Temporal Dynamics Of Microbial Communities Research Articles

Seasonal dynamics of the microbial community in a strong-flavor baijiu fermentation.

The microbial community plays a crucial role in Chinese strong-flavor baijiu (SFB) fermentation. However, the seasonal dynamics of the microbial community in the SFB fermentation system and its contribution to the unique flavor of SFB have not been fully elucidated. In this study, we investigated the seasonal dynamics of the microbial community through 16S rRNA and ITS gene sequencing. The results revealed significant temporal dynamics of microbial communities and environmental variables throughout the four seasons. The influence of seasons on fungal communities was found to be more significant than on bacterial communities. The diversity of bacteria was higher during the winter and summer, whereas fungal diversity was more prominent in summer and autumn. Stochastic processes maintained their dominance in microbial assembly throughout all four seasons but the significance of heterogeneous selection increased during summer for both bacteria and fungi, whereas homogeneous selection became more pronounced during winter for fungi. The pH and environmental temperature were important drivers of microbial community assembly across different seasons, primarily impacting the core genera responsible for the production of major volatile flavor compounds (VFCs), especially ethyl caproate. These findings provide new insights into the impact of seasons on microbial communities and hold promise for improving the quality-control measures for SFB brewed in different seasons. © 2024 Society of Chemical Industry.

Temporal Variation of Methanogenic Microbial Community in Palm Oil Mill Effluent (POME) Anaerobic Digester

Palm Oil Mill Effluents (POME) serve as suitable substrates for methane gas production through anaerobic digestion. This process relies on a complex microbial community that plays a critical role in ensuring stable anaerobic digester operation and efficient biogas production. Among these microorganisms, methanogenic archaea are pivotal in methane generation by utilizing diverse substrates under anoxic conditions. However, the knowledge of the microbial communities, particularly those involved in methane production in POME anaerobic sludge at different time intervals, remains limited. This study aims to uncover temporal variations in microbial communities, including diversity, composition, and structure, within POME anaerobic sludge, specifically focusing on the methanogenic archaea community. The temporal dynamics of microbial communities in the eighteen POME anaerobic sludge samples collected from a palm oil mill were investigated through 16S rRNA amplicon sequencing. The results reveal consistent microbial community diversity in POME anaerobic sludge over the study periods. Then, the sequencing also showed that Bacillota (26.9 ± 3.3%), Bacteroidota (20.2 ± 5.3%), and Chloroflexota (15.0% ± 6.3%) were the dominant bacterial phyla in POME anaerobic sludge across different time frames. Concurrently, Halobacteriota (5.9 ± 2.8%), Methanobacteriota (2.5 ± 0.6%), and Nanoarchaeota (2.3 ± 1.2%) were the primary archaeal phyla identified in anaerobic sludge at various time intervals. Furthermore, amplicon sequencing revealed the presence of two methanogenic archaea genera, Methanothrix and Methanobacterium, associated with acetoclastic and hydrogenotrophic methanogenesis, respectively. These findings suggest that acetoclastic and hydrogenotrophic methanogenesis pathways are the primary contributors to methane production in the POME anaerobic digestion process.

Effects of deterministic assembly of communities caused by global warming on coexistence patterns and ecosystem functions

Seasonal rhythms in biological and ecological dynamics are fundamental in regulating the structuring of microbial communities. Evaluating the seasonal rhythms of microorganisms in response to climate change could provide information on their variability and stability over longer timescales (>20-year). However, information on temporal variability in microorganism responses to medium- and long-term global warming is limited. In this study, we aimed to elucidate the temporal dynamics of microbial communities in response to global warming; to this end, we integrated data on the maintenance of species diversity, community composition, temporal turnover rates (v), and community assembly process in two typical ecosystems (meadows and shrub habitat) on the Qinghai-Tibet Plateau. Our results showed that 21 years of global warming would increase the importance of the deterministic process for microorganisms in both ecosystems across all seasons (R2 of grassland (GL) control: 0.524, R2 of GL warming: 0.467; R2 of shrubland (SL) control: 0.556, R2 of SL warming: 0.543), reducing species diversity and altering community composition. Due to environmental filtration pressure from 21 years of warming, the low turnover rate (v of warming: −3.13/-2.00, v of control: −2.44/−1.48) of soil microorganisms reduces the resistance and resilience of ecological communities, which could lead to higher community similarity and more clustered taxonomic assemblages occurring across years. Changes to temperature might increase selection pressure on specialist taxa, which directly causes dominant species (v of warming: −1.63, v of control: −2.49) primarily comprising these taxa to be more strongly impacted by changing temperature than conditionally (v of warming: −1.47, v of control: −1.75) or always rare taxa (v of warming: −0.57, v of control: −1.33). Evaluation of the seasonal rhythms of microorganisms in response to global warming revealed that the variability and stability of different microbial communities in different habitats had dissimilar biological and ecological performances when challenged with an external disturbance. The balance of competition and cooperation, because of environmental selection, also influenced ecosystem function in complex terrestrial ecosystems. Overall, our study enriches the limited information on the temporal variability in microorganism responses to 21 years of global warming, and provides a scientific basis for evaluating the impact of climate warming on the temporal stability of soil ecosystems.

Sampling period and disease severity of bacterial wilt significantly affected the bacterial community structure and functional prediction in the sesame rhizosphere soil

The changes in the structure and function of bacterial communities present in the rhizosphere soils are of great significance for disease control in sesame, but it remains unclear to date. The present study explored the effects of five sampling periods (F0, day 0 after the first flowering; F11; F21; F32; F48) and three disease severities (H0, healthy; D5, moderate diseased; D9, serious diseased) on the structure and function using high throughput sequencing. The results indicated that the values of the Obs, Shannon, Chao1, and ACE first increased and then decreased in the D5 and D9 groups as plants matured, while an increasing trend was observed in the H0 group. The relative abundances of Actinobacteria and Proteobacteria demonstrated a trend from lower values to increased values and then again to lower values in the later sampling period. In the D9 group, Ralstonia experienced a significant 2.15-fold increase during the F0 period, while Gemmatimonas and Streptomyces demonstrated significant increases of 0.65 and 0.30 percentage points, respectively, in the D9 group during the F11 and F21 periods compared to H0. The predominant phyla in the H0 group during the F0 and F11 periods were p_Verrucomicrobiota and p_Firmicutes, respectively. In the D5 group during the F11 period, there were notable increases in xenobiotics biodegradation and metabolism (7.72%) and amino acid metabolism (0.80%) compared to H0, while nucleotide metabolism, replication and repair, and translation experienced significant decreases of 1.85%, 2.16%, and 1.64%, respectively. This critical period preceding the final flowering influenced the structure and function of bacterial communities in the sesame rhizosphere soil. The available potassium and boron exhibited a significant negative correlation with the phyla Proteobacteria and Crenarchaeota, while these phyla were significantly positively correlated with the genera Sphingomonas, Ramlibacter, and Gemmatimonas in the rhizosphere soil, and Carbohydrate_Metabolism and Cell_Motivity of the bacterial functions. The findings contribute to the understanding of the temporal dynamics of microbial communities and their functions in sesame rhizosphere soil, and their response mechanisms to bacterial wilt severity.

The effects of flow field on the succession of the microbial community on artificial reefs

The flow field is one of the most important external conditions affecting the development of biofouling community on artificial reefs (ARs), especially the microbial community. In this article, we investigated the temporal dynamics of microbial communities between the stoss side and the lee side of ARs. The results showed that the composition and structure of microbial and macrobenthic communities between the stoss side and the lee side both presented obvious temporal variations. Microbial diversity and richness were higher on the stoss side than that on the lee side. There was a greater impact on bacterial and archaeal communities on temporal scale compared to that on micro-spatial scale, which was not suitable for the fungal community. The organism biomass, abundance and coverage of macrobenthic community on the lee side were higher than those on the stoss side, and the microbial diversity on the stoss side increased significantly with the organism coverage.

Insight into the temporal dynamics of microbial succession and ecology mechanisms in biological activated carbon tanks

Biological activated carbon (BAC) has long been applied in China to guarantee water quality and to achieve drinking water regulations. However, a knowledge gap remains regarding the temporal dynamics of microbial communities, particularly microbe-based assembly and co-occurrence patterns. Accordingly, this study investigated the evolution of BAC microbial communities using a pilot-scale system and examined by multivariate ecological combined with high-throughput Illumina sequencing and statistical methods. The results showed that BAC microbial diversity reached its peak in 2 years and declined thereafter. Microbial communities composition was accompanied by significant temporal evolution in the BAC biofilm. Deterministic processes gained in importance along with time, especially homogeneous selection which contributed 59.09 %–75.63 % to the community assembly in 8-yr, 9-yr, and 10-yr BAC. According to co-occurrence network analysis, microbial networks have more unstable structures over time, as evidenced by higher modularity, heightened connectivity, and fewer keystones. Moreover, the interaction between microbial taxa tended to have a higher proportion of competitive relationships during the operation of the BAC tank, ranging from 13.51 % to 76.35 %. Based on these dynamic ecological processes, microbial community succession in BAC biofilm might undergo four phases: community establishment (Years 0–2); community stability (Years 2–5); community quasi-degradation (Years 5–8); community degradation (Years 8–10). The performance of BAC was greatly influenced by community development, and contaminant removal gradually decreased as community succession proceeded. These results add to our knowledge of microbial ecology and provide the basis for further research into microbial communities' regulation strategies in BAC tanks.

Microplastic-associated biofilm in an intensive mariculture pond: Temporal dynamics of microbial communities, extracellular polymeric substances and impacts on microplastics properties

Microplastics (MPs, plastic particles <5 mm) have been recognised as a novel ecological niche in the aquatic environments. Biofilm as a reservoir for opportunistic bacterial pathogens and MPs prevalence in the intensive mariculture could pose potential threats to the safety of cultured species. However, possible ecological consequences of biofilm colonising mariculture-associated MPs, such as effects on MPs fate, potential pathogens, and implications of extracellular polymeric substances (EPS) in biogeochemical cycles, are still unclear. The main objective of the present study was to investigate biota-MPs-EPS interactions in a mariculture pond. Polyethylene (PE) and polystyrene (PS), and biodegradable polylactic acid (PLA), with a mean size of ~1 mm, were exposed in situ to the pond after shrimp postlarvae were stocked. Several methods, including microscopy, spectroscopy, and high-throughput sequencing, were employed to investigate biota-MPs-EPS interactions with the shrimp growth. Genotypic data revealed distinct differences in bacterial compositions between MPs and pond water. Dissimilarities of microorganism compositions on MPs increased significantly as a function of exposure time, while microorganism abundance on MPs was co-determined by both exposure time and MPs type. Potential opportunistic pathogens, including Vibrio, Enterobacteriaceae and Tenacibaculum, were found in the mariculture-associated MPs biofilm. The attachment of predominant EPS (including proteins, polysaccharides and lipids) to MPs appeared to be reversible. Among these MPs, PE with large specific surface area exhibited higher biomass and EPS content than the other two MPs with smooth surface. Consequently, pronounced variations in physicochemical properties were observed for PE. This was the first study providing in-depth insights into the interactions of MPs-biota-EPS in the aquatic environment, which was beneficial to evaluate the seafood safety concern posed by MPs exposure to intensive mariculture. Given that the presence of pathogens on MPs surfaces and MPs covered by biofilm may raise a concern about the hazard potential of mariculture-associated MPs, efficient policies and technologies should be adopted to reduce MPs in aquaculture for facilitating sustainable and healthy development.

Long-Term Eutrophication and Dynamics of Bloom-Forming Microbial Communities during Summer HAB in Large Arctic Lake

Harmful algal blooms (HABs) in arctic lakes are recent phenomena. In our study, we performed a long-term analysis (1990–2017) of the eutrophication of Lake Imandra, a large subarctic lake, and explored the biodiversity of bloom-forming microorganisms of a 2017 summer HAB. We performed a 16Sr rRNA metabarcoding study of microbial communities, analysed the associations between N, P, C, and chlorophyll concentrations in the lake water, and developed models for the prediction of HABs based on total P concentration. We have demonstrated that blooms in Lake Imandra occur outside of optimal Redfield ratios and have a nonlinear association with P concentrations. We found that recent summer HABs in a lake occur as simultaneous blooms of a diatom Aulacoseira sp. and cyanobacteria Dolichospermum sp. We have studied the temporal dynamics of microbial communities during the bloom and performed an analysis of the publicly available Dolichospermum genomes to outline potential genetic mechanisms beneath simultaneous blooming. We found genetic traits requisite for diatom-diazotroph associations, which may lay beneath the simultaneous blooming of Aulacoseira sp. and Dolichospermum sp. in Lake Imandra. Both groups of organisms have the ability to store nutrients and form a dormant stage. All of these factors will ensure the further development of the HABs in Lake Imandra and the dispersal of these bloom-forming species to neighboring lakes.

Spatial and Temporal Distribution of Soil Microbial Properties in Two Shrub Intercrop Systems of the Sahel

The Sahel is an ecologically vulnerable region where increasing populations with a concurrent increase in agricultural intensity has degraded soils. Agroforestry offers an approach to remediate these landscapes. A largely unrecognized agroforestry resource in the Sahel are the native shrubs, Piliostigma reticulatum, and Guiera senegalensis that to varying degrees already coexist with row crops. These shrubs improve soil quality, redistribute water from the deep soil to the surface (hydraulic lift), and can improve crop growth. However, little information is available on whether these shrubs affect spatial and temporal dynamics of microbial communities. Therefore, the objective of this study was to determine microbial composition and activity in the wet and dry seasons of soil in the: shrub rhizosphere (RhizS), inter-root zone (IntrS), and outside the influence of shrub soil (OutS) for both G. senegalensis and P. reticulatum in Senegal. A 3 × 2 factorial field experiment was imposed at two locations (490 and 700 mm annual rainfall with G. senegalensis and P. reticulatum, respectively), that had the soil sampling treatments of three locations (RhizS, IntrS, and OutS) and two seasons (wet and dry). Soils were analyzed for: microbial diversity (DGGE with bacterial 16S or fungal 28S rRNA gene sequences phospholipids fatty acid, PLFA); enzyme activities; microbial biomass carbon (MBC); and nitrogen (N) mineralization potential. For the DGGE profiling, the bacterial community responded more to the rhizosphere effect, whereas, the fungal community was more sensitive to season. PLFA, MBC, enzyme activities and inorganic N were significantly higher in both seasons for the RhizS. The presence of shrubs maintained rhizosphere microbial communities and activity during the dry season. This represents a paradigm shift for semi-arid environments where logically it would be expected to have no microbial activity in the extended dry season. In contrast this study has shown this is not the case that rather the presence of shrub roots maintained the microbial community in the dry season most likely due to hydraulic lift and root exudates. This has implications when these shrubs are in cropped fields in that decomposition and mineralization of nutrients can proceed in the dry season. Thus, enabling accumulation of plant available nutrients during the dry season for uptake by crops in the rainy season.

Temporal Dynamics of Rhizobacteria Found in Pequin Pepper, Soybean, and Orange Trees Growing in a Semi-arid Ecosystem

Harsh environmental conditions in drylands force plants and their associated microbial communities to adapt to abiotic stresses. In semi-arid environments, climatic conditions and poor agricultural management have a strong impact on plant yield and thus, enhancing soil fertility by means of beneficial microorganisms such as plant growth-promoting rhizobacteria (PGPR) has been proposed as part of sustainable agricultural management. As drylands will increase due to climate change, studying microbial community dynamics of crops under such conditions is crucial as it might favor rhizobacteria adapted to drought. While the microbiome of many native dryland crops has been characterized, the microbial community composition from non-native crops under semi-arid environmental conditions is understudied. Thus, the aim of this study was to characterize the bacterial community associated with the roots of three crops with different growth cycles, cultivated in the same semi-arid environment, to understand their microbial community composition during the season with the highest temperature in northeast Mexico. We performed high throughput sequencing of the V3-V4 region of the 16S rRNA gene from root samples of Pequin pepper, soybean and orange trees. Classified taxa were evaluated according to crop, sampling time and climatologic parameters. Our findings revealed that changes in temporal dynamics of microbial communities correlate with environmental temperature. Moreover, the microbial community of pepper was more diverse and differed from that of soybean and orange. Regarding PGPR, 47.6% of the genera were shared among crops with a high relative abundance of Bacillus, but we also detected crop-specific microbial associations where Serratia was specific to orange trees and Rhodobacter to pepper. When analyzing PGPR in correlation to climatologic parameters, Bacillus was found to thrive under lower precipitation rates, higher temperatures and higher evaporation rates in pepper and orange. In contrast, some PGPR commonly used in commercial biofertilizers such as Rhizobium and Azospirillum were affected by high temperatures. This study provides a better understanding of the rhizobacterial assemblies of economically relevant crops grown under a semi-arid environment.

Mothers of Preterm Infants Have Individualized Breast Milk Microbiota that Changes Temporally Based on Maternal Characteristics

Mother's milk contains complex microbial communities thought to be important for colonizing a preterm infant's gastrointestinal tract. However, little is known about the microbiota in the preterm mother's milk and factors influencing its composition. We characterized the temporal dynamics of microbial communities in 490 breast milk samples from 86 mothers of preterm infants (born <1,250g) over the first 8weeks postpartum. Highly individualized microbial communities were identified in each mother's milk that changed temporally with notable alterations in predicted microbial functions. However, pre-pregnancy BMI, delivery mode, and antibiotics were associated with changes in these microbial dynamics. Individual classes of antibiotics and their duration of exposure during prenatal and postpartum periods showed unique relationships with microbial taxa abundance and diversity in mother's milk. These results highlight the temporal complexity of the preterm mother's milk microbiota and its relationship with maternal characteristics as well as the importance of discussing antibiotic stewardship for mothers.

Estimating relative biomasses of organisms in microbiota using \u201cphylopeptidomics\u201d

BackgroundThere is an important need for the development of fast and robust methods to quantify the diversity and temporal dynamics of microbial communities in complex environmental samples. Because tandem mass spectrometry allows rapid inspection of protein content, metaproteomics is increasingly used for the phenotypic analysis of microbiota across many fields, including biotechnology, environmental ecology, and medicine.ResultsHere, we present a new method for identifying the biomass contribution of any given organism based on a signature describing the number of peptide sequences shared with all other organisms, calculated by mathematical modeling and phylogenetic relationships. This so-called “phylopeptidomics” principle allows for the calculation of the relative ratios of peptide-specified taxa by the linear combination of such signatures applied to an experimental metaproteomic dataset. We illustrate its efficiency using artificial mixtures of two closely related pathogens of clinical interest, and with more complex microbiota models.ConclusionsThis approach paves the way to a new vision of taxonomic changes and accurate label-free quantitative metaproteomics for fine-tuned functional characterization.AZqEX-w-2DoMcPFXCsnk2VVideo abstract

Soil microbial succession with soil development since costal reclamation

Large area of tidal flats in Chinese coast has been reclaimed to support agriculture and urban development because of rapid population and economic growth. Knowledge of soil development mechanisms is essential for efficient management of land resources in coastal zone. So far, most studies have focused on consequences of soil physico-chemical properties on soil quality evolution after tideland reclamation for cultivation. However, a large part of soil bioprocess drives many soil processes and the effect of organism composition on the performance of soil development remains unclear. In this study, temporal dynamics of microbial communities were investigated by DNA metabarcoding to delineate the patterns and drivers of soil microbial succession along a chronosequence since reclamation from tidal flat in the Yangtze River Delta of China. Soil physicochemical properties and soil microbial structure shifted significantly, indicating the development of soil fertility. Both soil bacterial and eukaryotic diversities significantly increased after about 60 years of agricultural reclamation. Succession of bacterial structure was linked with significant decrease in the relative abundance of Proteobacteria and increase in the relative abundance of Acidobacteria. Succession of eukaryote structure exhibited significant decrease in the relative abundance of Metazoa and Ochrophyta and increase in the relative abundance of Fungi. Further analysis indicated that temporal and environmental filters act together to structure soil microbial communities across long-term cultivation. An orderly growth of soil microbial community and diversity with respect to soil fertility development has been verified. The succession of soil microbial community and diversity towards higher soil quality after the tidal flat reclamation, which was mainly correlated with soil physicochemical changes with time.

Microbial Community Dynamics During Lake Ice Freezing

Many freshwater environments experience dramatic seasonal changes with some systems remaining ice-covered for most of the winter. Freshwater systems are also highly sensitive to environmental change. However, little is known about changes in microbial abundance and community composition during lake ice formation and times of persistent ice cover. The goal of this study is to characterize temporal dynamics of microbial communities during ice formation and persistent ice cover. Samples were collected in triplicate, five days per week from surface water in the Keweenaw Waterway between November and April. Environmental conditions along with microbial abundance and microbial community composition was determined. Distinct community composition was found between ice-free and ice-covered time periods with significantly different community composition between months. The microbial community underwent dramatic shifts in microbial abundance and diversity during the transitions into and out of ice cover. The richness of the microbial community increased during times of ice cover. Relatives of microbes involved in nitrogen cycling bloomed during times of ice cover as sequences related to known nitrifying taxa were significantly enriched during ice cover. These results help to elucidate how microbial abundance and diversity change over drastic seasonal transitions and how ice cover may affect microbial abundance and diversity.

Diurnal Temperature Variation and Plants Drive Latitudinal Patterns in Seasonal Dynamics of Soil Microbial Community.

Seasonality, an exogenous driver, motivates the biological and ecological temporal dynamics of animal and plant communities. Underexplored microbial temporal endogenous dynamics hinders the prediction of microbial response to climate change. To elucidate temporal dynamics of microbial communities, temporal turnover rates, phylogenetic relatedness, and species interactions were integrated to compare those of a series of forest ecosystems along latitudinal gradients. The seasonal turnover rhythm of microbial communities, estimated by the slope (w value) of similarity-time decay relationship, was spatially structured across the latitudinal gradient, which may be caused by a mixture of both diurnal temperature variation and seasonal patterns of plants. Statistical analyses revealed that diurnal temperature variation instead of average temperature imposed a positive and considerable effect alone and also jointly with plants. Due to higher diurnal temperature variation with more climatic niches, microbial communities might evolutionarily adapt into more dispersed phylogenetic assembly based on the standardized effect size of MNTD metric, and ecologically form higher community resistance and resiliency with stronger network interactions among species. Archaea and the bacterial groups of Chloroflexi, Alphaproteobacteria, and Deltaproteobacteria were sensitive to diurnal temperature variation with greater turnover rates at higher latitudes, indicating that greater diurnal temperature fluctuation imposes stronger selective pressure on thermal specialists, because bacteria and archaea, single-celled organisms, have extreme short generation period compared to animal and plant. Our findings thus illustrate that the dynamics of microbial community and species interactions are crucial to assess ecosystem stability to climate variations in an increased climatic variability era.

Flood pulse regulation of bacterioplankton community composition in an Amazonian floodplain lake

Abstract Understanding spatial and temporal dynamics of microbial communities is a central challenge in microbial ecology since microorganisms play a key role in ecosystem functioning and biogeochemical cycles. Amazonian aquatic systems comprise a dynamic mosaic of heterogeneous habits but are understudied and there is limited information about the mechanisms that shape bacterial community composition (BCC). There is a consensus that environmental selection (species sorting) and dispersal processes (source–sink dynamics) act in concert to shape the composition of these communities, but the relative importance of each mechanism may vary dramatically through time and between systems. Applying 16S rRNA gene amplicon high‐throughput sequencing, we studied factors and processes that modulate BCC in an Amazonian floodplain lake and used source‐tracking models to trace the main dispersal sources of microorganisms in the whole floodplain system during a full hydrological cycle. Our source‐tracking models indicated that dispersal processes were predominant, explaining most of the BCC variability throughout the study period. We observed more sources contributing to the sink community during the falling water than rising water period, when contributions from the Solimões River dominated. There was a clear seasonal pattern in BCC, closely related to environmental variables, suggesting that the successful establishment of dispersing bacteria also depends on environmental filtering that is linked to water flow. In summary, source–sink dynamics and species sorting were strongly affected by water exchange and connectivity with the main river that varied throughout the flood pulse cycle. Our results demonstrated the influence of lateral transport and temporal dynamics on BCC in Amazonian floodplain lakes that could ultimately impact regional carbon budgets and biogeochemical cycles.

Long-term spatial and temporal microbial community dynamics in a large-scale drinking water distribution system with multiple disinfectant regimes

Long-term spatial-temporal investigations of microbial dynamics in full-scale drinking water distribution systems are scarce. These investigations can reveal the process, infrastructure, and environmental factors that influence the microbial community, offering opportunities to re-think microbial management in drinking water systems. Often, these insights are missed or are unreliable in short-term studies, which are impacted by stochastic variabilities inherent to large full-scale systems. In this two-year study, we investigated the spatial and temporal dynamics of the microbial community in a large, full scale South African drinking water distribution system that uses three successive disinfection strategies (i.e. chlorination, chloramination and hypochlorination). Monthly bulk water samples were collected from the outlet of the treatment plant and from 17 points in the distribution system spanning nearly 150 km and the bacterial community composition was characterised by Illumina MiSeq sequencing of the V4 hypervariable region of the 16S rRNA gene. Like previous studies, Alpha- and Betaproteobacteria dominated the drinking water bacterial communities, with an increase in Betaproteobacteria post-chloramination. In contrast with previous reports, the observed richness, diversity, and evenness of the bacterial communities were higher in the winter months as opposed to the summer months in this study. In addition to temperature effects, the seasonal variations were also likely to be influenced by changes in average water age in the distribution system and corresponding changes in disinfectant residual concentrations. Spatial dynamics of the bacterial communities indicated distance decay, with bacterial communities becoming increasingly dissimilar with increasing distance between sampling locations. These spatial effects dampened the temporal changes in the bulk water community and were the dominant factor when considering the entire distribution system. However, temporal variations were consistently stronger as compared to spatial changes at individual sampling locations and demonstrated seasonality. This study emphasises the need for long-term studies to comprehensively understand the temporal patterns that would otherwise be missed in short-term investigations. Furthermore, systematic long-term investigations are particularly critical towards determining the impact of changes in source water quality, environmental conditions, and process operations on the changes in microbial community composition in the drinking water distribution system.

The microbiota of traumatic, open fracture wounds is associated with mechanism of injury.

Open fractures are characterized by disruption of the skin and soft tissue, which allows for microbial contamination and colonization. Preventing infection-related complications of open fractures and other acute wounds remains an evolving challenge due to an incomplete understanding of how microbial colonization and contamination influence healing and outcomes. Culture-independent molecular methods are now widely used to study human-associated microbial communities without introducing culture biases. Using such approaches, the objectives of this study were to (1) define the long-term temporal microbial community dynamics of open fracture wounds and (2) examine microbial community dynamics with respect to clinical and demographic factors. Fifty-two subjects with traumatic open fracture wounds (32 blunt and 20 penetrating injuries) were enrolled prospectively and sampled longitudinally from presentation to the emergency department (ED) and at each subsequent inpatient or outpatient encounter. Specimens were collected from both the wound center and adjacent skin. Culture-independent sequencing of the 16S ribosomal RNA gene was employed to identify and characterize microbiota. Upon presentation to the ED and time points immediately following, sample collection site (wound or adjacent skin) was the most defining feature discriminating microbial profiles. Microbial composition of adjacent skin and wound center converged over time. Mechanism of injury most strongly defined the microbiota after initial convergence. Further analysis controlling for race, gender, and age revealed that mechanism of injury remained a significant discriminating feature throughout the continuum of care. We conclude that the microbial communities associated with open fracture wounds are dynamic in nature until eventual convergence with the adjacent skin community during healing, with mechanism of injury as an important feature affecting both diversity and composition of the microbiota. A more complete understanding of the factors influencing microbial contamination and/or colonization in open fractures is a critical foundation for identifying markers indicative of outcome and deciphering their respective contributions to healing and/or complication.

Treatment impacts on temporal microbial community dynamics during phytostabilization of acid-generating mine tailings in semiarid regions

Direct revegetation, or phytostabilization, is a containment strategy for contaminant metals associated with mine tailings in semiarid regions. The weathering of sulfide ore-derived tailings frequently drives acidification that inhibits plant establishment resulting in materials prone to wind and water dispersal. The specific objective of this study was to associate pyritic mine waste acidification, characterized through pore-water chemistry analysis, with dynamic changes in microbial community diversity and phylogenetic composition, and to evaluate the influence of different treatment strategies on the control of acidification dynamics. Samples were collected from a highly instrumented one-year mesocosm study that included the following treatments: 1) unamended tailings control; 2) tailings amended with 15% compost; and 3) the 15% compost-amended tailings planted with Atriplex lentiformis. Tailings samples were collected at 0, 3, 6 and 12months and pore water chemistry was monitored as an indicator of acidification and weathering processes. Results confirmed that the acidification process for pyritic mine tailings is associated with a temporal progression of bacterial and archaeal phylotypes from pH sensitive Thiobacillus and Thiomonas to communities dominated by Leptospirillum and Ferroplasma. Pore-water chemistry indicated that weathering rates were highest when Leptospirillum was most abundant. The planted treatment was most successful in disrupting the successional evolution of the Fe/S-oxidizing community. Plant establishment stimulated growth of plant-growth-promoting heterotrophic phylotypes and controlled the proliferation of lithoautotrophic Fe/S-oxidizers. The results suggest the potential for eco-engineering a microbial inoculum to stimulate plant establishment and inhibit proliferation of the most efficient Fe/S-oxidizing phylotypes.

Temporal Microbial Community Dynamics in Microbial Electrolysis Cells - Influence of Acetate and Propionate Concentration.

Microbial electrolysis cells (MECs) are widely considered as a next generation wastewater treatment system. However, fundamental insight on the temporal dynamics of microbial communities associated with MEC performance under different organic types with varied loading concentrations is still unknown, nevertheless this knowledge is essential for optimizing this technology for real-scale applications. Here, the temporal dynamics of anodic microbial communities associated with MEC performance was examined at low (0.5 g COD/L) and high (4 g COD/L) concentrations of acetate or propionate, which are important intermediates of fermentation of municipal wastewaters and sludge. The results showed that acetate-fed reactors exhibited higher performance in terms of maximum current density (I: 4.25 ± 0.23 A/m2), coulombic efficiency (CE: 95 ± 8%), and substrate degradation rate (98.8 ± 1.2%) than propionate-fed reactors (I: 2.7 ± 0.28 A/m2; CE: 68 ± 9.5%; substrate degradation rate: 84 ± 13%) irrespective of the concentrations tested. Despite of the repeated sampling of the anodic biofilm over time, the high-concentration reactors demonstrated lower and stable performance in terms of current density (I: 1.1 ± 0.14 to 4.2 ± 0.21 A/m2), coulombic efficiency (CE: 44 ± 4.1 to 103 ± 7.2%) and substrate degradation rate (64.9 ± 6.3 to 99.7 ± 0.5%), while the low-concentration reactors produced higher and dynamic performance (I: 1.1 ± 0.12 to 4.6 ± 0.1 A/m2; CE: 52 ± 2.5 to 105 ± 2.7%; substrate degradation rate: 87.2 ± 0.2 to 99.9 ± 0.06%) with the different substrates tested. Correlating reactor’s performance with temporal dynamics of microbial communities showed that relatively similar anodic microbial community composition but with varying relative abundances was observed in all the reactors despite differences in the substrate and concentrations tested. Particularly, Geobacter was the predominant bacteria on the anode biofilm of all MECs over time suggesting its possible role in maintaining functional stability of MECs fed with low and high concentrations of acetate and propionate. Taken together, these results provide new insights on the microbial community dynamics and its correlation to performance in MECs fed with different concentrations of acetate and propionate, which are important volatile fatty acids in wastewater.