Community Structure Research Articles

Assessing spider community structure and ecological dynamics across urban and natural environments

AbstractThis study explores the diversity and distribution of spider populations across urban and natural‐semi natural habitats in Gongju‐si, South Korea. This study aims to investigate the ecological dynamics of spider populations across different habitat types and assess their implications for urban planning, particularly in terms of maintaining biodiversity through habitat heterogeneity and informed urban development strategies. Employing methodologies such as sweeping, manual collection, and pit‐fall traps, the research identifies 128 spider species and evaluates alpha and beta diversity, nestedness, and species interactions using advanced statistical and ecological tools. The findings indicate significant variations in spider diversity across different habitats, with urban areas exhibiting notable biodiversity despite human influences. Natural habitats, especially forests, demonstrate higher biodiversity and more intricate species interactions. Nestedness analysis reveals distinct community structures across habitats, while association rule learning highlights complex interspecies relationships. The study underscores the importance of maintaining habitat heterogeneity and incorporating ecological principles in urban planning to support biodiversity. It offers valuable insights into the roles of various habitats in ecological networks, emphasizing the necessity for balanced urban development and effective conservation strategies.

Evidence for the importance of trophically transmitted parasites and predation at the lower latitudes of species ranges.

The lack of information concerning how parasitism maps onto host geographical distributions represents a striking gap in ecological knowledge. This knowledge gap limits our understanding of a wide range of phenomena, including the consequences of climate change-induced range shifts of both hosts and parasites. To help solve this problem, we created a predictive theoretical framework and quantified latitudinal variation in parasitism by animal and protozoan parasites throughout the entire contiguous geographical ranges of four estuarine fish species. To circumvent frequent limitations in data and to permit revealing of novel biogeographical patterns, we (i) quantified parasitism at the individual host level, (ii) quantified parasite species diversity and biomass load, and (iii) tracked functionally distinct parasitic consumer strategies. Parasite diversity always increased at lower latitudes, and this pattern was largely driven by parasites using trophic transmission. Furthermore, in three of four cases, the role of fish as predator- versus prey-host for trophically transmitted parasite (TTP) species increased at lower latitudes. Parasite diversity patterns followed predictions more consistently than did biomass load, indicating that increased predation at lower latitudes may decrease observed parasite biomass load. These findings suggest a particularly strong role for TTPs and predation in community structure and dynamics at lower latitudes.

Enhancing phosphorus-solubilizing microorganism potential for alleviating plant phosphorus limitation through amino acid co-application

Phosphorus-solubilizing microorganisms (PSMs) are recognized as a sustainable ecological strategy to mitigate plant phosphorus (P) limitation. However, their efficacy in real-world production scenarios is not as consistent as observed in controlled laboratory conditions. To deepen our comprehension of PSMs in mitigating plant P limitation and evaluate the efficacy of combined amino acids (AA) and PSMs application in optimizing plant nutritional environments, we conducted a study, aiming to preliminary delineate the model of plant-microbe-soil interactions facilitated by this joint approach. Phyllostachys edulis seedlings were cultivated in phosphorus-limited soil with or without AA and PSMs application. We assessed treatment impacts on plant growth and soil nutrient conditions through plant biomass, root morphology, tissue nitrogen (N) and P content, soil N and P contents, rhizosphere microbial communities, and soil enzyme activities. Application of AA and PSMs significantly enhanced shoot growth of P. edulis seedlings, reduced root ratio, modified root morphology, increased N and P content in plant tissues, facilitated conversion of soil insoluble P to active forms, and raised total soil N, alkali-hydrolysable N, ammonium N, and nitrate content. Moreover, it influenced the structure and function of the soil microbial community. Notably, soil enzyme activities under the combined application exhibited distinctions from individual applications, demonstrating greater similarity to the treatment without AA and PSMs, which received no additional amendments. Our findings underscored the significant positive impact of the combined AA and PSMs application on P. edulis seedling growth, improving soil nutrient status, enriching plant growth-promoting rhizobacteria, and reducing soil diseases. However, plant-soil-microbe interactions induced by the combined application might differ from those observed with individual applications, necessitating further experimentation for a comprehensive understanding.

Arbuscular mycorrhizal fungi enhance drought resistance and alter microbial communities in maize rhizosphere soil

Although the benefits of inoculation with arbuscular mycorrhizal fungi (AMF) for mitigating drought stress and enhancing plant growth of host are well‐studied, our understanding of their interactions with soil attributes and rhizosphere microbial communities remains limited. In the present study, we conducted a pot experiment to explore how AMF affects maize growth, antioxidant activity, soil properties, and the rhizosphere microbial communities under drought stress. The results showed that AMF inoculation during drought stress resulted in improved maize seedling growth, significantly increasing plant biomass (42.7%), chlorophyll content (13.4%), and antioxidant capacity. It also enhanced soil nutrient availability and microbial biomass. We observed significant shifts in the structure and composition of the rhizosphere microbial community with AMF inoculation under drought conditions when compared to those under well-watered conditions. Significantly, bacterial diversity and composition showed greater sensitivity to drought stress than fungal communities. This was attributed to plants preferentially reducing the supply of carbon sources to bacterial rather than to fungal communities under drought conditions. AMF inoculation also enhanced the complexity (e.g., degree) and stability of the rhizosphere microbial ecological network, suggesting closer ecological interactions within the soil microbial community. Furthermore, bacterial diversity and richness played a more important role in soil function than those of fungal communities under drought stress, particularly with AMF inoculation. Overall, our findings suggest that AMF inoculation alters soil microbial diversity and interactions, highlighting their key roles in enhancing plant stress tolerance and mitigating the negative effects of drought on agricultural ecosystems.

Butyrate modulates gut microbiota and anti-inflammatory response in attenuating cisplatin-induced kidney injury.

In our previous research, we reported that administering probiotics Lactobacillus reuteri and Clostridium butyricum (LCs) before cisplatin treatment effectively modifies structures of the gut microbiota and restore ecological balance and significantly increases butyrate levels, a process closely associated with reducing cisplatin-induced nephrotoxicity. This study aims to investigate further whether the elevation of metabolite butyrate in the gut, promoted by probiotics LCs, can effectively mitigate the nephrotoxic effects of cisplatin and the progression of renal senescence in rats. Results show that butyrate administration significantly improved kidney function and decreased renal fibrosis in a dose-dependent manner compared to the cisplatin group. Its effects were associated with reductions in inflammatory responses, evidenced by decreased levels of key inflammatory markers, including KIM-1, MPO, NOX2, F4/80, and TGF-β1, alongside increased production of the anti-inflammatory cytokine IL-10. Furthermore, the butyrate intervention ameliorated cisplatin-induced gut microbiota dysbiosis, preserving the structure and diversity of healthy microbial communities. Specifically, we observed a decrease in the abundance of Escherichia_Shigella and Blautia, alongside an increase in the abundance of the butyrate-producing genus Roseburia. Notably, Escherichia_Shigella exhibited a positive correlation with the pro-inflammatory factor MPO, while displaying a negative correlation with the anti-inflammatory cytokine IL-10. Butyrate also attenuated the cisplatin-induced expression of senescence markers p21 and p16 in kidney tissue. It alleviated the cisplatin-increased senescence-associated beta-galactosidase activity and reactive oxygen species production in SV40 MES-13 cells. These results indicate that butyrate, derived from the gut microbiota, may exert a protective effect against cisplatin-induced kidney damage by regulating microbiota balance and anti-inflammatory effects.

Rhizosphere and Phyllosphere Microbial communities of male and female plants of Morus macroura

Plants are extensive habitats for microorganisms, and their impact on host environmental adaptability alters plant growth and nutrition’s. The interaction between plants and microorganisms directly influenced plant health and agricultural sustainability. Studying the diversity and interactions of endophytic bacteria in Morus macroura contributed to the sustainable development of M. macroura cultivation. This study used high-throughput gene sequencing to measure and analyze the relative abundance of bacteria in the rhizosphere and phyllosphere of male and female M. macroura. Results indicated significant differences in carbon, potassium, calcium, sulfur, boron, zinc, and copper levels between male and female phyllosphere. There was differential enrichment of certain bacterial communities in male and female M. macroura plants. Bacterial community analysis based on ASVs showed that M. macroura shared Proteobacteria as a dominant phylum in both male and female rhizosphere and phyllosphere. Linear discriminant indicated that Sphingosinicella and Arsenophonus were more abundant in the phyllosphere of female plants, while Hymenobacter was more abundant in the phyllosphere of male plants. RB41 was more abundant in the rhizosphere of female plants, whereas Gemmatimonas and Sphingomonas were more abundant in the rhizosphere of male plants. Redundancy analysis revealed a significant correlation between leaf Molybdenum (Mo), Magnesium (Mg), Carbon (C), and Copper (Cu) with the structure of the phyllosphere bacterial community. This study provided important insights into the relationship between M. macroura and bacterial communities, as well as the vertical transmission of bacteria within the plants.

Accumulation and structure of bacterial community during high-strength wastewater treatment using a novel BIFBBR

Accumulation and structure of bacterial community during high-strength wastewater treatment using a novel BIFBBR

Effect of biochar on the co-conversion of carbon-nitrogen and humification of kitchen waste composting process

Composting was an effective technique to treat kitchen waste into high-quality fertilizer or soil amendment. During the composting process of kitchen waste, different degradation rates of carbon and nitrogen resulted in carbon loss, nitrogen emission and low product quality. Consequently, the aim of this study was to investigate the mechanisms and effects of biochar (5%, 10% and 15%) on synergistic conversion of nitrogen and carbon and humification processes in kitchen waste composting. The findings revealed that the addition of 10% and 15% biochar prolonged the thermophilic phase (>55°C) by a minimum of three days compared to CK. Additionally, the final NH4+-N concentration in the 10% and 15% treatment groups exhibited a 66.7% reduction in comparison to the control. Besides, the 15% addition proved more efficacious in reducing the NH4+-N content. The increase in biochar facilitates the adsorption of ammonia nitrogen and influences the structure of the microbial community, especially Bacteroides and Pseudoxanthomonas, thus promoting nitrogen mineralisation and humification, which provides energy and carbon for the survival and metabolism of more microorganisms. The compost with 15% biochar exhibited higher levels of SBR1031, resulting in a 73.8% increase in the conversion of nitrogen to NO3--N compared to the control. The aforementioned behaviour facilitates a synergistic conversion of nitrogen and carbon. Therefore, the addition of biochar promotes synergistic carbon and nitrogen transformations in terms of nitrogen conservation, organic matter decomposition, microbial species and their interactions, which is essential for the production of value-added compost fertilizers.

Vertical profiles of community and activity of methanotrophs in large lake and reservoir of Southwest China

Microbial methane oxidation plays a significant role in regulating methane emissions from lakes and reservoirs. However, the differences in methane oxidation activity and methanotrophic community between lakes and reservoirs remain inadequately characterized. In this study, sediment and water samples were collected from the large shallow lake (Dianchi) and deep reservoirs (Dongfeng and Hongjiadu) located in karst area, Southwest China. The results indicated that the rates of aerobic oxidation of methane (AeOM) in lake sediment ranged from 7.1 to 27.7 μg g−1 d−1, which was higher than that in reservoirs sediment (1.92 to 11.56 μg g−1 d−1). Similarly, the average AeOM in the water column of lake (104.7 μg L−1 d−1) was much higher than that of reservoirs (46 μg L−1 d−1). The content of sediment organic carbon and dissolved inorganic carbon were important factors that influenced the rates of AeOM in sediment and water column, respectively. 16S rRNA genes sequencing revealed a higher relative abundance of methanotrophs in lake sediments compared to reservoir sediments. The dominant methanotrophic taxa in lake was Methylococcaceae (type Ib), while Methylomonadaceae (type Ia) was predominant in reservoirs. Meanwhile, anaerobic methane-oxidizing microorganisms Candidatus Methylomirabilis and Candidatus Methanoperedens were also abundant in sediments of reservoirs. However, metatranscriptomic analysis revealed that the type I methanotrophs, especially Methylobacter, was most active in the sediment of both lake and reservoir. Water depth and conductivity could be the key controlling factors of the structures of methanotrophic communities in sediment and water column, respectively. Metagenome-assembled genomes suggested that type I methanotrophs exhibited greater motility, as evidenced by a higher number of flagellar assembly genes, while type II methanotrophs demonstrated advantages in metabolic processes such as carbon, phosphorus, and methane metabolism.

Root, Nodule and Soil Bacterial Communities Associated With the Invasive Nitrogen-Fixing Lupinus polyphyllus.

Plants host microorganisms that can facilitate their success in becoming invasive. Established plant invasions might thus provide useful insights into potential changes in plant-associated microbiomes over the course of the invasion process. Here, we investigated the endophytic bacterial communities of the invasive herbaceous legume Lupinus polyphyllus, which is able to form mutualistic associations with N-fixing bacteria. More specifically, we examined the alpha diversity (observed bacterial taxa richness and Shannon diversity) and composition of bacterial communities in roots and nodules sampled from core and edge locations within 10 established invasion sites (> 10 years old) in southwestern Finland. Moreover, we compared the alpha diversity and structure of bacterial communities in the rhizosphere and bulk soil between core and edge locations within these invasion sites. We found that roots and nodules had distinctive endophytic bacterial communities, with roots having 24% higher bacterial alpha diversity (Shannon diversity) than nodules. In nodules, the dominant bacteria were assigned to the family Bradyrhizobiaceae, which includes N-fixing bacteria. Soil bacterial communities, instead, were shaped by soil type, with bulk soil hosting up to 27% higher alpha diversity (richness and Shannon diversity) than rhizosphere soil; however, there was no apparent difference in their community composition. Soil bacterial communities were only weakly associated with soil chemistry. Endophytic and soil bacterial communities did not differ between core and edge locations within the established invasions. Our findings suggest that L. polyphyllus may not induce dramatic changes in the bacterial communities with which it associates over the course of the local invasion process.

Influence mechanisms of dissolved organic matter and iron minerals on naphthalene attenuation during river infiltration

Natural attenuation of naphthalene (NAP) in riverbank filtration zones is vital for maintaining water quality and is affected by dissolved organic matter (DOM) and iron minerals. However, the effects of DOM and iron minerals on the attenuation of NAP remain unclear. In this study, the attenuation mechanisms of NAP under the influence of DOM and iron minerals were explored in a riverside source area. Field dynamic monitoring data revealed that the NAP concentration in groundwater is mainly influenced by DOM, effective bound‑iron, and the intensity of river water infiltration recharge. Column experiments indicated that DOM with α-Fe2O3 or α-FeO(OH) reduced medium permeability by 8.16 % or 6.85 %, respectively, increasing water retention time. However, they had different effects on the attenuation of NAP. The coexistence of α-Fe2O3 and DOM enhanced NAP attenuation capacity by 9.13 %–45.91 %, while α-FeO(OH) and DOM reduced it by −13.25 % to −24.13 %. These effects were attributed to changes in the medium permeability, particle size, secondary mineral formation, and microbial community structure. Specifically, α-Fe2O3 and DOM reduced medium permeability, increasing the adsorption and biodegradation reaction time of NAP, and promoted secondary mineral (FeCO3) formation, increasing the adsorption capacity of medium for NAP, while α-FeO(OH) and DOM underwent cementation, resulting in larger particles and reduced adsorption capacity for NAP. Additionally, α-FeO(OH) and DOM promoted Shewanlla growth, inhibiting NAP attenuation by competing with NAP-degrading bacteria. These findings improve the understanding of the natural attenuation of polycyclic aromatic hydrocarbons (PAHs) in riverbank filtration, offering a basis for evaluating and controlling PAH pollution risks.

Short-term continuous cropping leads to a decline in rhizosphere soil fertility by modulating the perilla root exudates

Continuous cropping obstacles are a prevalent issue in agricultural production worldwide. However, the key factors leading to these obstacles differ among various crops. This study utilized high-throughput sequencing and metabolomics to assess the community structure of microbes and the types and abundance of metabolites in rhizosphere soil after different continuous cropping years of Perilla frutescens L. Britt. (perilla). The results indicate that differential metabolites in soils of varying continuous cropping years are primarily associated with pathways for cellular lipid formation, oxidative stress responses, and energy metabolism. These findings suggest that the changes in soil composition over time are linked to specific biological processes related to lipid formation, oxidative stress, and energy metabolism. The relative abundance of beneficial bacteria in the soil, such as Sphingomonas, Gemmatimonas, and Blastococcus, decreased significantly (p < 0.05), while harmful fungi, such as Neocosmospora and Didymella, increased in response to the increase in continuous cropping years (p < 0.05). The symbiotic network between bacteria and fungi has become less dense and stable after continuous cropping. Enzymatic activities in rhizosphere soil decreased significantly (p < 0.05). Soil organic matter, total nitrogen, total phosphorus, total potassium, available phosphorus, and available potassium declined significantly (p < 0.05). Pearson correlation analysis identified 10 differential secondary metabolites that were closely related to the relative abundance of key microorganisms. Among them, cinnamic acid and flavonoid compounds are key factors leading to changes in microbial diversity, and they can regulate the microorganisms-soil- plants interactions. In summary, this study provides a novel scientific explanation for how continuous cropping can reduce soil fertility and a theoretical basis for subsequent cultivation strategies of perilla.

The role of the proteosurfaceome and exoproteome in bacterial coaggregation.

Bacterial coaggregation is a critical process in multispecies biofilm formation, driven by specific molecular interactions that facilitate the adhesion and aggregation of bacterial cells. These interactions are essential for the development and persistence of complex microbial communities. This review provides a comprehensive analysis of the roles of the proteosurfaceome and exoproteome in bacterial coaggregation. The proteosurfaceome, comprising surface-bound molecules such as adhesins, drives species-specific interactions crucial for partner recognition and adhesion. In parallel, the exoproteome, particularly extracellular polymeric substances (EPS), enhances aggregate stability by reinforcing structural integrity and facilitating intercellular communication, although its direct role in coaggregation remains to be fully clarified. By integrating these perspectives, this review aims to elucidate how the proteosurfaceome and exoproteome influence bacterial coaggregation, offering insights into their combined impact on microbial community structure and function. Furthermore, we highlight existing knowledge gaps and propose directions for future research.

Impact and mechanism of polyethylene terephthalate microplastics with different particle sizes on sludge anaerobic digestion.

Municipal wastewater treatment plants (WWTPs) are important sinks for microplastics, and the vast majority of microplastics entering WWTPs are trapped in residual sludge. In order to investigate the effect of microplastics on anaerobic digestion of sludge, polyethylene terephthalate (PET) microplastics with common particle size and physical aging were selected to conduct a comparative study. Regardless of aging, the addition of 300 and 500 μm PET microplastics inhibited methane production, with their cumulative methane production reduced by 11.3-24.9% compared to the control group. In contrast, when 100 μm microplastics were added, the raw PET promoted methane production, yielding 337 L CH4/kg VS, while the aged experimental group showed similar yields to the control group. For the 800 μm microplastics treatment group, aged microplastics facilitated methane production while raw microplastics inhibited it, with methane production of 91.0% and 111% of the control group, respectively. The effects were also investigated by model fitting, stage discussion, and microbial community structure analysis. The results discovered that the main rate-limiting steps of adding microplastics with smaller or larger particle sizes (100, 800 μm) to methane production were solubilization and hydrolysis, while the main rate-limiting step of microplastics with medium particle sizes (300, 500 μm) was methanogenesis. Physically aged PET microplastics with smaller or larger sizes showed a more significant effect on methane production. Furthermore, PET microplastics altered the microbial community structure, shifting methanogens from acetotrophic pathways to hydrotrophic pathways. This study offers new insights into the performance analysis of sludge anaerobic digestion in practical WWTPs.

Macrofauna community structure and population dynamics in the Flemish Bank region: assessing long-term change in the Anthropocene

Macrofauna community structure and population dynamics in the Flemish Bank region: assessing long-term change in the Anthropocene

Top-down predators shape soil bacterial community composition while bottom-up nutrients drive bacterial abundance

Although the top-down and bottom-up concept in microbial food-webs has been a primary interest in ecology, less is still known about it in soil ecosystems. Protists are the primary top-down predators of bacterial communities, altering their compositions, while the bottom-up resources are the primary factors limiting bacterial growth. Here, we hypothesized that the top-down predators modulate soil bacterial community composition, while the bottom-up nutrients control the bacterial growth and population. To precisely control nutrient levels, we used an inert soil substitute consisting of a combination of calcined clay and sand. Nutrients equivalent to the reference paddy field soil were added to microcosms as a control treatment. To investigate the effects of C, N, and P, six additional bottom-up treatments in the absence and double amounts of the nutrients were prepared. Four top-down treatments (no protist addition, Acanthamoeba castellanii, Vermamoeba vermiformis, and Heteromita globosa) were set up for each bottom-up treatment. A total of 252 microcosms under 28 treatments were incubated. Bacterial communities were analyzed using high-throughput sequencing and real-time PCR in the 1st, 3rd, and 5th weeks. The results revealed that the top-down predators significantly altered the bacterial community composition, and the bacterial population was predominantly controlled by the bottom-up nutrients. Analysis of absolute abundance data demonstrated that both top-down and bottom-up factors shaped the bacterial community structure (community composition and population). Random forest analysis classified the amplicon sequence variants associated with the treatments, showing that mostly similar families were affected by both bottom-up and top-down factors. In conclusion, the results of this study fully supported our hypothesis that top-down predators alter community composition, while bottom-up factors influence bacterial population dynamics.

The Microbial Co-infection Interaction Network in Apical Periodontitis with Sinus Tracts

This study aims to characterize the bacterial co-occurrence features and potential interactions associated with the presence of sinus tracts in apical periodontitis in a Chinese population by using 16S rRNA next-generation sequencing (NGS). Thirty-one samples from twenty-six patients were collected from root canals. Following the extraction of the bacterial DNA, the V3-V4 hypervariable regions of the 16S rRNA gene were sequenced. Compositional diversity, prominent taxa and co-occurrence network analysis were compared according to the presence or absence of sinus tracts. The overall microbiota in two groups exhibited distinguished patterns. Actinomyces dominated in samples with sinus tracts while Prevotella was the most abundant in samples without sinus tracts. The major pathogens in sinus tracts exhibited a complex co-occurrence network, in which Pseudomonas formed a distinctive cluster with enriched abundance, and the extensive correlations centered on Desulfovibrio and Pseudoramibacter may suggest novel dependencies. In the network without sinus tracts, the Bacteroidetes and Firmicutes taxa presented close internal associations. The sequencing results confirmed the complexity of the microbiota in AP. The presence of sinus tracts was associated with distinctive infective patterns and complicated microbial co-infection interaction networks. Further investigations should be adopted to elucidate the relationship between the novel interactions and disease progression. Exploring the microbial interactions leads to a better understanding of etiology of apical periodontitis. Utilizing next generation sequencing techniques, our research uncovered the bacterial community structure and observed co-infection networks associated with sinus tracts, providing potential insights for prognosis prediction and targeted therapeutics of persistent inflammation.

Light grazing increased but heavy grazing decreased the abundance and family richness of soil arthropods community in an alpine grassland in the Qinghai Lake Basin.

Soil arthropods are important biological components of the soil food web, which are highly sensitive to environmental disturbances and can rapidly respond to changes in the external environment, then reflect the stability and health of the soil ecosystem. We investigated the community structure of soil arthropod and their responses to grazing intensity along soil depth (from topsoil to subsoil) through a manipulated grazing treatment with four intensity levels (no grazing, light grazing, moderate grazing and heavy grazing) in an alpine grassland in the Qinghai Lake basin. The results showed that: (1) Collembola was the dominant group in the experimental site. (2) Nearly two-thirds of the individuals were distributed in the topsoil (0-10 cm), and grazing did not cause soil arthropods to migrate from the topsoil to deeper soil layers. (3) Light grazing had a positive effect on increasing the individual number, family richness and diversity of soil arthropods, while heavy grazing had the opposite effect, exerting a negative impact on the soil arthropod community. (4) When the grazing intensity did not exceed moderate grazing (i.e. stocking rate of 3.86 Tibetan sheep·hm-2), grazing would have a positive effect on the soil arthropod community. In summary, light grazing is the intensity of disturbance that has a positive effect on the soil arthropod community in this region. This study not only revealed the impact of grazing on the community structure of soil arthropods but also aided in assessing the potential effects of grazing activities on the stability of soil ecosystems, providing scientific evidence for the sustainable management of alpine grasslands.

From thaw till fall: Interacting hydrology, carbon cycle, and greenhouse gas dynamics in a subarctic stream-lake continuum.

Carbon-water interaction studies between aquatic and terrestrial ecosystems are especially needed today in Arctic and Boreal regions, as they are facing drastic warming and precipitation shifts. Despite the importance of streams in the carbon cycle, northern stream-based studies are scarce, owing to a lack of measurements throughout the north, and possibly skewing global greenhouse gas estimates. We used a combination of multiscale measurements to quantify water sources (H2O isotope proxies), carbon availability (dissolved in/organic carbon concentrations) and quality (water absorbance, SUVA254 -index), microbial community structure (16S rRNA sequencing), and carbon dioxide (CO2) and methane (CH4) fluxes and concentrations. Our study site comprises a groundwater-influenced and peatland-dominated second-order stream, along with its adjacent lake inlet located in Northern Finland. Sampling was conducted three times during the summer of 2019 at 21 locations along the stream-lake continuum. Temporal and spatial shifts in water sources altered carbon characteristics, with CH4 concentrations being the key environmental factor shaping the microbial communities, overriding the influence of dissolved organic carbon amount and quality. The prevalence of methanotrophic bacteria highlighted the importance of CH4 as a carbon source and the methanotrophic groups as drivers of the CH4/CO2 source-sink attributes of subarctic stream systems. Our results highlight the value of integrated hydrological, biogeochemical, and microbiological measures to resolve the biocomplexity of carbon-water interactions in northern headwater catchments.

Differences in bacterial community structure and volatile flavor substance of industrial-scale tiger skin chicken feet stored at air packaging and vacuum packaging

The aim of this study was to investigate the differences of quality indexes, bacterial community and volatile organic compounds (VOCs) of industrial-scale tiger skin chicken feet (TSCF) under air packaging (AP) and vacuum packaging (VP). The results showed that the pH, total volatile basic nitrogen, total number of bacterial colony, and sensory scores in VP group changed less than those in AP group during the storage period. Different packaging conditions also had significant effects on bacterial community at the genus levels. Weissella and Lactococcus was the dominant genus in AP group, while Lactiplantibacillus and Pediococcus also had the large proportions in addition to Weissella and Lactococcus in VP group, which also led to the differences in VOCs between the two groups. Several VOCs could be used as potential spoilage indicators, including 2-octanone, ethanol, ethyl acetate and acetic acid in AP-stored TSCF, and 2-octanone, ethanol, ethyl acetate, 2-butyl-1-octanol, (R)-2-butanol, (E)-3-hexenoic acid and 2-butanone in VP-stored TSCF. Correlation analysis showed that these predominance spoilage microorganisms were significantly correlated with these VOCs of TSCF during the storage period. This study can provide a theoretical basis for understanding of the spoilage process of TSCF.