Dominant Bacteria Research Articles

Characteristic flavor compounds and bacterial community of different gray sufu, a traditional Chinese fermented soybean curd

ABSTRACT Gray sufu is a traditional Chinese fermented soybean curd, and its flavor is significantly influenced by bacterial community. In this study, volatile flavor compounds (VFCs) were examined by headspace solid‐phase microextraction (HS-SPME) in conjunction with gas chromatography and mass spectrometry (GC‐MS). Additionally, bacterial community was analyzed using high-throughput sequencing. The results showed that, a total of 156 VFCs were tentatively identified, in which 8 esters, 6 S/N-containing compounds, 3 alcohols, 3 aldehydes, 1 ketone and 3 other compounds were recognized as the main characteristic VFCs. The abundant S/N-containing compounds are the most important flavor characteristics of gray sufu. A total of 4 phyla and 12 genera were revealed as dominant bacteria. Firmicutes and Proteobacteria were the most abundant phylum, whereas Bacillus, Tetragenococcus and Lactococcus were the prevailing genera. According to the KEGG pathway annotation, amino acid metabolism (26.98%) was the highest metabolic pathway. Among them, aromatic amino acids metabolism accounted for the highest proportion, up to 34.94%. Correlation analysis showed that Lactobacillus, Tetragenococcus, Bacillus, Pseudomonas and Halanaerobium were the top five positive flavor-producing bacteria. The results will be helpful for understanding the fermentation mechanism of gray sufu and improving flavor quality by developing microbial regulation strategies.

The improvement of storage quality of Harbin red sausage by coating with oregano essential oil loaded zein-pectin-chitosan nanoparticles

The effect of coating of oregano essential oil loaded zein pectin chitosan nanoparticles (Zein-PC-CS-OEO) to improve the quality of Harbin red sausage during storage was investigated. Firstly, Zein-PC-CS-OEO nanoparticles were prepared and characterized. Subsequently, Zein-PC-CS-OEO nanoparticles (EN-OEO) added sodium alginate solutions were successfully coated on the Harbin red sausage at different concentrations. All the sausages were stored at 20 °C and 65% relative humidity for 12 d, and subsequently sampled at 0, 3, 6, 9, and 12 d. The physicochemical properties, total number of aerobic bacteria, bacterial community structure and flavor characteristics for the Harbin red sausage were measured. Both lipid oxidation and the growth of dominant spoilage bacteria in Harbin red sausage are inhibited by EN-OEO coating, while the total aerobic bacteria count is reduced. These results indicate that the storage quality of Harbin red sausage is improved by EN-OEO coating. It is worth noting that the shelf life of the Harbin red sausage with 3% EN-OEO coating is extended to 9 d and the flavor characteristics of Harbin red sausage can be better preserved compared with the Control sample and the unencapsulated samples. This study provides a new thought for the preservation of Harbin red sausage as well as other low-temperature meat products.

Anammox process in anaerobic baffled biofilm reactors with columnar packings: Characteristics of flow field and microbial community

The enrichment of anammox bacteria is a key issue in the application of anammox processes. A new type of reactor － anaerobic baffle biofilm reactor (ABBR) developed from anaerobic baffle reactor (ABR) was filled with columnar packings and established for effective enrichment of anammox bacteria. The flow field analysis showed that, compared with ABR, ABBR narrowed the dead zone so as to improve the substrate transferring performances. Two ABBRs with different types of columnar packings (Packings 1 and Packings 2) were constructed to culture anammox biofilms. Packings 1 consisted of the single-form honeycomb carriers while Packings 2 was modular composite packings consisting of non-woven fabric and honeycomb carriers. The effects of different types of columnar packings on microbial community and nitrogen removal were studied. The ABBR filled with Packings 2 had a higher retention rate of biomass than the ABBR filled with Packings 1, making the anammox start-up period be shortened by 21.28%. The enrichment of anammox bacteria were achieved and the dominant anammox bacteria were Candidatus Brocadia in both R1 and R2. However, there were four genera of anammox bacteria in R2 and one genus of anammox bacteria in R1, and the cell density of anammox bacteria in R2 was 95% higher than that in R1. R2 has the advantage of maintaining excellent and stable nitrogen removal performance at high nitrogen loading rate. The results revealed that the packings composed of two types of carriers may have a better enrichment effect on anammox bacteria. This study is of great significance for the rapid enrichment of anammox bacteria and the technical promotion of anammox process.

Abstract 758: Comparative Microbiome Analysis of Paired Mucosal and Fecal Samples in Korean Colorectal Cancer Patients

Abstract Background Beyond the known risk factors such as age over 50, unhealthy diet, ethnicity, and smoking, emerging evidence suggests that gut microbial dysbiosis plays a crucial role in the early stages of colorectal cancer (CRC) by contributing to chronic inflammation and various intestinal dysfunctions. Even though various bacterial species have been studied, the gut microbiome profile as a representative biomarker in CRC patients remains largely unreported. This study presents a comparative analysis of the microbiome profiles of fecal and mucosal samples from CRC patients, followed by metagenomic profiling investigation to validate dominant bacteria in each sample type of CRC patients. Methods The study involved 12 patients receiving CRC resection at Myongji Hospital in South Korea, recruited from May 2020 to June 2021. Fecal samples were collected pre-surgery, and mucosal samples during surgery. Paired-end sequencing was performed using Illumina MiSeq (Illumina, San Diego, USA) platform. 16s rRNA gene-based microbiome profiling was analyzed using QIIME2 (V.2020.11), a plugin-based platform for microbiome analysis. Sequencing reads were filtered, denoised, and clustered into amplicon sequence variants (ASVs) using DADA2 included in QIIME2. Taxonomic classification was assigned in the QIIME2 pipeline using a pre-trained classifier based on the Silva 138.1 reference sequence. Linear discriminant analysis (LDA) effect size (LEfSe) analysis was performed with LDA score ≥3.0 and p-value of 0.05. Results The study subjects included 12 Korean patients, with an average age of 71 ± 10 years. The gender distribution included 3 men and 9 women whose body mass index was 24.6 ± 2.4 (mean ± SD). There was significant difference observed in UniFrac beta-diversity between the two groups (p=0.001). The relative taxonomic patterns of the microbiota between CRC stool and tissue showed that Bacteroides and Fusobacterium were more dominant in tissue than stool at both phylum and genus levels. Further taxonomic differences between the samples revealed that Firmicutes, Bacilli, and Lactobacillacease were over-represented in CRC patient stool, while Pseudomonadales (p<0.001) and Pseudomonas (p<0.001) were identified in the mucosal tissue. Conclusion Our findings revealed that notable distinction was observed in the beta-diversity, indicating a unique microbial composition in tissue. Specifically, higher prevalence of Bacteroides and Fusobacterium at the genus level were identified in tissue. Additionally, our analysis highlighted Pseudomonadales and Pseudomonas emerged in CRC mucosal tissues. Furthermore, by comparing with a healthy control group, we aim to further elucidate potential markers unique to CRC patients. Citation Format: Sanghun Lee. Comparative Microbiome Analysis of Paired Mucosal and Fecal Samples in Korean Colorectal Cancer Patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 758.

Analysis of intestinal bacterial diversity and its gene function prediction in black-capped capuchin (Sapajus apella)

ABSTRACT In this study, we used high-throughput sequencing technology to analyze the diversity and predict gene function of intestinal bacteria from captive black-capped capuchin in two wildlife parks. The results showed that the composition of intestinal gut bacterial diversity was significantly higher in black-capped capuchins monkeys from ES than HT. Moreover, high similarity of intestinal bacteria of black-capped capuchins at the same site was found by sample stratum clustering. Black-capped capuchins intestinal bacteria can be clustered into 2296 ASVs, belonging to 16 phyla, 99 families and 210 genera, respectively. The dominant phyla were Bacteroidota and Firmicutes in the intestinal bacteria of black-capped capuchins, but there were differences in the dominant bacterial families and dominant bacterial genera between ES and HT, and the bacterial families with significant differences had correspondence with bacterial genera. The results provide a basis for the study of intestinal bacteria in black-capped capuchins and the isolation and purification of dominant bacteria. The results of this study fill the gap in the study of intestinal bacterial diversity and its gene functions in black-capped capuchins, and provide a reference for the isolation of dominant bacteria in black-capped capuchins’ intestinal microbes and the discovery and study of novel functional genes.

Mitigating Tetracycline antibiotic contamination in chicken manure using ex situ fermentation system

Excessive use of tetracycline antibiotics in poultry farming results in significant concentrations of these drugs and tetracycline resistance genes (TRGs) in chicken manure, impacting both environmental and human health. Our research represents the first investigation into the removal dynamics of chlortetracycline (CTC) and TRGs in different layers of an ex situ fermentation system (EFS) for chicken waste treatment. By pinpointing and analyzing dominant TRGs-harboring bacteria and their interactions with environmental variables, we've closed an existing knowledge gap. Findings revealed that CTC's degradation half-lives spanned 3.3–5.8 days across different EFS layers, and TRG removal efficiency ranged between 86.82% and 99.52%. Network analysis highlighted Proteobacteria and Actinobacteria's essential roles in TRGs elimination, whereas Chloroflexi broadened the potential TRG hosts in the lower layer. Physical and chemical conditions within the EFS influenced microbial community diversity, subsequently impacting TRGs and integrons. Importantly, our study reports that the middle EFS layer exhibited superior performance in eliminating CTC and key TRGs (tetW, tetG, and tetX) as well as intI2. Our work transcends immediate health and environmental remediation by offering insights that encourage sustainable agriculture practices.

Enhanced hydrolysis and acidification of corn straw via liquid fraction of digestate: Environmental adaptability and microbial mechanisms

Anaerobic digestion (AD) of abandoned straws is an eco-friendly approach to realize its recycling. However, the low hydrolysis rate of lignocellulose poses a hindrance to achieving efficient AD. In this study, the enhanced hydrolysis and acidification of corn straw (CS) utilizing the liquid fraction of digestate (LFD) was investigated across varying solid-to-liquid inoculum ratio (SIR), pH levels, and temperature conditions. The succession patterns of the microbial community, driven by different parameters, were simultaneously identified. The findings revealed that the optimal yield of volatile fatty acids (VFAs) was observed under conditions with an SIR of 4, pH of 10, and a temperature of 45℃, predominantly dominated by acetic acid. And both pH and temperature were not conducive to VFAs accumulation in extreme environments. Comparatively, changes in pH had a greater impact on the acid production of the LFD-enhanced system and was also the primary environmental factor leading to differentiation in microbial community structure. Although Firmicutes was an absolutely dominant bacterium at the phylum level, the abundances of Caproiciproducens and Clostridum_sensu_stricto_1 at the genus level, mainly transforming complex organic substances into simpler metabolic byproducts, were greatly sensitive to the variations in SIR, pH, and temperature. This study could have practical implications for guiding improvements in large-scale AD systems with lignocellulosic straws.

Comparison of Intestinal Bacteria of Procambarus clarkii Farmed in Various Rice Paddy Regions.

The aim of this study was to assess the regional differences of Procambarus clarkii through analyzing gut microbiota in specimens from different areas in China. The P. clarkii were collected from ten integrated rice-crayfish farming systems locating across ten major producing areas as follows: Feixi (FX), Suqian (SQ), Yangzhou (YZ), Xuyi (XY), Qianjiang (QJ), Jianli (JL), Honghu (HH), Yueyang (YY), Changsha (CS), and Nanxian (NX). The composition of gut microbiota was assessed by analyzing 16S rRNA sequences. The PCoA results indicated significant differences in microbial community composition among the ten areas (R = 0.999, p = 0.001). The intestinal microbial diversity in P. clarkii cultured in rice fields from YY and CS exceeded that of other regions, with NX displaying the least diversity. At the phylum level, Proteobacteria were most abundant in HH, while Firmicutes showed increased relative abundances in FX and SQ, contrasted by lower relative abundances of Bacteroidetes in these areas. At the genus level, Ralstonia, Amedibacillus, Bacteroides, Anaerorhabdus, and Dysgonomonas were the dominant bacteria. The bacterial co-occurrence networks analysis revealed that the community structures in locations FX, SQ, XY, HH, and NX were comparatively simplistic, whereas those in the YZ, QJ, JL, YY, and CS regions displayed as more complex. In summary, the diversity and relative abundance of intestinal bacteria exhibits regional variability. These findings can offer theoretical data for evaluating the quality of P. clarkii aquaculture.

Isolation, identification and characterisation of Pseudomonas koreensis CM-01 isolated from diseased Malaysian mahseer (Tor tambroides)

Pseudomonas species are one of the most threatening fish pathogens which reside a wide range of environments. In this study, the dominant bacteria were isolated from diseased Malaysian mahseer (Tor tambroides) and tentatively named CM-01. It was identified as Pseudomonas koreensis based on its biochemical, morphological, genetic and physiological information. Its pathogenicity was found to be correlated with twelve virulence genes identified including iron uptake, protease, acylhomoserine lactone synthase gacS/gacA component regulation system, type IV secretion system, hydrogen cyanide production, exolysin, alginate biosynthesis, flagella and pili. The median lethal dose (LD50) for the CM-01 isolate on Malaysian mahseer was documented at 5.01 × 107 CFU/mL. The experimental infection revealed that CM-01 led to significant histological lesions in the fish, ultimately resulting in death. These lesions comprise necrosis, tissue thickening and aggregation. Drug sensitivity tests had shown its susceptibility to beta-lactam combination agents and further suggest its drug of choice. Its growing features had shown its growth at optimal temperature and pH. To the best of our knowledge, this is the first report of P. koreensis linked to diseased T. tambroides. Statement of relevanceIn this research, a novel strain of Pseudomonas koreensis, CM-01 was isolated from diseased T. tambroides for the first time. The antimicrobial susceptibility, pathogenicity, virulence genes and growth characteristics of CM-01 were studied. These findings established a scientific foundation for the recognition of P. koreensis and the management of fish infections caused by this pathogen.

Construction of integrated oxygen-rich carbon-based metal-free cathode to simultaneous boost wastewater treatment performance and energy recovery in bio-electro-Fenton system

Fenton coupled microbial fuel cells (MFCs) used for antibiotic pollution purification are limited by energy recovery and metal leakage of electrode. Here, we constructed a two-compartment bio-electro-Fenton (MFC-Fenton) with biological anode and Fenton cathode, which using carbon nanotube based on carbon brushes (OCNT-80/CB) with active centers rich in oxygen-containing functional groups as metal-free cathode. The results show that C = O locked environmental oxygen in the cathode can in-situ use the electrons produced by the anode through two-electron oxygen reduction reaction (2e− ORR) synthesize H2O2. •OH is further generated under activation of H2O2, achieving effective degradation of tetracycline (TC) in the cathode chamber. This study breaks through the limitations of poor pH adaptability and environmental secondary pollution caused by metal dissolution. Moreover, with the advantageous features of oxygen-containing functional groups active centers, good conductivity, and cyclic stability, the OCNT-80/CB achieves a maximum power density increased by 79.4 % as compared to that of the CB control. More notably, Microbial analysis further indicated that OCNT-80/CB electrode could simultaneously enhance Proteobacteria and Firmicutes abundance in bioanode. Dominant bacteria can self-metabolize environmental wastewater generate and recycle green energy. This study proved that careful structural design of cathode could promote the electrode performance. MFC-Fenton can be a competitive technology to enhance wastewater treatment and energy recovery simultaneously.

DL-Methionyl-DL-Methionine/DL-Methionine Supplementation Alleviated the Adverse Effects of Dietary Low Fishmeal Levels on Growth and Intestinal Health of Micropterus salmoides.

DL-methionyl-DL-methionine (AQUAVI® Met-Met) (Met-Met) (0.10%, 0.20%, 0.30%, and 0.40%) or DL-methionine (DL-Met) (0.10%, 0.20%, 0.30%, and 0.40%) were added to a low-fishmeal diet in an attempt to reduce fishmeal in the diet of Micropterus salmoides (M. salmoides). The fish were randomly allocated into ten experimental groups (n = 100), each with 4 replicates of 25 fish (16.39 ± 0.01 g) each. Compared to 25% FM, 0.40% of DL-Met and 0.10% of Met-Met promoted growth, and 0.10% of Met-Met decreased FCR. Compared to 25% FM, the supplementation of Met-Met or DL-Met improved the intestinal antioxidant capacity by upregulating the NF-E2-related factor 2-mediated antioxidant factors and enzyme activities and nuclear factor kappa-B-mediated anti-inflammatory factors while downregulating the pro-inflammatory factors, thereby exerting anti-inflammatory effects. Moreover, 0.10% of the Met-Met diet affected the Firmicutes-to-Bacteroidota ratio, increased the levels of Proteobacteria, changed the composition of intestinal flora (Roseburia, Lachnospiraceae_NK4A136_group, and unclassified_Oscillospiraceae), and enhanced intestinal dominant bacteria (Caldicoprobacter, Pseudogracilibacillus, and Parasutterella), leading to improved gut health. In summary, the supplementation of DL-Met or Met-Met alleviated the adverse effect of fishmeal reduction (from 40 to 25%) on the growth performance and intestinal health of M. salmoides.

The fate of antibiotic resistance genes and their correlation with microbial communities and wastewater quality/parameters in a wastewater treatment plant under different seasons

Wastewater treatment plants (WWTPs) are the hardest hit areas of antibiotic resistance genes (ARGs) pollution. As an emerging contaminant, ARGs seriously threaten ecological, human, and livestock safety. It is research interest to understand the potential relationship between ARGs, wastewater quality/parameters, and microbial communities. Herein, we compared that the variation of ARGs, wastewater quality/parameters, and microbial communities along the whole treatment processes in the WWTP in summer and winter. Results showed that ARGs abundance in summer is higher than that in winter, and the removal efficiency of ARGs varies with season. In summer, ARGs abundance had a significant correlation with phosphorus concentration, but in winter changed to the content of heavy metals (HM). Meanwhile, the dominant bacteria genera and their abundance were distinct in different seasons. The network analysis illustrated that ARGs are correlated with bacterial genera. Throughout this study, we found that wastewater quality/parameters and microbial community play a key role in the formation of ARGs, and the relationship among them is driven by seasonal variation. This work will help to provide a direction for optimizing wastewater treatment processes and controlling the spread of ARGs from the WWTPs to aquatic environment.

Evaluation of polyhydroxyalkanoate recovery from food waste by sequencing batch biofilm reactor with high mixed microbial biomass

In this study, the enrichment sequencing batch biofilm reactor (SBBR) and conventional enrichment reactor (SBR) were established, and a new strategy was developed to achieve higher biomass yield and polyhydroxyalkanoate (PHA) production from food waste than those achieved through the conventional method. After the 10th day of an expanded cultivation period, the respective active biomass concentrations in SBR and SBBR were 5.16 and 13.92 g/L, indicating a significant improvement in the biomass yield of mixed microbial culture in the SBBR. The PHA accumulation test revealed that maximum PHA concentration in SBR and SBBR reached 6.60 and 12.70 g/L, respectively, after 80 days of enrichment, indicating that compared to SBR, the SBBR could more effectively improve the PHA accumulation capacity. Meganema, Thauera, and Paracoccus were the dominant PHA-accumulating bacteria in the SBR and SBBR. Additionally, the volumetric productivity of the SBBR was 3.22 g COD/L/d, twice that of the SBR. This study provides new strategies and insights for improving PHA production and reducing the costs of PHA production and reactor investment.

The accumulation of active ingredients of Polygonatum cyrtonema Hua is associated with soil characteristics and bacterial community.

With the increasing demand for health products derived from Polygonati rhizoma (PR), people begin to artificially plant Polygonatum cyrtonema Hua (P. cyrtonema) in the middle and lower reaches of the Yangtze River. To promote P. cyrtonema cultivation and increase farmers' income, efforts are needed to understand the ways to obtain high-quality PR under artificial cultivation conditions. Rhizomes of artificial planting P. cyrtonema and rhizosphere soils were collected across five regions in Zhejiang Province, China. Subsequently, the contents of the main active ingredients of P. cyrtonema and soil properties were analyzed, and both rhizosphere and endophytic bacteria of P. cyrtonema were detected by 16S rDNA sequencing. The relationship between the active ingredients and soil properties, and the dominant bacteria were investigated by correlation analysis. The content of active ingredients of P. cyrtonema from the five regions varied significantly, especially polysaccharides and saponins. High-throughput sequencing demonstrated that Proteobacteria was the dominant bacterial phylum in all samples, and Burkholderia-Caballeronia-Paraburkholderia was the main endophytic bacterial genus in rhizome. In addition, the bacterial diversity and richness of rhizosphere soil samples were higher than those of rhizome samples. Soil physicochemical properties and enzyme activities were significantly different across regions, leading to notable variations in the community structures of rhizosphere and endophytic bacteria. Redundancy analysis (RDA) displayed that pH and urease (UE) were the major factors altering shifting rhizosphere bacteria community structure. Moreover, the composition and diversity of rhizome endophytic bacteria were principally affected by both soil physicochemical properties and soil enzyme activities. Soil properties and bacteria from rhizosphere soil and rhizome had a considerable impact on certain active ingredients in P. cyrtonema under artificial cultivation conditions after Pearson correlation analysis. Polysaccharides were significantly correlated with nutrient-rich soil and endophytic bacteria, such as Burkholderia-Caballeronia-Paraburkholderia, Pseudomonas, Ralstonia, and Bacillus. However, flavonoids were associated with nutrient-poor soil. Saponins were positively correlated with OM and available phosphorous (AP) and were significantly negatively affected by rhizosphere bacterial communities. The study demonstrated that bacterial microorganisms were involved in the accumulation of active ingredients of P. cyrtonema together with soil physicochemical properties and enzyme activities, which provided a theoretical basis for the scientific and effective artificial cultivation of high-quality P. cyrtonema.

Revealing extracellular protein profile and excavating spoilage-related proteases of Aeromonas salmonicida based on multi-omics investigation

Aeromonas is a ubiquitous aquatic bacteria, and it is a significant factor contributing to meat spoilage during processing and consumption. The abilities of Aeromonas salmonicida 29 and 57, which exhibit spoilage heterogeneity, to secrete protease, lipase, hemolysin, gelatinase, amylase, and lecithinase were confirmed by plate method. A total of 3948 proteins were identified by ITRAQ in extracellular secretions of A. salmonicida, and 16 proteases were found to be potentially related to spoilage ability. The complete genome sequence of A. salmonicida 57 consists of one circular chromosome and three plasmids, while A. salmonicida 29 consists of one circular chromosome, without a plasmid. Transcriptomic analysis revealed a significant number of DEGs were up-regulated in A. salmonicida 29, which were mainly enriched in metabolic pathways (e.g., amino acid metabolism, carbohydrate metabolism), indicating that A. salmonicida 29 had better potential to decompose and utilize nutrients in meat. Six protease genes (2 pepB, hap, pepA, ftsI, and pepD) were excavated by combined ITRAQ with transcriptome analysis, which potentially contribute to bacterial spoilage ability and exhibit universality among other dominant spoilage bacteria. This investigation provides new insights and evidence for elucidating metabolic and spoilage phenotypic differences and provides candidate genes and strategies for future prevention and control technology development.

Impact of stepwisely reducing settling time on the formation and performance of aerobic granular sludge

The impact of gradually reducing the settling time strategy on the formation, performance, and microbial succession of aerobic granular sludge (AGS) was investigated in a sequencing batch reactor (SBR). The results showed that the short settling time accelerated the granulation of AGS and the granulation was completed within 35 d. When the settling time was 10 min, the granular sludge had good settling performance and significant biological activity, and the average particle size and integrity coefficient increased to 1.017 mm and 93.3 %. The shortening of settling time stimulated bacteria to secrete more extracellular polymeric substances (EPS). Three-dimensional fluorescence spectrum analysis showed that aromatic proteins had high fluorescence intensity. According to the analysis of high-throughput sequencing, Rhodanobacter and Klebsiella were the dominant bacteria, and carbohydrate metabolism and amino acid metabolism were significantly enhanced, which may play an important role in maintaining the stability of AGS.

The impact of microbial community structure changes on the migration and release of typical heavy metal (loid)s during the revegetation process of mercury-thallium mining waste slag

The effect of changes in microbial community structure on the migration and release of toxic heavy metal (loid)s is often ignored in ecological restoration. Here, we investigated a multi-metal (mercury and thallium, Tl) mine waste slag. With particular focus on its strong acidity, poor nutrition, and high toxicity pollution characteristics, we added fish manure and carbonate to the slag as environmental-friendly amendments. On this basis, ryegrass, which is suitable for the remediation of metal waste dumps, was then planted for ecological restoration. We finally explored the influence of changes in microbial community structure on the release of Tl and As in the waste slag during vegetation reconstruction. The results show that the combination of fish manure and carbonate temporarily halted the release of Tl, but subsequently promoted the release of Tl and arsenic (As), which was closely related to changes in the microbial community structure in the waste slag after fish manure and carbonate addition. The main reason for these patterns was that in the early stage of the experiment, Bacillaceae inhibited the release of Tl by secreting extracellular polymeric substances; with increasing time, Actinobacteriota became the dominant bacterium, which promoted the migration and release of Tl by mycelial disintegration of minerals. In addition, the exogenously added organic matter acted as an electron transport medium for reducing microorganisms and thus helped to reduce nitrate or As (Ⅴ) in the substrate, which reduced the redox potential of the waste slag and promoted As release. At the same time, the phylum Firmicutes, including specific dissimilatory As-reducing bacteria that are capable of converting As into a more soluble form, further promoted the release of As. Our findings provide a theoretical basis for guiding the ecological restoration of relevant heavy-metal (loid) mine waste dumps.

Effect of bioaugmentation on gas production and microbial community during anaerobic digestion in a low-temperature fixed-bed reactor.

Low temperature is one of the limiting factors for anaerobic digestion in cold regions. To improve the efficiency of anaerobic digestion for methane production in stationary reactors under low-temperature conditions, and to improve the structure of the microbial community for anaerobic digestion at low temperatures. We investigated the effects of different concentrations of exogenous Methanomicrobium (10, 20, 30%) and different volumes of carbon fiber carriers (0, 10, 20%) on gas production and microbial communities to improve the performance of low-temperature anaerobic digestion systems. The results show that the addition of 30% exogenous microorganisms and a 10% volume of carbon fiber carrier led to the highest daily (128.15 mL/g VS) and cumulative (576.62 mL/g VS) methane production. This treatment effectively reduced the concentrations of COD and organic acid, in addition to stabilizing the pH of the system. High-throughput sequencing analysis revealed that the dominant bacteria under these conditions were Acidobacteria and Firmicutes and the dominant archaea were Candidatus_Udaeobacter and Methanobacterium. While the abundance of microorganisms that metabolize organic acids was reduced, the functional abundance of hydrogenophilic methanogenic microorganisms was increased. Therefore, the synergistic effect of Methanomicrobium bioaugmentation with carbon fiber carriers can significantly improve the performance and efficiency of low-temperature anaerobic fermentation systems.

Exploring the microbial ecosystem of Berchemia polyphylla var. leioclada: a comprehensive analysis of endophytes and rhizospheric soil microorganisms.

Endophytic and rhizospheric microorganisms associated with plants play a crucial role in plant health, pest and disease defense, and fruit yield by actively participating in the plant's adaptation to its environment. In this study, high-throughput sequencing technology was employed to analyze the community structure and diversity of endophytic and rhizospheric soil microorganisms in Berchemia polyphylla var. leioclada. The results revealed significant differences in microbial diversity and community structure between the soil and plant compartments within the same geographic region. Microbial diversity and species composition varied among different geographic locations. The dominant bacteria in plants were Cyanobacteria and Proteobacteria, with dominant genera including Methylobacterium-Methylorubrum, Escherichia-Shigella and Sphingomonas. In contrast, the dominant bacteria in soil were Proteobacteria, Acidobacteriota, and Actinobacteriota, with dominant genera such as Sphingomonas, Conexibacter and Vicinamibacteraceae, with Sphingomonas was considered core groups present in all plant and soil samples. As for fungi, the dominant phyla in both plants and soil were Ascomycota, Basidiomycota, and Mortierellomycota, with different dominant genera between the two compartments, including Fusarium, Septoria, and Mortierella, totaling 59 genera. Linear discriminant analysis at the genus level identified 102 bacterial and 54 fungal indicator taxa associated with plants and soil. Co-occurrence network analysis indicated close interactions among soil bacterial microorganisms. Functional prediction of the top 10 microbial genes revealed three bacterial metabolic pathways shared between soil and plants, while the predominant fungal metabolic types were similar between the two compartments but with varying abundances. This study elucidates the diversity and interplay of endophytic and rhizospheric microorganisms in Berchemia polyphylla var. leioclada across diverse geographical regions, providing insights crucial for the plant's conservation and development.

Bacterial Contamination in the Different Parts of Household Washing Machine: New Insights from Chengdu, Western China.

The moist and warm environment in the household washing machine provides ideal living conditions for the growth and survival of various microorganisms. However, the biodiversity of bacterial community in the different parts of washing machine from Chinese households has not been clarified. In this study, we assessed the bacterial communities in sealing strip, detergent drawer, inner drum, water filter and greywater of ten domestic washing machines quantitatively and qualitatively in Chengdu, southwestern China. The microbial cultivation results indicated that the washing machines from Chengdu had a severe microbial contamination reflected by large counts on bacteria, fungi and coliform. Furthermore, the sequencing data showed that the different parts displayed distinctive bacterial compositions. At the level of genus, the anaerobic bacteria of Caproiciproducens and Acidipropionibacterium were predominant in sealing strip. Barnesiella, Shinella and Sellimonas were detected as the characteristic bacteria in detergent drawer. The pathogens of Luteibacter and Corynebacterium at the genus level were the dominant bacteria in inner drum and water filter, respectively. The genera of Azospira, Roseococcus, Elstera and Aquicella, which belonged to the pathogenic phylum of Proteobacteria, were identified as bioindicators for the greywater. Gene function analysis on the sequencing data illustrated that the bacteria from washing machines were potentially associated with bacterial infectious diseases and antimicrobial resistance. This study shows the bacterial diversity in the different parts of washing machines, providing new clues for bacterial contamination in washing machines from Chinese households.