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1.
Sci Total Environ ; 710: 136303, 2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-31923673

RESUMO

Denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) are critical dissimilatory nitrate reduction pathways that determine nitrogen (N) removal and internal recycling in aquatic environments. However, the relative important of DNRA, and the influences of environmental factors on DNF and DNRA, have not been widely studied in freshwater lakes. In our study, we used N isotope-tracing to investigate the potential rates of DNF and DNRA in 27 lakes from the Eastern Plain Lake Zone (EPL), China. In the EPL lakes, DNF was the dominant nitrate reduction process, however DNRA was still important, accounting for around 4.3%-21.9% of total nitrate reduction. The sediment organic carbon was the primary factor controlling the rates of dissimilatory nitrate reduction, accounting for 28.3% and 37.9% of the variance in DNF and DNRA rates, respectively. High algal biomass accelerated DNF rates, while indirectly affected DNRA via changing the quality of organic carbon. The greater contributions of DNRA to dissimilatory nitrate reduction were found in lakes with higher sulfate concentrations. DNRA coupled to sulfur cycling may play an important role in lakes with high sulfate concentrations and high sediment organic carbon. This study highlights the important role played by DNRA in total nitrate reduction pathways of freshwater lakes. Mitigation strategies for N pollution and algal blooms should not only target decrease of nutrient input, strategies should also create a suitable environment for improving N removal and inhibit N recycling.

2.
Neurochem Res ; 45(4): 837-850, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31939088

RESUMO

Brain injury has been proposed as the major cause of the poor outcomes associated with intracerebral hemorrhage (ICH). Emerging evidence indicates that the nuclear receptor, peroxisome proliferator-activated receptor ß/δ (PPAR-ß/δ), plays a crucial role in the pathological process of central nervous impairment. The present study was undertaken to evaluate the protective effects of PPAR-ß/δ activation using a selective PPAR-ß/δ agonist, GW0742, against brain injury after ICH in a mouse model. ICH was induced by intravenous injection of collagenase into the right caudate putamen. To examine the protective effect of PPAR-ß/δ activation against ICH-induced brain injury, mice were either intraperitoneally injected with GW0742 (3 mg/kg, body weight) or saline (control group) 30 min before inducing ICH. Behavioral dysfunction was evaluated 24 and 72 h after injury. Then, all mice were killed to assess hematoma volume, brain water content, and blood-brain barrier (BBB) permeability. TUNEL and Nissl staining were performed to quantify the brain injury. The expression of PPAR-ß/δ, interleukin (IL)-1ß, tumor necrosis factor (TNF)-α, Bcl-2-related X-protein (Bax), and B-cell lymphoma 2 (Bcl-2) in the perihematomal area was examined by immunohistochemistry and western blotting analysis. Mice treated with GW0742 showed significantly less severe behavioral deficits compared to the control group, accompanied by increased expression of PPAR-ß/δ and Bcl-2, and increased expression of IL-1ß, TNF-α, and Bax decreased simultaneously in the GW0742-treated group. Furthermore, the GW0742-pretreated group showed significantly less brain edema and BBB leakage. Neuronal loss was attenuated, and the number of apoptotic neuronal cells in perihematomal tissues reduced, in the GW0742-pretreated group compared to the control group. However, the hematoma volume did not decrease significantly on day 3 after ICH. These results suggest that the activation of PPAR-ß/δ exerts a neuroprotective effect on ICH-induced brain injury, possibly through anti-inflammatory and anti-apoptotic pathways.

3.
Appl Environ Microbiol ; 86(6)2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-31924617

RESUMO

The revolution of molecular techniques has revealed that the composition of natural bacterial communities normally includes a few abundant taxa and many rare taxa. Unraveling the mechanisms underlying the spatial assembly process of both abundant and rare bacterial taxa has become a central goal in microbial ecology. Here, we used high-throughput sequencing to explore geographic patterns and the relative importance of ecological processes in the assembly of abundant and rare bacterial subcommunities from 25 lakes across the middle and lower reaches of Yangtze River basin (MLYB), located in Southeast China, where most of the lakes are interconnected by river networks. We found similar biogeographic patterns of abundant and rare subcommunities which could significantly distinguish the community compositions of the two lake groups that were far from each other but which could not distinguish the community compositions of the nearby lakes. Both abundant and rare bacteria followed a strong distance-decay relationship. These findings suggest that the interconnectivity between lakes homogenizes the bacterial communities in local areas, and the abundant and rare taxa therein may be affected by the same ecological process. In addition, based on the measured environmental variables, the deterministic processes explain a small fraction of variation within both abundant and rare subcommunities, while both neutral and null models revealed a high stochasticity ratio for the spatial distribution patterns of both abundant and rare taxa. These findings indicate that the stochastic processes exhibited a greater influence on both abundant and rare bacterial subcommunity assemblies among interconnected lakes.IMPORTANCE The middle and lower Yangtze Plain is a typical floodplain in which many lakes connect with each other, especially in the wet season. More importantly, with the frequent change of regional water level in the wet season, there is a mutual hydrodynamic exchange among these lakes. The microbial biogeography among these interconnected lakes is still poorly understood. This study aims to unravel the mechanisms underlying the assembly process of abundant and rare bacteria among the interconnected lakes in the middle and lower Yangtze Plain. Our findings will provide a deeper understanding of the biogeographic patterns of rare and abundant bacterial taxa and their determined processes among interconnected aquatic habitats.

4.
Environ Int ; 134: 105330, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31759274

RESUMO

Dissolved organic matter (DOM) released from permafrost thaw greatly influences the biogeochemical cycles of, among others, downstream carbon, nitrogen and phosphorus cycles; yet, knowledge of the linkages between bacterial communities with permafrost DOM heterogeneity is limited. Here, we aim at unravelling the responses of bacterial diversities and metabolic profiles to DOM quantity and composition across permafrost thawing gradients by coupling an extensive field investigation with bio-incubation experiments. Richness, evenness and dissimilarities of the whole and rare communities decreased from thermokarst pits to headstreams and to downstream rivers. The assemblages of the abundant subcommunities were mainly determined by ecological drift-driven stochastic processes. Both the optical and the molecular composition of DOM were significantly related to the changes of the whole (rare) bacterial communities (Mantel's correlation > 0.5, p < 0.01). Diversity indices of the whole and rare communities decreased with decreasing relative abundance of tannins, condensed aromatics and more aromatic and oxidized lignins as well as with decreased dissolved organic carbon and intensities of all fluorescence components. Laboratory DOM bio-incubation experiments further confirmed microbial consumption of more aromatic and oxidized compounds as well as decreasing metabolic diversities in terms of microbial degradation and production along permafrost thawing gradients. Our findings suggest that changes in the sources of permafrost-derived DOM induced by global warming can have different influences on the diversity and metabolism of bacterial communities and thus on permafrost carbon climate feedbacks along permafrost thawing gradients.

5.
Huan Jing Ke Xue ; 41(1): 183-193, 2020 Jan 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854919

RESUMO

In order to improve water quality, many urban lakes in China have undergone environmental restoration since the introduction of China's tenth five-year plan. To understand the effectiveness of improvement projects on eutrophic urban lakes, we analyze the changes in water quality of Lihu Lake over the past 30 years, i.e., before and after comprehensive remediation. We use long-term monitoring data from TLLER and from two regional investigations undertaken in 2017. The results were as follows. ① Concentrations of total nitrogen (TN) and total phosphorus (TP), the permanganate index, and chlorophyll-a (Chl-a) in Lihu Lake all increased dramatically since the 1990s and reached the worst levels during the period from 1997 to 2003. After comprehensive improvement measures for the lake undertaken by the local government in 2003, the water quality improved remarkably year by year, but reduced slightly in the past two years assessed here. There was no obvious improvement in water transparency when comparing data from before to after the remediation. ② Before the improvement measures, the water quality fluctuated greatly with season, however, water quality sampled during the winter post remediation was significantly better than during the summer. ③ Spatially, the water quality in the western region of Lihu Lake was significantly better than of that in the eastern region. When comparing government measures in different eutrophic urban lakes, we found that engineering management measures can improve the water quality of urban lakes over a relatively short time period. However, after the water quality has been improved, it is necessary to restore the macrophyte-dominated ecosystem, which should be supplemented by ecological restoration based on biological regulation. By improving species diversity, the aquatic ecosystem can be successfully transformed from being phytoplankton-dominated to macrophyte-dominated, thereby enabling the service functions of a lake ecosystem to be truly restored.

6.
Artigo em Inglês | MEDLINE | ID: mdl-31816827

RESUMO

Bacterial pathogens are one of the causes of human diseases and have a serious impact on environmental health. In this study, we investigated the bacterial pathogen community in 88 sites at rivers around Lake Chaohu Basin, China, using Illumina miseq sequencing. The results showed that three opportunistic pathogens: Acinetobacter, Massilia, and Brevundimonas, were the three abundant bacterial genera in all samples, and had a relative abundance of 0.33 to 49.28% (average 8.80%), 0.06 to 25.4% (average 4.6%), 0.01 to 12.82% (average 2.6%) of all bacterial sequences, respectively. Our results indicated that a high abundance of opportunistic pathogens was observed in the rivers of the Lake Chaohu Basin, and that effective treatment and monitoring of sewage entering into rivers should be further strengthened.

7.
Water Res ; 160: 18-28, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31129378

RESUMO

Dissolved organic matter (DOM) from alpine glaciers is highly biolabile and plays a vital role in the biogeochemical cycle of meltwater-impacted environments. To unravel the composition and interactions of DOM with the bacterial community in glacier and glacier meltwater, we conducted sampling of two different Tibetan Plateau glaciers and carried out laboratory bio-incubation experiments. The field data revealed that four protein-like components accounted for 86.0 ±â€¯11.9% of the total variability of all six fluorescence components, which suggests a predominantly microbial source of glacial chromophoric DOM (CDOM). The ice and meltwater samples displayed major contributions of molecular formulae associated with lipids and proteins (i.e. high H/C) as revealed by ultrahigh resolution mass spectrometry. Multiple linear regression models revealed that the abundant phyla explain 64.2%, 61.3%, and 65.0% of the variability of microbial and terrestrial humic-like, and protein-like components, respectively. Correlation-based network analysis determined the metabolic niches of the bacterial community members associated with different fluorescence types in biogeochemical processes. Furthermore, laboratory DOM bio-incubation experiments confirmed that sub-components of the CDOM pool differentially participate in bacterial metabolism. We therefore conclude that the bacterial community interacted closely with the compositional variability of DOM in the investigated alpine glacial environments by both producing and consuming of DOM.


Assuntos
Ecossistema , Camada de Gelo , Bactérias , Espectrometria de Fluorescência , Tibet
8.
Lipids Health Dis ; 18(1): 104, 2019 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-31010436

RESUMO

BACKGROUND: In recent years, an increasing number of studies have proved that circulating miRNAs could be used for the early diagnosis of cardiovascular diseases and even play vital roles in the evaluation of therapeutic effects or prognosis. This study was conducted to examine the correlation between serum microRNAs and hyperlipidemia to provide a theoretical basis for the early screening and intervention of atherosclerotic cardiovascular diseases (ASCVD). METHODS: The serum samples and clinical data of 122 patients with hyperlipidemia and 168 healthy subjects were collected. Related clinical information was statistically analyzed for the two groups. Expression of circulating miRNAs was detected by miRNA microarray analysis and further verified by reverse transcription-quantitative PCR (RT-qPCR). RESULTS: Statistical analysis of clinical information revealed a significant difference in the incidence of ASCVD between the two groups. The MiRNA microarray analysis (n = 10) showed 22 miRNAs with significantly different expression, among which 12 showed upregulation, and the others showed downregulation. Those possessing obvious differences and stable expression in the miRNA microarray, including miRNA-191-3p, miRNA-933, and miRNA-425-3p, were chosen for further investigation using RT-qPCR. The results demonstrated that several miRNAs were related to lipid metabolism disorders, especially miRNA-933. The area under the curve (AUC) of miRNA-933 in distinguishing the hyperlipidemia and ASCVD patients was 0.739 (95% CI, 0.682-0.795; P < 0.01) and 0.703 (95% CI, 0.643-0.763, P < 0.01), respectively. CONCLUSIONS: In conclusion, miRNA-191-3p, miRNA-933, and miRNA-425-3p may be depressed in the peripheral circulation of patients with lipid metabolism disorders (mainly LDL). Circulating miRNA-933 could be a feasible predictor for ASCVD at the early stage.


Assuntos
Aterosclerose/sangue , Aterosclerose/genética , MicroRNA Circulante/genética , Hiperlipidemias/sangue , Hiperlipidemias/genética , Área Sob a Curva , Estudos de Casos e Controles , MicroRNA Circulante/metabolismo , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Humanos , Masculino , Pessoa de Meia-Idade
9.
BMC Microbiol ; 18(1): 195, 2018 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-30470189

RESUMO

BACKGROUND: Understanding the recovery of bacterial communities after extreme environmental disturbances offers key opportunities to investigate ecosystem resilience. However, it is not yet clear whether bacterial communities can rebound to their pre-disturbance levels. To shed light on this issue, we tracked the responses of bacterial communities during an extreme salinization-desalinization cycle. RESULTS: Our results showed that salinization-up process induced an ecological succession, shifting from a community dominated by Betaproteobacteria to Gammaproteobacteria. Within the desalinization-down process, taxon-specific recovery trajectories varied profoundly, with only Gammaproteobacteria returning to their initial levels, of which Alphaproteobacteria was the most prominent member. The α-diversity indices gradually increased at oligosaline environment (0.03‰ to 3‰) and subsequently decreased profoundly at hypersaline condition (10‰ to 90‰). However, the indices did not return to pre-disturbance level along the previous trajectory observed during the desalinization. Approximately half of the original OTUs were not detected during desalinization, suggesting that the seed bank may be damaged by the hypersaline environment. Moreover, Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) implied that the osmosensors' capacity of bacterial communities was also impaired by the hypersaline condition. CONCLUSIONS: These results suggested that the bacterial communities showed a low recovery after the extreme salinization-desalinization cycle.


Assuntos
Bactérias/isolamento & purificação , Água Doce/química , Cloreto de Sódio/análise , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , DNA Bacteriano/genética , Ecossistema , Água Doce/microbiologia , Filogenia , RNA Ribossômico 16S/genética , Salinidade , Cloreto de Sódio/metabolismo
10.
Environ Sci Technol ; 52(19): 11049-11059, 2018 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-30168717

RESUMO

Harmful cyanobacterial blooms represent an increasing threat to freshwater resources globally. Despite increased research, the physiological basis of how the dominant bloom-forming cyanobacteria, Microcystis spp., proliferate and then maintain high population densities through changing environmental conditions is poorly understood. In this study, we examined the transcriptional profiles of the microbial community in Lake Taihu, China at 9 stations sampled monthly from June to October in 2014. To target Microcystis populations, we collected metatranscriptomic data and mapped reads to the M. aeruginosa NIES 843 genome. Our results revealed significant temporal gene expression patterns, with many genes separating into either early or late bloom clusters. About one-third of genes observed from M. aeruginosa were differentially expressed between these two clusters. Conductivity and nutrient availability appeared to be the environmental factors most strongly associated with these temporal gene expression shifts. Compared with the early bloom season (June and July), genes involved in N and P transport, energy metabolism, translation, and amino acid biosynthesis were down-regulated during the later season (August to October). In parallel, genes involved in regulatory functions as well as transposases and the production of microcystin and extracellular polysaccharides were up-regulated in the later season. Our observation indicates an eco-physiological shift occurs within the Microcystis spp. transcriptome as cells move from the rapid growth of early summer to bloom maintenance in late summer and autumn.


Assuntos
Cianobactérias , Microcystis , China , Lagos , Estações do Ano
11.
Environ Sci Pollut Res Int ; 25(31): 31543-31557, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30206827

RESUMO

While the important roles of microbial communities in oceanic hypoxic zones were beginning to be understood, little is known about microbial community associated with this phenomenon in shallow lakes. To address this deficit, both the bacterial and microbial eukaryotic communities of an ephemeral hypoxic area of Taihu Lake were characterized. The hypoxia provided nutritional niches for various bacteria, which results in high abundance and diversity. Specific bacterial groups, such as vadinBC27 subgroup of Bacteroidetes, Burkholderiales, Rhodocyclales, Pseudomonas, and Parcubacteria, were dominated in hypoxic sites and relevant to the fermentation, denitrification, nitrification, and sulfur metabolism. Conversely, most of microbial eukaryotes disappeared along with the decline of DO. An unexpected dominance of fungi was observed during hypoxia, which partly explained by the accumulation of toxic algae. Mucor was the single dominant genus in the hypoxic zone. We proposed that this group might cooperate with bacterial communities in the anaerobic degradation of algal biomass and woody materials. Generally, the hypoxic microbiome in shallow lakes is mainly involved in fermentative metabolism depending on phytodetritus and is potentially influenced by terrestrial sources. This study provided new insights into the unique microbiome in short-term hypoxia in shallow lakes and lays the foundation for studies that will enhance our understanding of the microbial players associated with hypoxia and their adaption strategy on the global scale.


Assuntos
Monitoramento Ambiental , Eutrofização , Lagos/microbiologia , Bactérias/metabolismo , Bacteroidetes , Betaproteobacteria , China , Desnitrificação , Eucariotos , Lagos/parasitologia , Microbiota , Nitrificação , Filogenia
12.
Environ Sci Pollut Res Int ; 25(26): 26550-26561, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29992414

RESUMO

Artificial carriers are widely used to enhance the formation of biofilm and improve pollutants' removal efficiency in agricultural wastewater treatment ditches (eco-ditches), yet comprehensive insight into their bacterial community is scarce. In this study, bacterial diversities in four different habitats-the water column, surface sediments, submerged macrophytes (Myriophyllum verticillatum L.), and the artificial carriers (bio-cord)-were compared in a Chinese eco-ditch. Comparable richness and evenness of bacterial communities were observed on M. verticillatum and bio-cord, both being higher than for free-living bacteria in the water column but lower than for bacteria in the surface sediment. The highest similarity of bacterial community composition and structure also occurred between M. verticillatum and the bio-cord, dominated by α- and γ-proteobacteria, Verrucomicrobia, and Bacteroidetes. Firmicutes and Planctomycetes, respectively, were the exclusive abundant phyla in M. verticillatum and the bio-cord, probably indicating the unique interaction between M. verticillatum and their epiphytic bacteria. Some abundant genera, such as Roseomonas, Pseudomonas, and Rhodopirellula, which were exclusively observed in M. verticillatum or the bio-cord, have been reported to have the same capacity to remove nitrogen and organic matter in wastewater treatment systems. In conclusion, in the studied eco-ditch, the bio-cord was found to play a similar role as submerged macrophytes in harboring bacterial assemblages, and we therefore propose that bio-cord may be a good alternative or supplement to enhance wastewater treatment in agricultural ditches.


Assuntos
Bactérias/crescimento & desenvolvimento , Biofilmes/crescimento & desenvolvimento , Saxifragales/crescimento & desenvolvimento , Águas Residuárias , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Agricultura , Bactérias/classificação , China , Ecossistema , Microbiota , Nitrogênio/análise , Saxifragales/microbiologia , Águas Residuárias/química , Águas Residuárias/microbiologia
13.
Sci Total Environ ; 639: 876-887, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-29929326

RESUMO

Fluvial plain lake watersheds are usually highly urbanized and have high concentrations of chromophoric dissolved organic matter (CDOM). CDOM derived from the connecting urban channels usually share strong terrestrial and anthropogenic signals and net inflow runoff (Qnet) to the lake serves as a proxy of residential household sewage input. We investigate how Qnet controls the optical characteristics of CDOM in fluvial plain Lake Taihu and the connecting channels. CDOM absorption coefficient a(350), dissolved organic carbon (DOC), the fluorescence intensity (Fmax) of seven PARAFAC components C1-C7, and δ15N-TDN were higher in the northwestern relative to the other lake regions, and a(250)/a(365), spectral slope S275-295, and δ13C-DOM relative low in the northwestern lake, all indicating strong terrestrial and anthropogenic effects. Conversely, the urban land cover (%Cities), gross domestic product (GDP), and population density were relatively low in the western sub-watersheds and high in the eastern sub-watersheds. This apparent paradox reflects variations in Qnet from different sub-watersheds. Thus, significant positive relationships were found between Qnet and a(350), DOC, chemical oxygen demand (COD), chlorophyll-a (Chl-a), Fmax of C1-C3 and C6-C7, and %C2-%C3 in the five hydraulic sub-watersheds. We revealed significant positive relationships between mean a(350), DOC, COD, Chl-a, C1-C3 and C6, %C2-%C3, and the products of Qnet × %Cities, Qnet × GDP, and Qnet × population density. We further found dominant contribution of lignin to the total number of assigned formulas for the samples collected from the channels in the Huxi watershed and the central lake using high resolution mass spectroscopy. We conclude that Qnet is of key importance for the optical properties of CDOM molecules in the various regions of Lake Taihu and the connecting channels.

14.
PLoS One ; 13(5): e0195205, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29723219

RESUMO

Cyanobacterial blooms are a worldwide environmental problem and frequently occur in eutrophic lakes. Organophosphorus mineralization regulated by microbial alkaline phosphatase provides available nutrients for bloom regeneration. To uncover the dynamics of bacterial alkaline phosphatase activity and microbial backgrounds in relation to organophosphorus mineralization during the decomposition process of cyanobacterial blooms, the response of alkaline phosphatase PhoX-producing bacteria were explored using a 23-day mesocosm experiment with three varying densities of Microcystis biomass from eutrophic Lake Taihu. Our study found large amounts of soluble reactive phosphorus and dissolved organophosphorus were released into the lake water during the decomposition process. Bacterial alkaline phosphatase activity showed the peak values during days 5~7 in groups with different chlorophyll-a densities, and then all decreased dramatically to their initial experimental levels during the last stage of decomposition. Bacterial phoX abundances in the three experimental groups increased significantly along with the decomposition process, positively related to the dissolved organic carbon and organophosphorus released by the Microcystis blooms. The genotypes similar to the phoX genes of Alphaproteobacteria were dominant in all groups, whereas the genotypes most similar to the phoX genes of Betaproteobacteria and Cyanobacteria were also abundant in the low density (~15 µg L-1 chlorophyll-a) group. At the end of the decomposition process, the number of genotypes most similar to the phoX of Betaproteobacteria and Cyanobacteria increased in the medium (~150 µg L-1 chlorophyll-a) and high (~1500 µg L-1 chlorophyll-a) density groups. The released organophosphorus and increased bacterial phoX abundance after decomposition of Microcystis aggregates could potentially provide sufficient nutrients and biological conditions for algal proliferation and are probably related to the regeneration of Microcystis blooms in eutrophic lakes.


Assuntos
Ambiente Controlado , Eutrofização , Genes Bacterianos/genética , Microcystis/genética , Microcystis/metabolismo , Fósforo/metabolismo , Sequência de Bases , Fenômenos Químicos , Variação Genética , Genótipo , Lagos/microbiologia , Minerais/metabolismo , Filogenia
15.
Microbes Environ ; 33(2): 127-134, 2018 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-29794413

RESUMO

Rivers and their tributaries sculpt the earth's surface, and play an important role in substance circulation and energy flow. Bacteria are involved in most biogeochemical processes in the fluvial ecosystem; however, their pattern distribution in a river and its tributaries has not yet been investigated in detail. In the present study, high-throughput sequencing was employed to examine bacterial communities and their co-occurrence networks between Kaidu River and its nine tributaries in northwestern China. The results obtained demonstrated that both bacterial communities shared a similar dominant sub-community, mainly consisting of Actinobacteria, Bacteroidetes, and Proteobacteria, with Limnohabitans and Variovorax as the dominant genera. In spite of these commonalities, bacterial community structures still significantly differed between these two habitats, which may be related to the distance-related dispersal limitation. Their co-occurrence networks were generally both positively structured. The structural analysis showed that OTUs from the same phyla were more likely to co-occur. Although the keystone genera were taxonomically different between Kaidu River and its tributaries, they both shared common trophic properties in exploiting niches under oligotrophic conditions. We noted that their relative abundances were less than 1%, indicating the over-proportional roles of rare genera in the bacterial community. In addition, the inferred networks showed less nodes and edges, but higher modularity in Kaidu River than its tributaries, suggesting the higher fragmentation of the bacterial community in the mainstream.


Assuntos
Bactérias/classificação , Biodiversidade , Interações Microbianas , Rios/microbiologia , Microbiologia da Água , Bactérias/genética , China , Biologia Computacional , DNA Bacteriano , Ecossistema , Metagenômica , RNA Ribossômico 16S/genética
16.
Microbiologyopen ; 7(6): e00608, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-29573241

RESUMO

Worldwide cyanobacterial blooms greatly impair ecosystems in many eutrophic lakes and impact the microbial environment. In particular, large cyanobacterial colonies that are buoyant on the water surface may provide a distinct habitat for bacteria from other small particles that are suspended stably in the water column. To test this hypothesis, bacterial communities (excluding cyanobacteria) attached to large particles dominated by cyanobacterial colonies (>120 µm, LA), small particles (3-36 µm, SA), and free-living bacteria (0.2-3 µm, FL) were investigated monthly for a year in Lake Taihu, China. Results confirmed that the Shannon diversity index of LA was significantly lower than that of FL, which was lower than that of SA. Cytophagia and Alphaproteobacteria were specially enriched in LA. Although samples in each habitat collected during high- (May to November) and low-bloom seasons (December to April) were separated, all samples in LA were clustered and separated from SA and FL, which were also clustered during the same sampling seasons. In addition, the bacterial communities in LA were correlated with nitrate level, whereas FL and SA were correlated with nitrate level and temperature. Mantel analysis revealed that bacterial composition significantly correlated with the cyanobacterial composition in LA and FL but not in SA. These results indicate that LA provides distinct niches to bacteria, whereas the differentiation of bacterial communities in FL and SA is seasonally dependent.


Assuntos
Cianobactérias/crescimento & desenvolvimento , Cianobactérias/isolamento & purificação , Lagos/microbiologia , Biodiversidade , China , Cianobactérias/classificação , Cianobactérias/genética , Lagos/química , Filogenia , Estações do Ano
17.
J Microbiol ; 56(2): 104-112, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29392556

RESUMO

The patterns of macrobiota in lotic ecosystems have been extensively explored, however, the dynamics of microbiota remain poorly investigated, especially in the high-elevation region. To address this deficit, we collected eight samples to unveil the bacterial and archaeal community in the Kaidu river, located at the arid region of northwestern China (an average of 2,500 m a.s.l.). For the bacterial community, phylogenetically Betaproteobacteria prevailed, followed by Alphaproteobacteria and Actinobacteria; at the finer genus level, Limnohabitans and Variovorax were prominent. Along the river, the bacterial community showed a continuous succession. Specifically, their α- and ß-diversity gradually increased, suggesting a distance-decay pattern. Additionally, there was an ecological transition between the dominant and the rare sub-community along the river: the relative abundance of the dominant members gradually decreased as the rare members increased. We report that temperature and spatial distance were significantly related to the variation of bacterial community. Variance partitioning analysis showed that the environmental factors contributed more to the bacterial community than did the spatial distance. In the case of the archaeal community, the methanogenic groups, mainly Methanosaeta and Methanosarcina, were prominent within the Kaidu river. Unlike the continuous change in the patterns of the bacterial community, the archaeal community showed a constant pattern along the river. Our results showed that the archaeal community was independent of the environmental and spatial factors. We propose that the inoculation of soil-derived archaea is responsible for the archaeal community in the Kaidu river. Together, our study demonstrated that the bacterial community in the high-elevation Kaidu river is a continuum, whereas the archaeal community is not.


Assuntos
Archaea/classificação , Bactérias/classificação , Consórcios Microbianos , Filogenia , Rios/microbiologia , Microbiologia da Água , Archaea/genética , Bactérias/genética , Biodiversidade , China , DNA Arqueal/genética , DNA Bacteriano/genética , Ecossistema , Meio Ambiente , RNA Ribossômico 16S/genética , Temperatura Ambiente
18.
Harmful Algae ; 68: 168-177, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28962977

RESUMO

Cyanobacterial harmful algal blooms are prevalent around the world, influencing aquatic organisms and altering the physico-chemical properties in freshwater systems. However, the response of bacterial communities to toxic cyanobacterial blooms and associated microcystins (MC) remain poorly understood even though global concentrations of MC have increased dramatically in the past few decades. To address this issue, the dynamics of bacterial community composition (BCC) in the water column and how BCC is influenced by both harmful cyanobacterial blooms and environmental factors were investigated on a monthly basis from August 2013 to July 2014 in Lake Taihu, China. Non-metric multidimensional scaling (NMDS) revealed that seasonal variation in BCC was significant, and that the succession of BCC greatly depends on changes in environmental conditions. Redundancy analysis (RDA) results showed that the overall variation of BCC was explained mainly by dissolved oxygen (DO), nitrate nitrogen (NO3--N), and Microcystis. The alpha biodiversity of the bacterial community was different among months with the highest diversity in February and the lowest diversity in October. Furthermore, significant negative relationships were found between alpha biodiversity indices and Microcystis abundance as well as with intracellular MC concentrations, indicating that Microcystis and associated MC may influence the bacterial community structure by reducing its biodiversity. This study shows that potential associations exist between toxic cyanobacterial blooms and bacterial communities but more investigations are needed to obtain a mechanistic understanding of their complex relationships.


Assuntos
Cianobactérias/fisiologia , Proliferação Nociva de Algas/fisiologia , Lagos/microbiologia , Microbiota , Biodiversidade , China , Clorofila A/análise , Microcistinas/análise , Estações do Ano , Fatores de Tempo
19.
Chemosphere ; 188: 608-617, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28917213

RESUMO

Lake Bosten is the largest oligosaline lake in arid northwestern China, and water from its tributaries and evaporation control the water balance of the lake. In this study, water quality and chromophoric dissolved organic matter (CDOM) absorption and fluorescence were investigated in different seasons to elucidate how hydraulic connectivity and evaporation may affect the water quality and variability of CDOM in the lake. Mean suspended solids and turbidity were significantly higher in the upstream tributaries than in the lake, the difference being notably more pronounced in the wet than in the dry season. A markedly higher mean first principal component (PC1) score, which was significantly positively related to protein-like components, and a considerably lower fluorescence peak integration ratio - IC:IT, indicative of the terrestrial humic-like CDOM contribution percentage, were observed in the lake than in the upstream tributaries. Correspondingly, notably higher contribution percentages of terrestrial humic-like components were observed in the river mouth areas than in the remaining lake regions. Furthermore, significantly higher mean turbidity, and notably lower mean conductivity and salinity, were recorded in the southwestern Kaidu river mouth than in the remaining lake regions in the wet season. Notably higher mean salinity is recorded in Lake Bosten than in upstream tributaries. Autochthonous protein-like associated amino-acids and also PC1 scores increased significantly with increasing salinity. We conclude that the dynamics of water quality and CDOM composition in remote arid Lake Bosten are strongly driven by evaporation and also the hydraulic connectivity between the upstream tributaries and the downstream lake.


Assuntos
Monitoramento Ambiental/métodos , Lagos , Qualidade da Água , China , Fluorescência , Substâncias Húmicas/análise , Nefelometria e Turbidimetria , Rios , Salinidade , Estações do Ano
20.
PLoS One ; 12(9): e0184146, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28873456

RESUMO

Microcystis aeruginosa is a freshwater bloom-forming cyanobacterium capable of producing the potent hepatotoxin, microcystin. Despite increased interest in this organism, little is known about the viruses that infect it and drive nutrient mobilization and transfer of genetic material between organisms. The genomic complement of sequenced phage suggests these viruses are capable of integrating into the host genome, though this activity has not been observed in the laboratory. While analyzing RNA-sequence data obtained from Microcystis blooms in Lake Tai (Taihu, China), we observed that a series of lysogeny-associated genes were highly expressed when genes involved in lytic infection were down-regulated. This pattern was consistent, though not always statistically significant, across multiple spatial and temporally distinct samples. For example, samples from Lake Tai (2014) showed a predominance of lytic virus activity from late July through October, while genes associated with lysogeny were strongly expressed in the early months (June-July) and toward the end of bloom season (October). Analyses of whole phage genome expression shows that transcription patterns are shared across sampling locations and that genes consistently clustered by co-expression into lytic and lysogenic groups. Expression of lytic-cycle associated genes was positively correlated to total dissolved nitrogen, ammonium concentration, and salinity. Lysogeny-associated gene expression was positively correlated with pH and total dissolved phosphorous. Our results suggest that lysogeny may be prevalent in Microcystis blooms and support the hypothesis that environmental conditions drive switching between temperate and lytic life cycles during bloom proliferation.


Assuntos
Bacteriófagos/genética , Eutrofização , Lisogenia/genética , Microcystis/virologia , Transcriptoma/genética , Meio Ambiente , Perfilação da Expressão Gênica , Regulação Viral da Expressão Gênica , Genoma Viral , Filogenia
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