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1.
Sci Total Environ ; 701: 134601, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31734485

RESUMO

Glyphosate-based herbicides are the most commonly used herbicide worldwide. Although glyphosate is known to be toxic to aquatic organisms, it can also have stimulatory effects on small-size (ø <2 µm) cyanobacteria (Pcy) able to metabolize and degrade glyphosate and AMPA. Several previous experimental studies in micro- and mesocosms reported increases of Pcy abundance in response to glyphosate additions, but comparable field evidence is presently unavailable. We surveyed a large geographical area in order to collect information on Pcy abundance from lakes within the Pampa region (with over three decades of glyphosate usage) and lakes from Patagonia (with virtually no history of glyphosate usage). Fifty-two Pampean lakes and 24 Patagonian lakes were surveyed. We used three indicators of glyphosate impact: herbicide concentration, the presence of phosphonate metabolism genes (responsible for glyphosate and AMPA degradation) in environmental DNA samples, and descriptors of land use in the surrounding area of each lake. We addressed three questions: (1) is there field evidence of stimulatory effects of glyphosate on picocyanobacteria abundance? (2) is the magnitude of the effects of glyphosate in natural systems comparable to that reported under controlled experimental conditions? and (3), how do the effects of glyphosate compare to the effects of other potential environmental drivers of Pcy biomass? The collected evidence is consistent with the hypothesis that long-term agricultural practices relying on glyphosate-based technologies had important effects on freshwater microbial communities, particularly by promoting increases in picocyanobacteria abundance.


Assuntos
Cianobactérias/fisiologia , Monitoramento Ambiental , Glicina/análogos & derivados , Herbicidas , Lagos/microbiologia , Agricultura , Poluentes Químicos da Água
2.
Huan Jing Ke Xue ; 40(7): 3099-3107, 2019 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854707

RESUMO

In order to explore the composition of epiphytic algae and its related environmental factors, 12 sampling sites in the natural reaches and the backwater reaches (including perennial backwater sections and fluctuating backwater sections) were investigated among tributaries of the Caotang River, the Meixi River, and the Daxi River in the Fengjie district of the Chongqing section of the Three Gorges Reservoir under different hydrological regimes (i.e., storage and non-storage periods). Results showed that 103 species of epilithic algae belonging to 45 genera and 4 families are found in the 3 tributaries. This included 67 species belonging to 34 genus in the natural sections and 82 species (64 species in perennial backwater sections and 41 species in fluctuating backwater sections) belonging to 34 genera in the backwater sections. During the storage period, the dominant species in the natural sections were Melosira varians, Cocconeis placentula, Diatoma vulgure, Gyrosigma scalproides, and Oscillatoria tenuis, while the dominant species in the backwater sections were M. varians, Cymbella affinis,D. vulgure, Eucapsis alpina, and M. granulata. During the non-storage period, the dominant species in the natural sections were M. varians, C. affinis, and C. placentula, whereas the dominant species in the backwater sections were O. princeps, O. rupicola,O. formosa, Synedra acus, Ulothrix sp., Merismopedia elegans, and O. tenuis. These results suggested that the compositions of dominant species showed significant differences during the non-storage period, while little difference was found during the storage period. In addition, the dominant species did not show a significant change in the natural sections, but a marked difference was observed in the backwater sections. Similar dominant species were observed in both perennial and fluctuating backwater sections during the non-storage period, but significantly different dominant species were found during the storage period. Redundancy analysis suggested that the composition of epilithic algae was influenced by different environmental factors, such as temperature, electrical conductivity, pH, total nitrogen, and total phosphorus. Indeed, changes in the cell densities of dominant algae at the different sites were mainly affected by temperature and the concentrations of nitrogen and phosphorus. These results suggest that the different hydrological regimes had an important role not only on the reservoir water environment, but also the dynamics of epilithic algal communities.


Assuntos
Cianobactérias/fisiologia , Monitoramento Ambiental , Rios , China , Nitrogênio/análise , Fósforo/análise , Estações do Ano
3.
Mar Pollut Bull ; 146: 355-365, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31426168

RESUMO

Human-induced eutrophication of coastal water may be a major threat to aquatic life. Here, we investigated the effects of N-rich well amelioration brines (WAB) on coastal phytoplankton population's habitat in the surface oligotrophic waters of the southeastern Mediterranean Sea (SEM). To this end, we added WAB (2 concentrations) to mesocosms (1-m3 bags) to surface SEM water during summer and winter, where changes in phytoplankton biomass, activity and diversity was monitored daily for 8 days. Our results demonstrate that WAB addition triggered a phytoplankton bloom, resulting in elevated algal biomass (maximal +780%), increased primary production rates (maximal +675%) and a decrease in eukaryotic algal α-diversity (ca. -20%). Among the species that bloomed following WAB amendments, we found the potentially toxic dinoflagellate Karlodinium venificum. This study adds valuable perspective to the effect of nutrients discharged into nutrient limited SEM coastal waters, and in particular of N-derived WAB.


Assuntos
Nitrogênio/metabolismo , Fitoplâncton/fisiologia , Água do Mar/química , Biodiversidade , Biomassa , Clorofila A/metabolismo , Cianobactérias/fisiologia , Ecossistema , Eucariotos/fisiologia , Eutrofização , Mar Mediterrâneo , Fitoplâncton/genética , RNA Ribossômico 18S , Estações do Ano
4.
Sci Total Environ ; 691: 1144-1154, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31466196

RESUMO

Rising atmospheric carbon dioxide (CO2) may stimulate the proliferation of cyanobacteria. To investigate the possible physiological responses of cyanobacteria to elevated CO2 at different nutrient levels, Microcystis aeruginosa were exposed to different concentrations of CO2 (400, 1100, and 2200 ppm) under two nutrient regimes (i.e., in nutrient-rich and nutrient-poor media). The results indicated that M. aeruginosa differed in its responses to elevated atmospheric CO2 at different nutrient levels. The light utilization efficiency and photoprotection of photosystem II were improved by elevated CO2, particularly when cells were supplied with abundant nutrients. In nutrient-poor media, both total organic carbon and the polysaccharide/protein ratio of the extracellular polymeric substance increased with elevated CO2, accompanied by high cellular carbon/nitrogen ratios. Besides, cells growing with fewer nutrients were more prone to suffer intracellular acidification with elevated CO2 than those growing with abundant nutrients. Nonetheless, alkaline phosphate activity of cyanobacteria was improved by high CO2, provided that reduced pH was in the optimum range for alkaline phosphate activity. Nitrate reductase activity was inhibited by elevated CO2 regardless of nutrient levels, leading to a reduced nitrate uptake. These changes indicate that the biogeochemical cycling of nutrients would be affected by higher atmospheric CO2 conditions. Overall, cyanobacteria in eutrophic waters may benefit more than in oligotrophic waters from rising atmospheric CO2 concentrations, and evaluations of the influence of rising atmospheric CO2 on algae should account for the nutrient level of the ecosystem.


Assuntos
Atmosfera/química , Dióxido de Carbono/análise , Cianobactérias/fisiologia , Eutrofização
5.
Sci Total Environ ; 695: 133804, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31419690

RESUMO

Once released into the environment antibiotics can kill or inhibit the growth of bacteria, and in turn potentially have effects on bacterial community structure and ecosystem function. Environmental risk assessment (ERA) seeks to establish protection limits to minimise chemical impacts on the environment, but recent evidence suggests that the current regulatory approaches for ERA for antibiotics may not be adequate for protecting bacteria that have fundamental roles in ecosystem function. In this study we assess the differences in interspecies sensitivity of eight species of cyanobacteria to seven antibiotics (cefazolin, cefotaxime, ampicillin, sufamethazine, sulfadiazine, azithromycin and erythromycin) with three different modes of action. We found that variability in the sensitivity to these antibiotics between species was dependent on the mode of action and varied by up to 70 times for ß-lactams. Probabilistic analysis using species sensitivity distributions suggest that the current predicted no effect concentration PNEC for the antibiotics may be either over or under protective of cyanobacteria dependent on the species on which it is based and the mode of action of the antibiotic; the PNECs derived for the macrolide antibiotics were over protective but PNECs for ß-lactams were generally under protective. For some geographical locations we identify a significant risk to cyanobacteria populations based upon measured environmental concentrations of selected antibiotics. We conclude that protection limits, as determined according to current regulatory guidance, may not always be protective and might be better derived using SSDs and that including toxicity data for a wider range of (cyano-) bacteria would improve confidence for the ERA of antibiotics.


Assuntos
Antibacterianos/toxicidade , Cianobactérias/fisiologia , Poluentes Químicos da Água/toxicidade , Antibacterianos/análise , Cianobactérias/efeitos dos fármacos , Monitoramento Ambiental , Medição de Risco , Poluentes Químicos da Água/análise
6.
Sci Total Environ ; 693: 133414, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31377351

RESUMO

Mixing regime and CO2 availability may control cyanobacterial blooms in polymictic lakes, but the underlying mechanisms still remain unclear. We integrated detailed results from a natural experiment comprising an average-wet year (2011) and one with heat waves (2012), a long-term meteorological dataset (1960-2010), historical phosphorus concentrations and sedimentary pigment records, to determine the mechanistic controls of cyanobacterial blooms in a eutrophic polymictic lake. Intense warming in 2012 was associated with: 1) increased stability of the water column with buoyancy frequencies exceeding 40 cph at the surface, 2) high phytoplankton biomass in spring (up to 125 mg WW L-1), 3) reduced downward transport of heat and 4) depleted epilimnetic CO2 concentrations. CO2 depletion was maintained by intense uptake by phytoplankton (influx up to 30 mmol m-2 d-1) in combination with reduced, internal and external, carbon inputs during dry, stratified periods. These synergistic effects triggered bloom of buoyant cyanobacteria (up to 300 mg WW L-1) in the hot year. Complementary evidence from polynomial regression modelling using historical data and pigment record revealed that warming explains 78% of the observed trends in cyanobacterial biomass, whereas historical phosphorus concentration only 10% thereof. Together the results from the natural experiment and the long-term record indicate that effects of hotter and drier climate are likely to increase water column stratification and decrease CO2 availability in eutrophic polymictic lakes. This combination will catalyze blooms of buoyant cyanobacteria.


Assuntos
Mudança Climática , Cianobactérias/fisiologia , Temperatura Alta/efeitos adversos , Lagos/análise , Fitoplâncton/fisiologia , Dióxido de Carbono/análise , Sedimentos Geológicos/química , Lagos/química , Lagos/microbiologia , Fósforo/análise , Quebeque , Estações do Ano
7.
Ecotoxicol Environ Saf ; 182: 109426, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31301595

RESUMO

Quagga (Dreissena rostriformis bugensis) and zebra (D. polymorpha) mussels are broadcast spawners that produce planktonic, free swimming veligers, a life history strategy dissimilar to native North American freshwater bivalves. Dreissenid veligers require highly nutritious food to grow and survive, and thus may be susceptible to increased mortality rates during harsh environmental conditions like cyanobacteria blooms. However, the impact of cyanobacteria and one of the toxins they can produce (microcystin) has not been evaluated in dreissenid veligers. Therefore, we exposed dreissenid veligers to eleven distinct cultures (isolates) of cyanobacteria representing Anabaena, Aphanizomenon, Dolichospermum, Microcystis, and Planktothrix species and the cyanotoxin microcystin to determine the lethality of cyanobacteria on dreissenid veligers. Six-day laboratory bioassays were performed in microplates using dreissenid veligers collected from the Detroit River, Michigan, USA. Veligers were exposed to increasing concentrations of cyanobacteria and microcystin using the green algae Chlorella minutissima as a control. Based on dose response curves formulated from a Probit model, the LC50 values for cyanobacteria used in this study range between 15.06 and 135.06 µg/L chlorophyll-a, with the LC50 for microcystin-LR at 13.03 µg/L. Because LC50 values were within ranges observed in natural waterbodies, it is possible that dreissenid recruitment may be suppressed when veliger abundances overlap with seasonal cyanobacteria blooms. Thus, the toxicity of cyanobacteria to dreissenid veligers may be useful to include in models forecasting dreissenid mussel abundance and spread.


Assuntos
Cianobactérias/fisiologia , Dreissena/fisiologia , Proliferação Nociva de Algas , Animais , Bivalves , Chlorella , Clorofila/análogos & derivados , Água Doce , Microcistinas , Microcystis , Plâncton , Rios
8.
Sci Total Environ ; 688: 867-879, 2019 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-31255824

RESUMO

Freshwater lakes are threatened by harmful blooms characterized by Cyanobacterial Aggregates (CAs) that are normally aggregated with extracellular polysaccharides released by cyanobacteria to form a phycosphere. It is possible that mutualistic relationships exist between bacteria and cyanobacteria in these CAs wherein bacterial products supplement cyanobacterial growth, and cyanobacterial exudates, in turn, serve as substrates for bacteria, thus augmenting the stability of each constituent. However, little is known about the exact interaction between cyanobacteria and their attached bacteria in CAs. Therefore, in this study, we collected 26 CA samples from Lake Taihu, a large freshwater lake in China from March of 2015 to February of 2016. We then sequenced both the V4 regions of 16S rRNA genes and full metagenomes, resulting in 610 Mb of 16S rRNA gene data and 198.98 Gb of high-quality metagenomic data. We observed that two cyanobacteria genera (Microcystis and Dolichospermum) alternately dominated CAs along the sampling time and specific bacterial genera attached to different cyanobacteria genera dominated CAs. More specifically, Dolichospermum dominates CAs when water temperature is low and total nitrogen is high, while Microcystis dominates CAs when water temperature is high and total nitrogen is low. Moreover, we found specific bacterial genera attached to different cyanobacteria genera dominated CAs. The cyanobacteria-bacteria related pairs Dolichospermum-Burkholderia and Microcystis-Hyphomonas were detected by ecological networks construction. Bacterial communities in CAs were found to be more correlated with the cyanobacterial community (Mantel's r = 0.76, P = 0.001) than with environmental factors (Mantel's r = 0.27, P = 0.017). A potential codependent nitrogen-cycling pathway between cyanobacteria and their attached bacteria was constructed, indicating their functional link. Overall, these results demonstrated that mutualistic relationships do, indeed, exist between cyanobacteria and bacteria in CAs at both taxonomic and gene levels, providing biological clues potentially leading to the control of blooms by interventional strategies to disrupt bacteria-cyanobacteria relationships and co-pathways.


Assuntos
Cianobactérias/fisiologia , China , Monitoramento Ambiental , Lagos , Nitrogênio , RNA Ribossômico 16S , Estações do Ano
9.
Life Sci Alliance ; 2(3)2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31160381

RESUMO

The cyanobacterial clock is controlled via the interplay among KaiA, KaiB, and KaiC, which generate a periodic oscillation of KaiC phosphorylation in the presence of ATP. KaiC forms a homohexamer harboring 12 ATP-binding sites and exerts ATPase activities associated with its autophosphorylation and dephosphorylation. The KaiC nucleotide state is a determining factor of the KaiB-KaiC interaction; however, its relationship with the KaiA-KaiC interaction has not yet been elucidated. With the attempt to address this, our native mass spectrometric analyses indicated that ATP hydrolysis in the KaiC hexamer promotes its interaction with KaiA. Furthermore, our nuclear magnetic resonance spectral data revealed that ATP hydrolysis is coupled with conformational changes in the flexible C-terminal segments of KaiC, which carry KaiA-binding sites. From these data, we conclude that ATP hydrolysis in KaiC is coupled with the exposure of its C-terminal KaiA-binding sites, resulting in its high affinity for KaiA. These findings provide mechanistic insights into the ATP-mediated circadian periodicity.


Assuntos
Trifosfato de Adenosina/metabolismo , Proteínas de Bactérias/metabolismo , Relógios Circadianos , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/metabolismo , Cianobactérias/fisiologia , Proteínas de Bactérias/química , Relógios Circadianos/genética , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/química , Hidrólise , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Conformação Molecular , Fosforilação , Ligação Proteica , Relação Estrutura-Atividade
10.
Mar Pollut Bull ; 142: 433-451, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31232322

RESUMO

Mesozooplankton was sampled seasonally in a large microtidal estuary (Peel-Harvey) suffering from massive macroalgal growths and cyanobacterial blooms. Comparisons with other estuaries indicate that eutrophication led to copepod abundance declining and macroalgal-associated species increasing. Mesozooplankton species are almost exclusively autochthonous, i.e. spend entire life cycle within the estuary. Meroplanktonic species are virtually absent because main benthic macroinvertebrate species undergo direct benthic rather than planktotrophic development. There are also few abundant holoplanktonic species. Most species are tychoplanktonic, i.e. benthic and transported into plankton through physical disturbance of sediment. Species number, concentration and Simpson's Index are greater during night than day. Annual cyclical changes in species composition are related closely to changes in salinity. At the most degraded site, nematode concentrations were high and the species number and concentration changed markedly during extreme eutrophication, when oxygen concentrations were low, disrupting annual cyclical changes in species composition.


Assuntos
Copépodes/fisiologia , Estuários , Eutrofização , Zooplâncton/fisiologia , Animais , Austrália , Cianobactérias/fisiologia , Monitoramento Ambiental , Densidade Demográfica , Salinidade , Estações do Ano
11.
Environ Sci Pollut Res Int ; 26(23): 24300-24304, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31250389

RESUMO

Soil surface-dwelling cyanobacteria constitute an important part of the dryland ecosystem. The exopolysaccharide (EPS) matrix they establish plays multiple roles in helping cells cope with harsh environments and also improves soil physicochemical properties. Anthropogenic atmospheric nitrogen or sulfur depositions have arisen as an important environmental change in drylands. The acid moisture derived from the depositions will be absorbed by cyanobacterial EPS matrix and thus may pose a threat to cells. In this communication, we evaluated this potential impact in a dryland cyanobacterium, Nostoc flagelliforme, which is a representative polysaccharide-rich species and shows remarkable resistance to desiccation stress. A strong and resilient pH buffering property was found for the EPS matrix, mainly of the polysaccharide's role, and this could protect the cells from acid damage of pH 4-6, a general acidity range of rainwater in the world. Unlike in acid aquatic environments, terrestrial xeric environments ensure N. flagelliforme unlikely to undertake lasting severe acidification. Thus, protection of the EPS matrix for dryland cyanobacteria would be conducive to sustain their growth and ecological roles in face of atmospheric acid pollution.


Assuntos
Chuva Ácida , Cianobactérias/fisiologia , Ecossistema , Polissacarídeos Bacterianos/metabolismo , Dessecação , Secas , Ecologia , Nitrogênio , Nostoc/fisiologia , Solo
12.
Mar Drugs ; 17(5)2019 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31083354

RESUMO

Siderophores are low-molecular-weight metal chelators that function in microbial iron uptake. As iron limits primary productivity in many environments, siderophores are of great ecological importance. Additionally, their metal binding properties have attracted interest for uses in medicine and bioremediation. Here, we review the current state of knowledge concerning the siderophores produced by cyanobacteria. We give an overview of all cyanobacterial species with known siderophore production, finding siderophores produced in all but the most basal clades, and in a wide variety of environments. We explore what is known about the structure, biosynthesis, and cycling of the cyanobacterial siderophores that have been characterized: Synechobactin, schizokinen and anachelin. We also highlight alternative siderophore functionality and technological potential, finding allelopathic effects on competing phytoplankton and likely roles in limiting heavy-metal toxicity. Methodological improvements in siderophore characterization and detection are briefly described. Since most known cyanobacterial siderophores have not been structurally characterized, the application of mass spectrometry techniques will likely reveal a breadth of variation within these important molecules.


Assuntos
Cianobactérias/fisiologia , Sideróforos/química , Sideróforos/fisiologia , Cianobactérias/metabolismo , Ácidos Hidroxâmicos/química , Ferro/metabolismo , Quelantes de Ferro/metabolismo , Compostos de Quinolínio/química , Compostos de Quinolínio/farmacologia , Sideróforos/biossíntese , Sideróforos/farmacologia
13.
Environ Sci Pollut Res Int ; 26(20): 20439-20453, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31102217

RESUMO

The seasonal succession of phytoplankton functional groups (PFGs), their ecological preferences, relationships between environmental variables and PFGs, and ecological status were investigated in the Batman Dam Reservoir, a warm monomictic reservoir, located in the Tigris River basin of Turkey. Altogether 60 species, 19 functional groups, and 10 prevailing functional groups were identified, and prevailing functional groups showed strong seasonal changes. Centric diatoms Cyclotella ocellata (group B) and Aulacoseira granulata (group P) were dominant in the spring, with water mixing and low temperature. Groups F (Elakatothrix gelatinosa, Elakatothrix gelatinosa, and Sphaerocystis schroeteri), J (Pediastrum simplex and Coelastrum reticulatum), G (Eudorina elegans and Volvox aureus), LM (Ceratium and Microcystis), and H1 (Aphanizomenon flos-aquae and Anabaena spiroides) dominated the phytoplankton community from summer to mid-autumn, with thermal stratification. Groups H1 and P became dominant in the late autumn, with the breakdown of stratification. With the deepening of the mixing zone, groups P and T (Mougeotia sp.) were dominant in the winter. The reservoir was meso-eutrophic according to trophic state index values based on total phosphorus (TP), chlorophyll a, Secchi depth and total nitrogen, habitat preferences of PFGs, and diversity indices of phytoplankton. Redundancy analysis (RDA) revealed that NO3-N, SiO2, TP, pH, and water temperature (WT) were the most important environmental factors controlling PFGs in the BDR. Weighted averaging regression results indicated that among PFGs, groups F and T had a narrower tolerance range for WT, pH, and SiO2, while groups G and T had a narrower tolerance range for TP and NO3-N.


Assuntos
Cianobactérias/fisiologia , Diatomáceas , Fitoplâncton/fisiologia , Clorofila A , Dinoflagelados/fisiologia , Ecossistema , Monitoramento Ambiental/métodos , Monitoramento Ambiental/estatística & dados numéricos , Água Doce/química , Concentração de Íons de Hidrogênio , Nitrogênio/análise , Fósforo/análise , Estações do Ano , Dióxido de Silício/análise , Temperatura Ambiente , Turquia
14.
Sci Total Environ ; 659: 1403-1414, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31096351

RESUMO

Many toxic and/or noxious cyanobacteria appear in nature with a filamentous, stacked cell arrangement called trichomes. Although water treatment can be optimized to keep cyanobacterial cells intact and avoid the release of toxic and/or noxious compounds, many physical and chemical stresses encountered during the treatment process may result in trichome truncation, decreasing treatment efficiency by allowing single cells or short trichomes to reach the product water. This makes it possible for harmful/noxious compounds as well as organic matter to enter the distribution system. Investigations in a pilot and three full-scale water treatment plants were carried out in order to elucidate the degree of trichome truncation across different unit processes. It was found that genera (Pseudanabaena, Planktolyngbya) with short trichomes (<10-12 cells per trichome), are hardly affected by the unit processes (loss of one to four cells respectively), while genera (Planktothrix, Geitlerinema, Dolichospermum) with longer trichomes (30+ cells per trichome) suffer from high degrees of truncation (up to 63, 30, and 56 cells per trichome respectively). The presence of a rigid sheath and/or mucilaginous layer appears to offer some protection from truncation. It was observed that certain unit processes alter the sensitivity or resilience of trichomes to disruption by physical stress. Some genera (Planktothrix, Geitlerinema) were sensitive to pre-oxidation making them more susceptible to shear stress, while Dolichospermum sp. appears more robust after pre-oxidation. While the potential of toxicogenic genera breaking through into the product water is a real danger, in the current study no toxicogenic cyanobacteria were observed. This work stresses the need for plant operators to study the incoming cyanobacterial composition in the raw water in order to adjust treatment parameters and thus limit the potential of toxic/noxious compound breakthrough.


Assuntos
Cianobactérias/fisiologia , Tricomas/fisiologia , Purificação da Água/métodos , Microcistinas
15.
Mar Pollut Bull ; 141: 550-560, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30955767

RESUMO

The relative importance of organic nitrogen (ON) and inorganic nitrogen (IN) as nitrogen sources for the phytoplankton communities were studied through a seasonal time series of nitrogen species in the eastern Arabian Sea. Seasonal data on nitrogen species showed that ON dominates the system throughout the year and account for >90% of the total nitrogen (TN) during north east monsoon (NEM). The average ON concentration in the study region was 11.5 µM during NEM as compared to 7.2 µM during south west monsoon (SWM). The contribution of picoplankton to the total phytoplankton pool (fpico) increased from 19% during SWM to 36% in NEM. Along with cyanobacteria, the diatoms Thalassionema nitzchoides and Thalassiosira sp. and among the dinoflagellates Pronoctiluca sp. were found to proliferate in ON rich waters. We suggest atmospheric deposition, riverine-input, resuspension of bottom sediment and ground water intrusion as the possible sources of ON in the study region.


Assuntos
Nitrogênio/análise , Fitoplâncton/fisiologia , Cianobactérias/fisiologia , Diatomáceas/fisiologia , Dinoflagelados/fisiologia , Monitoramento Ambiental , Índia , Oceano Índico , Estações do Ano
16.
Sci Total Environ ; 671: 329-338, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-30933789

RESUMO

Hydrodynamic conditions are closely related to the development and dissipation of cyanobacterial blooms. The morphological features of Dolichospermum under different hydrodynamic conditions were analysed during three blooms in Gaoyang Lake, which is part of the backwater area of the China Three Gorges Reservoir, from 2007 to 2010. The results showed that the length of filaments and the morphology of cells were different in relation to the turbulence caused by the difference in hydraulic retention times. Thus, it was hypothesized that turbulence could shape the morphology and physiology of cyanobacteria. To answer the question regarding what the morphological and physiological responses of cyanobacteria to turbulent mixing mean for these organisms, laboratory experiments in continuous cultivation under different dilution rates were conducted to analyse the effects of specific turbulence intensity on the growth, nutrient uptake and morphology of Dolichospermum flos-aquae. Increasing the turbulence intensity caused synchronous increases in the ratio of the cellular length to the width, in the specific surface area of the filament and the cell and in the nutrient uptake rate; at the same time, the average filament length decreased. These indicated that the turbulence, within the range of our experimental design, could stimulate the growth of Dolichospermum by increasing its nutrient uptake. Additionally, at a high specific growth rate, the nutrient uptake rate of Dolichospermum changed more noticeably with the increasing morphological indicators, indicating that the rapidly growing Dolichospermum was more sensitive to turbulence. These findings explain the role of morphological strategies in the dominance of Dolichospermum within a certain range of turbulence intensity, especially in the early growth stage of blooms. The results also facilitate a greater understanding of the hydrodynamic effects on cyanobacteria and will be instrumental in developing flow regulation to control cyanobacterial blooms in reservoirs.


Assuntos
Cianobactérias/fisiologia , Eutrofização , Lagos/microbiologia , China , Cianobactérias/citologia , Monitoramento Ambiental , Hidrodinâmica , Nutrientes/metabolismo
17.
Sci Total Environ ; 669: 29-40, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30877958

RESUMO

In aquatic ecosystems, both phytoplankton and bacteria play pivotal roles. Based on 16S rRNA gene sequencing, considerable research focused on phytoplankton colony attached and free-living bacteria has revealed the close relationship between them, and indicated that the entire bacterial community mediates crucial biogeochemical processes in aquatic ecosystems. However, our understanding of their distribution patterns and response to environmental factors remains poor. Besides, picocyanobacteria, which were omitted from attached bacteria analysis, were reported to be important in cyanobacterial blooms. To explore the spatiotemporal variation of the entire bacterial community with their driving environmental factors and detect the relationships among them, we collected 61 water samples spanning one year and the entire Lake Taihu regions for surveying the entire bacterial community. Our results indicated: 1) seasonal variation of the bacterial community composition was stronger than spatial variation due to the clearly seasonal variation of Microcystis, Synechococcus (pico-cyanobacteria) and other bacteria (Actinomycetales, Pirellulaceae and Sphingobacteriaceae); 2) the spatial distribution of the bacterial community showed that different phyla were dominant in different regions; 3) the bacterial co-occurrence networks varied seasonally and were dominated by Microcystis, ACK-M1, Chthoniobacteraceae, Synechococcus, Pirellulaceae and Pelagibacteraceae; 4) phytoplankton density, chlorophyll a, water temperature and total nitrogen were the major factors that drove the spatiotemporal variation of bacterial community composition. This study revealed the seasonal succession and spatial distribution of the entire bacterial community in Lake Taihu, providing new insights into the relationship between water bloom-forming cyanobacterial species and other bacteria, and their response to environmental factors in eutrophic freshwater ecosystem.


Assuntos
Cianobactérias/fisiologia , Eutrofização , Lagos/microbiologia , Microbiota , Fitoplâncton/fisiologia , China , RNA Bacteriano/análise , RNA Ribossômico 16S/análise , Estações do Ano , Análise de Sequência de RNA
18.
Mol Plant ; 12(5): 715-725, 2019 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-30818037

RESUMO

Cyanobacteria have evolved various photoacclimation processes to perform oxygenic photosynthesis under different light environments. Chromatic acclimation (CA) is a widely recognized and ecologically important type of photoacclimation, whereby cyanobacteria alter the absorbing light colors of a supermolecular antenna complex called the phycobilisome. To date, several CA variants that regulate the green-absorbing phycoerythrin (PE) and/or the red-absorbing phycocyanin (PC) within the hemi-discoidal form of phycobilisome have been characterized. In this study, we identified a unique CA regulatory gene cluster encoding yellow-green-absorbing phycoerythrocyanin (PEC) and a rod-membrane linker protein (CpcL) for the rod-shaped form of phycobilisome. Using the cyanobacterium Leptolyngbya sp. PCC 6406, we revealed novel CA variants regulating PEC (CA7) and the rod-shaped phycobilisome (CA0), which maximize yellow-green light-harvesting capacity and balance the excitation of photosystems, respectively. Analysis of the distribution of CA gene clusters in 445 cyanobacteria genomes revealed eight CA variants responding to green and red light, which are classified based on the presence of PEC, PE, cpcL, and CA photosensor genes. Phylogenetic analysis further suggested that the emergence of CA7 was a single event and preceded that of heterocystous strains, whereas the acquisition of CA0 occurred multiple times. Taken together, these results offer novel insights into the diversity and evolution of the complex cyanobacterial photoacclimation mechanisms.


Assuntos
Aclimatação/efeitos da radiação , Cianobactérias/fisiologia , Cianobactérias/efeitos da radiação , Luz , Ficobilinas/metabolismo , Ficobilissomas/metabolismo , Ficocianina/metabolismo , Cor , Cianobactérias/genética , Cianobactérias/metabolismo , Evolução Molecular , Família Multigênica/genética , Mutação
19.
World J Microbiol Biotechnol ; 35(3): 51, 2019 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-30852691

RESUMO

Protected cultivation of vegetables is often hampered by declining nutrient availability in soil due to year-around farming, which in turn, leads to poor quality and yields, causing serious concern. Our study aimed towards evaluating the potential of novel biofilm formulations-Anabaena or Trichoderma as matrices with Azotobacter sp. as Anabaena-Azotobacter (An-Az) and Trichoderma-Azotobacter (Tr-Az) or together as Anabaena-Trichoderma (An-Tr), on the growth, physiological activities, yield, and changes in the profiles of soil microbial communities in two cultivars (cv. DAPC-6 and cv. Kian) of cucumber (Cucumis sativus). Photosynthetic pigments, evaluated as an index of growth showed two-threefold increase, while elicited activity of defense and antioxidant enzymes was stimulated; this facilitated significant improvement in the plants belonging to the inoculated treatments. Microbial biomass carbon and polysaccharides in soil enhanced by two-threefolds in treatments receiving microbial formulations. Available N in soil increased by 50-90% in An-Az and An-Tr biofilm inoculated treatments, while the availability of P and organic C content of soil improved by 40-60%, over control. PCR-DGGE profiles generated revealed signification modulation of cyanobacterial communities and cultivar-specific differences. Significant enhancement in leaf chlorophyll pigments, soil microbiological parameters and nutrient bio-availabilities along with positive correlation among the analysed parameters, and distinct profiles generated by PCR-DGGE analyses illustrated the promise of these novel inoculants for cucumber.


Assuntos
Inoculantes Agrícolas/fisiologia , Cucumis sativus/crescimento & desenvolvimento , Cucumis sativus/microbiologia , Nutrientes/metabolismo , Desenvolvimento Vegetal , Microbiologia do Solo , Solo/química , Inoculantes Agrícolas/classificação , Anabaena/fisiologia , Azotobacter/fisiologia , Biofilmes/crescimento & desenvolvimento , Biomassa , Carbono , Clorofila , Cianobactérias/fisiologia , Microbiota , Folhas de Planta , Trichoderma/fisiologia
20.
Nat Commun ; 10(1): 1169, 2019 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-30862830

RESUMO

Viruses provide top-down control on microbial communities, yet their direct study in natural environments was hindered by culture limitations. The advance of bioinformatics enables cultivation-independent study of viruses. Many studies assemble new viral genomes and study viral diversity using marker genes from free viruses. Here we use cellular metatranscriptomics to study active community-wide viral infections. Recruitment to viral contigs allows tracking infection dynamics over time and space. Our assemblies represent viral populations, but appear biased towards low diversity viral taxa. Tracking relatives of published T4-like cyanophages and pelagiphages reveals high genomic continuity. We determine potential hosts by matching dynamics of infection with abundance of particular microbial taxa. Finally, we quantify the relative contribution of cyanobacteria and viruses to photosystem-II psbA (reaction center) expression in our study sites. We show sometimes >50% of all cyanobacterial+viral psbA expression is of viral origin, highlighting the contribution of viruses to photosynthesis and oxygen production.


Assuntos
Bacteriófagos/genética , Cianobactérias/fisiologia , Microbiota/fisiologia , Fotossíntese/fisiologia , Fitoplâncton/fisiologia , Bacteriófagos/metabolismo , Cianobactérias/virologia , Genoma Viral/genética , Interações entre Hospedeiro e Microrganismos/fisiologia , Metagenoma/genética , Complexo de Proteína do Fotossistema II/metabolismo , Filogenia , Fitoplâncton/virologia , Água do Mar/microbiologia , Água do Mar/virologia , Análise de Sequência de DNA
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