact on the bacterial community, which will provide a reference for the use and management of antibiotics in lake ecosystems.

Mycotoxin deoxynivalenol-induced intestinal flora disorders, dysfunction and organ damage in broilers and pigs

Deoxynivalenol (DON) is a common environmental contaminant that causes food refusal and growth retardation in animals. DON targets the intestine and is hazardous to animal, however, it is not clear whether its effect on animals is consistent. Chickens and pigs are the two main animals affected by DON exposure with different susceptibilities. In this study, we found that DON inhibited animal growth and caused damage to the intestine, liver and kidney. DON caused intestinal flora disorders in both chickens and pigs, such as changes of flora diversity and the relative abundance of dominant phyla. Functional analysis showed that changes in the intestinal flora induced by DON were mainly related to metabolic and digestive functions, indicated that the intestinal flora may be associated with the DON-induced intestinal dysfunction. Comparative analysis of differentially altered bacteria suggested that Prevotella may play an important role in maintaining intestinal health, and the presence of differentially altered bacteria in the two animals suggested that DON may have different toxicity modes in animals. In summary, we confirmed the multi-organ toxicity of DON in two major livestock and poultry animals, and speculated that the intestinal flora may be related to the toxic damage caused by DON through species comparison analysis.

Linking soil microbial community to the chemical composition of dissolved organic matter in a boreal forest during freeze–thaw cycles

Soil dissolved organic matter (DOM) is mainly derived from the microbial degradation of organic matter. Intense freeze–thaw cycles (FTCs) elicited by warming alter the production and consumption of DOM in boreal forest soils, but little is known about the interactions between soil microbial community and DOM chemical composition. In this study, a FTCs incubation experiment was conducted to investigate the association between DOM dynamics and microbial community. DOM fingerprints were characterized using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) technology, and bacterial and fungal community composition was analyzed using high-throughput sequencing and bioinformatics. Both two and six freeze–thaw cycles (2FTCs and 6FTCs) significantly increased soil dissolved organic carbon (DOC) and NH4+-N contents at 0–10 cm and 50–60 cm depths. FTCs significantly decreased the relative abundance of aromatic components in DOM, whereas increasing the relative abundance of polysaccharides and fatty acid methyl esters (FAMEs) in DOM. The degradation of lignin-derived aromatic compounds was accelerated and microbial-derived components accumulated. Also, bacterial community responded more sensitively to FTCs than fungal community. Significant changes in bacterial community network was observed during FTCs with increased linkages, shortened average path lengths, reduced modularity and relative abundance of dominant phyla, and decreased α diversity. However, FTCs only increased the average path length of soil fungal community. The higher connectivity indicated that FTCs enhanced the interactions between microbial community and DOM chemical components. FTCs led to a shift in bacterial keystone taxa from being present in specific DOM molecules to competing for common substrates. Overall, FTCs tended to activate DOM and increase availability, which could promote DOM turnover and increase soil C stabilization. These findings provide new insights into the molecular mechanisms of DOM dynamics in the boreal forest soils under increased FTCs.

Soil bacteria respond intensely to resource limitations regulated by edaphic properties during secondary succession on a semiarid abandoned farmland

Disproportionate inputs of carbon (C), nitrogen (N), and phosphorus (P) following plant succession typically induce microbial resource limitations. Such limitations are directly relevant to the fate of soil element cycles. However, it is not well understood how generalizable patterns of resource constraints act on soil microbial communities during the natural succession of abandoned farmlands, nor their driving forces. To this end, the potential activities of C-, N-, and P-acquiring enzymes, soil properties, plant characteristics, and soil microbial community composition and diversity were investigated along a 30-year successional chronosequence following agricultural abandonment on the Chinese Loess Plateau. Ecoenzymatic stoichiometry revealed a decrease in C limitation following succession, and soil microorganisms were primarily limited by N in the 10th year of succession but limited by P in the 20th and 30th years. Soil physicochemical properties cumulatively contributed 62.59% and 59.33% to the variations in microbial C and nutrient limitations, respectively. In particular, soil organic C content, C:N and C:P ratios, microbial biomass, and pH strongly affected microbial element limitations. Plant characteristics had minor effects on microbial resource constraints, accounting for 37.41% and 40.67% of the variance in microbial C and nutrient limitations, respectively. In comparison, plant diversity affected soil microbial element limitations more than plant family composition. Notably, the bacterial alpha and beta diversities, as well as the relative abundances of dominant phyla, such as Actinobacteria, Bacteroidetes, Proteobacteria, Acidobacteria, Gemmatimonadetes, and Planctomycetes, were significantly more associated with resource limitations than soil fungal community. Collectively, these findings suggest that the variable patterns of microbial element limitations were predominantly the result of changing soil properties across distinct successional stages, with soil bacteria responding more strongly than fungi to changes in microbial element limitations.

Effects of rhamnolipids on bacterial communities in a dioxin-contaminated soil and the gut of earthworms added to the soil

Biosurfactant rhamnolipid and “soil ecosystem engineers” earthworms are often used to remediate contaminated soils. However, the effect of rhamnolipid on earthworm intestinal flora and microbial community in soil with earthworms is not understood. In our study, microcosm experiments were carried out to reveal the rhamnolipid on microbial abundance, composition, metabolism and contaminant degradation capacity. The results showed that both rhamnolipids and earthworms could have positive effects on soil bacteria. Bacteria in soil with rhamnosis have higher abundance and metabolic activity than in earthworm-only soils, while the improvement of rhamnolipid in bacterial composition and their contaminant degradation capacity were lower than earthworms. Notably, these changes were further amplified when rhamnolipids and earthworms coexisted. Specifically, the (log(copies/g) value increased from 9.50 (CK) to 10.25 (E), 10.50 (R) and 11.00 (RE). Comparing the soil with only earthworms (E), the relative abundance of dominant phyla Proteobacteria increased from 41.66% to 51.67% in the soil with both rhamnolipid and earthworms (RE), and more pollutant-degrading bacteria were also enriched in soil RE. Therefore, the increase in bacterial abundance and the enrichment of degrading bacteria lead that the removal rate of soil dioxins was earthworms + rhamnolipid (RE, 77.28%) > earthworms (E, 59.83%) > rhamnolipid (R, 24.65%) > control treatment (4.71%). Moreover, the addition of rhamnolipid enhanced the abundance of bacterial functional genes involved in “Metabolism” and “Environmental information processing”. In addition, the composition and diversity of bacteria in earthworms’ gut was conspicuously affected by rhamnolipid too, and the relative abundance of Microbacterium and Shewanella increased significantly (p<0.05). In conclusion, this study reveals that rhamnolipid will prominently influence the abundance, composition and metabolism of the microbial community in earthworms’ gut and soil, further promoting the degradation rate of dioxins. This study provides theoretical support for optimizing the combined application of rhamnolipid and earthworms in bioremediation engineering and the assessment of the ecological impacts of rhamnolipids.

Assessing the performance and microbial structure of biofilms in membrane aerated biofilm reactor for high p-nitrophenol concentration treatment

P-nitrophenol (PNP) is a mono-nitrophenol compound that is highly toxic and difficult to degrade, causing great harm to the ecological environment and human health. In this study, a membrane aerated biofilm reactor (MABR) was used to degrade high PNP concentration without external carbon sources. This experiment mainly presented the process performance of MABR under high-load shock of PNP and variations in the community biodiversity and compositions of MABR biofilm. The experimental results showed that as the concentration of PNP in the influent gradually increased from 100 mg/L to 400 mg/L, the MABR exhibited a strong shockproof ability. The performance of the MABR peaked at an influent PNP concentration of 200 ± 50 mg/L, the removal efficiencies of PNP and chemical oxygen demand (COD) were 94.40% and 79.57%, respectively, and the removal loads were 3.644 g·m−2·d−1 and 4.975 g·m−2·d−1, respectively. The results of high-throughput sequencing revealed that MABR biofilms had high microbial richness and diversity, in which the microbial activity was not influenced by high-load shock. PNP, as a selective pressure, was used by microorganisms as the sole carbon source. The relative abundance of dominant phyla (Patescibacteria, Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidota), classes (Saccharimonadia, Clostridia, Actinobacteria, Bacilli, Gammaproteobacteria, Bacteroidia, and CPR2), and genera (TM7a, unclassified_o_Saccharimonadales, Proteiniclasticum, and norank_f_norank_o_Saccharimonadales) were different between the evaluated samples. Numerous candidate phyla radiation (CPR) bacteria were enriched in the MABR, indicating that CPR was the functional bacteria responsible for the degradation of high concentrations of PNP. The findings of this study demonstrated that the MABR system possesses great feasibility and potential for the advanced treatment of phenolic compounds.

The Role of Thermokarst Lake Expansion in Altering the Microbial Community and Methane Cycling in Beiluhe Basin on Tibetan Plateau.

Highlights The co-occurrence network structure of bacteria was more diverse and complex in sediment than in water, while archaea showed an opposite trend at environment under ice.Microbial diversity increased in MS and SH points, and microbial community composition and microbial network complexity were also different among four points.The diversity of functional gene mcrA and pmoA in water was positively correlated with dissolved methane concentration, and the water dissolved methane concentration was positively correlated with the diversity of functional gene mcrA but not with pmoA in sediment.The under-ice environment plays a vital role in the methane cycling of the thermokarst lake.One of the most significant environmental changes across the Tibetan Plateau (TP) is the rapid lake expansion. The expansion of thermokarst lakes affects the global biogeochemical cycles and local climate regulation by rising levels, expanding area, and increasing water volumes. Meanwhile, microbial activity contributes greatly to the biogeochemical cycle of carbon in the thermokarst lakes, including organic matter decomposition, soil formation, and mineralization. However, the impact of lake expansion on distribution patterns of microbial communities and methane cycling, especially those of water and sediment under ice, remain unknown. This hinders our ability to assess the true impact of lake expansion on ecosystem services and our ability to accurately investigate greenhouse gas emissions and consumption in thermokarst lakes. Here, we explored the patterns of microorganisms and methane cycling by investigating sediment and water samples at an oriented direction of expansion occurred from four points under ice of a mature-developed thermokarst lake on TP. In addition, the methane concentration of each water layer was examined. Microbial diversity and network complexity were different in our shallow points (MS, SH) and deep points (CE, SH). There are differences of microbial community composition among four points, resulting in the decreased relative abundances of dominant phyla, such as Firmicutes in sediment, Proteobacteria in water, Thermoplasmatota in sediment and water, and increased relative abundance of Actinobacteriota with MS and SH points. Microbial community composition involved in methane cycling also shifted, such as increases in USCγ, Methylomonas, and Methylobacter, with higher relative abundance consistent with low dissolved methane concentration in MS and SH points. There was a strong correlation between changes in microbiota characteristics and changes in water and sediment environmental factors. Together, these results show that lake expansion has an important impact on microbial diversity and methane cycling.

Changes in physicochemical property and microbial community of Pseudostellaria heterophylla soil at diffe-rent fallow ages

Pseudostellaria heterophylla is authentic traditional Chinese herbal medicine in Fujian Province. P. hete-rophylla suffers from serious consecutive monoculture problems. Fallow can alleviate such problems, but the mecha-nism is still unclear. In this study, high-throughput sequencing was performed to analyze the changes in soil microbial community structure and diversity in the P. heterophylla soil at different fallow ages as well as their relationships with soil physicochemical properties and phenolic acids. The results showed that fungal community diversity decreased but bacterial community diversity increased in fallow soils compared with the control soil of P. heterophy-lla. For bacterial communities, the relative abundance of Acidobacteria increased, while that of Proteobacteria and Actinobacteria decreased in fallow soils. For fungal communities, the relative abundance of dominant phyla had no significant difference between fallow and control soils. Soil acidity and organic matter content showed a trend of weakening and decreasing, respectively, with the increases of fallow years. In addition, with the increases of fallow years, the content of phenolic acids in soil, including benzoic acid and salicylic acid, showed significant decrease, while some other phenolic acids such as p-coumaric acid were accumulated obviously. Taken together, fallow could efficiently ameliorate the structure of soil microbial community and soil properties of P. heterophylla, and thus alleviate the effects of continuous cropping.

Diversity of Microbial Communities of Pinus sylvestris var. mongolica at Spatial Scale.

Soil microorganisms play an indispensable role in the forest ecosystem. It is necessary to study the soil microorganisms in Pinus sylvestris var. mongolica, which is one of the afforestation species widely planted in the northern sandy region of China. We collected soil samples of P. sylvestris at large spatial scales and analyzed bacterial and fungal community composition differences using high-throughput sequencing techniques. The results showed that: (1) the richness index of different sandy lands was significantly different. The α-diversity of bacteria was the highest in Mu Us Sandy Land, and the α-diversity of fungi was the highest in Horqin Sandy Land. (2) The dominant phyla of bacteria were Actinobacteria, Proteobacteria, Chloroflexi and Acidobacteria, while the dominant phyla of fungi were Ascomycota and Basidiomycota. The relative abundance of dominant phyla was different. (3) Temperature and precipitation were the main driving factors of bacterial and fungal community change at large spatial scale. In addition, bacteria were also affected by total nitrogen, soil organic carbon and pH content; fungal community was affected by pH. The microorganisms showed obvious differences in geographical distribution, which could provide ideas for promoting sustainable management of P. sylvestris stand.

Exposure to environmentally relevant oxytetracycline induced gut histopathological damages and microbiota alterations of Pelophylax nigromaculatus larvae

Antibiotics such as Oxytetracycline (OTC) is widely used around the world and it caused serious environmental issues in China, especially in Yangtze delta area. However, its effects on amphibian gut morphology and intestinal microbiota are still unclear. In this study, tadpoles of Pelophylax nigromaculatus was exposed to 0, 5, 90 and 450 μg/L OTC of environmentally relevant concentrations from Gosner (Gs) 26 to Gs 38. The results showed that severe histopathological injuries including cytoplasmic damage, cell arrangement disorganisation and structure deformation were observed in the gut of larvae in 90 and 450 μg/L OTC exposure groups. Moreover, Tunel assay also revealed higher apoptotic ratio in the intestine of tadpoles in 90 and 450 μg/L OTC treatment groups. Furthermore, the relative abundance of dominant phyla and genera of gut microbial community in OTC exposure groups was significantly different from that of control though the richness and species diversity did not show remarkable changes. We concluded that OTC may pose potential health risks to amphibian larvae through inducing gut histopathological injury and intestinal microbiota dysbiosis.

Effects of microplastic accumulation on floc characteristics and fouling behavior in a membrane bioreactor

Issues associated with accumulating microplastic (MP) in sewage sludge during wastewater treatment in a membrane bioreactor (MBR) system have not been studied in detail. Here, we investigated the microplastic’s effects on floc characteristics, microbial community compositions, and fouling behavior inside sequencing-batch MBRs. MBRs were operated with 0, 7, 15, and 75 MPs/L of feed for 124-days. Results indicated that MP presence decreased sludge floc size, floc hydrophobicity, and extracellular polymeric substance (EPS) molecular size, and increased EPS concentration and the floc’s negative zeta potential. These results were attributed to the facilitation of divalent cation (Ca2+ and Mg2+) uptake by MPs that weakened ion-bridging interactions within the sludge flocs. MPs accumulation slightly affected microbial structure and diversity. Relative abundances of dominant phyla, Actinobacteria, also decreased substantially. MPs also acted like a scouring material on membrane surfaces, inducing transformation of matured biofilm structures where protein content was substantially lower than nucleic acid content, in contrast to the control. Overall, MPs’ negative effects on sludge flocs were counteracted by their scouring effect; consequently, SB-MBRs operated up to 4 months did not suffer from severe cake fouling, compared to control.

Microbial mechanism of biochar addition on nitrogen leaching and retention in tea soils from different plantation ages

The effect of biochar additions on N leaching and retention in tea soils and its microbial mechanism are still unclear. In this study, effects of biochar additions at rates of 0, 3% and 6% on N leaching, N retention and microbial responses in two tea soils with 20- and 60-year plantation ages were investigated under application with 15N-labeled urea. The results showed that cumulative mass of leached NH4+-N, NO3−-N and TN was reduced by 20.9%–91.9%, 35.1%–66.9% and 40.0%–72.8% under biochar additions, respectively. The retention of TN in soil was increased by 1.2%–5.8% under biochar amendment. Fertilizer-N in the leachate was reduced by 28.8%–62.1%, while fertilizer-N retention in the soils was enhanced by 3.2%–23.9% with biochar application. Biochar addition of 6% showed the highest mitigation of N leaching and enhancement of TN retention across the two soils. Biochar additions increased soil microbial biomass and enzyme activities and changed the bacterial community composition, indicating that biochar addition increased the microbial N requirement, stimulated soil N cycling, including nitrification and denitrification processes, and enhanced microbial N immobilization in the tea soils. Those microbial responses to biochar addition were higher in 60-year-old soil relative to 20-year-old soil, leading to a higher enhancement of N retention and mitigation of N leaching. Soil pH was the prime factor that influenced soil microbes, and it strongly correlated with microbial biomass, enzyme activity, the relative abundance of dominant phyla and α-diversity indices. Therefore, the enhancement of microbial biomass, activity and shifts of bacterial community composition related to N cycling in response to biochar additions that increased the soil pH could be an important mechanism to better understand the biochar-induced N leaching mitigation and N retention enhancement in tea soils under different plantation ages.