Host Re-identification of Cyanophage PP and Its Implications for Host Range and Specificity

Dear Editor,In this study,we re-identified the hosts of cyanophage PP.Twenty-three candidate algal strains were tested,and the results indicated that seven strains belonging to Plectonema and Phormidium are the hosts of cyanophage PP,including two previously reported filamentous cyanobacteria,Plectonema boryanum and Phormidium

Observation on Poterioochromonas sp. (Chrysophyte)

Poterrioochromonas sp., isolated from Microcystis cultures in 2002, was described with LM, SEM, TEM. The grazing characteristics of this strain were also observed in laboratory experiments. The results showed that this strain has the representative features of the genus except for the lorica, and the most conspicuous feature of Poterioochromonas sp. was about the chromatophores.

Hydrologic Response of the Climatic Change Based on SWAT Model in Beijiang River Basin

[ Objective] The research aimed to establish SWAT distributed hydrologic model and analyze influence of the climatic change on runoff in Beijiang River basin. [ Method] Beijiang River basin as research object, SWAT model was used to simulate runoff in basin. Monthly water flow in Shijiao station from 1961 to 1980 was used to determine model parameter, while monthly water flow from 1981 to 1990 was used to verify. Setting 15 kinds of climate change scenarios, SWAT model was used to simulate influence of the future climatic change on runoff in Beijiang River basin. [Result] Simulated accuracy of the SWAT model was high, and it could be used to simulate runoff in Beijiang River basin. Under the situation of in- variable rainfall, temperature rise made that evaporation capacity increased, and runoff depth decreased. When temperature unchanged, rainfall increase made that evaporation capacity and runoff depth increased somewhat. [ Conclusion] The research could provide reference basis for water re- source management in Beijiang River basin.

Toxicity of the disinfectant benzalkonium chloride(C_(14))towards cyanobacterium Microcystis results from its impact on the photosynthetic apparatus and cell metabolism

Quaternary ammonium compounds(QACs)are commonly used in a variety of consumer and commercial products,typically as a component of disinfectants.During the COVID-19 pandemic,QACs became one of the primary agents utilized to inactivate the SARS CoV-2 virus on surfaces.However,the ecotoxicological effects of QACs upon aquatic organisms have not been fully assessed.In this study,we examined the effects of a widely used QAC(benzalkonium chloride-C_(14),BAC-14)on two toxigenic Microcystis strains and one non-toxigenic freshwater Microcystis strain and carried out an analysis focused on primary,adaptive and compensatory stress responses at apical(growth and photosynthesis)and metabolic levels.This analysis revealed that the two toxic Microcystis strains were more tolerant than the non-toxic strain,with 96 hr-EC_(50)values of 0.70,0.76,and 0.38 mg/L BAC-14 for toxigenic M.aeruginosa FACHB-905,toxigenic M.aeruginosa FACHB-469,and non-toxigenic M.wesenbergii FACHB-908,respectively.The photosynthetic activities of the Microcystis,assessed via F_(v)/F_(m) values,were significantly suppressed under 0.4 mg/L BAC-14.Furthermore,this analysis revealed that BAC-14 altered 14,12,and 8 metabolic pathways in M.aeruginosa FACHB-905,M.aeruginosa FACHB-469,and M.wesenbergii FACHB-908,respectively.It is noteworthy that BAC-14 enhanced the level of extracellular microcystin production in the toxigenic Microcystis strains,although cell growth was not significantly affected.Collectively,these data show that BAC-14 disrupted the physiological and metabolic status of Microcystis cells and stimulated the production and release of microcystin,which could result in damage to aquatic systems.

Investigation on cyanobacterial production of the proposed neurotoxinβ-N-methylamino-L-alanine(BMAA)

β-N-methylamino-L-alanine(BMAA)is an environmental neurotoxin thought to be produced by cyanobacteria.However,the cyanobacterial origin of BMAA remains controversial.The detection method and culture conditions of cyanobacteria are often cited as factors behind the discrepancy of published results.We showed previously that BMAA was highly toxic to the cyanobacterium Nostoc PCC 7120,and it is taken up via an amino acid transport system.Using a mutantΔnatAΔbgtA deficient in amino acid transport as a genetic control,we show here that BMAA taken up from the medium can be detected quantitatively at a threshold similar to,or below those reported,but was undetectable in the mutant.The BMAA isomer,2,4-diaminobutanoic acids(DAB),but not BMAA,could be detected in cell free extracts of Nostoc PCC 7120.Long-term(20 days)diazotrophic growth or nonlimiting supply of phosphate,conditions reported to enhance BMAA synthesis,did not lead to the detection of BMAA.An UPLC-MS/MS signal with a similar retention time to BMAA was found after prolonged diazotrophic incubation,but did not have fragment ions of BMAA after further analysis.When extended to 29 different cyanobacterial strains and 6 natural cyanobacterial bloom samples,none of them was found to produce BMAA.The cytotoxicity of BMAA to cyanobacteria,and the lack of a cellular protective mechanism against such toxicity,contradict the presence of a BMAA synthesis pathway in these organisms.More specific methods for BMAA detection in vivo need to be developed to clarify the cyanobacterial origin of BMAA.

A flow cytometer based protocol for quantitative analysis of bloom-forming cyanobacteria(Microcystis) in lake sediments

A quantitative protocol for the rapid analysis of Microcystis cells and colonies in lake sediment was developed using a modified flow cytometer, the CytoSense. For cell enumeration, diluted sediment samples containing Microcystis were processed with sonication to disintegrate colonies into single cells. An optimized procedure suggested that 5 mg dw （dry weight）/mL dilution combined with 200 W x 2 min sonication yielded the highest counting efficiency. Under the optimized determination conditions, the quantification limit of this protocol was 3.3x104 cells/g dw. For colony analysis, Microcystis were isolated from the sediment by filtration. Colony lengths measured by flow cytometry were similar to those measured by microscopy for the size range of one single cell to almost 400 ~tm in length. Moreover, the relationship between colony size and cell number was determined for three Microcystis species, including Microcystisflos-aquae, M. aeruginosa and M. wessenbergii. Regression formulas were used to calculate the cell numbers in different- sized colonies. The developed protocol was applied to field sediment samples from Lake Taihu. The results indicated the potential and applicability of flow cytometry as a tool for the rapid analysis of benthic Microcystis. This study provided a new capability for the high frequency monitoring of benthic overwintering and population dynamics of this bloom-forming cyanobacterium.

Insights into the design of thermoelectric Mg_(3)Sb_(2) and its analogs by combining theory and experiment

Over the past two decades,we have witnessed a strong interest in developing Mg3Sb2 and related CaAl2Si2-type materials for lowand intermediate-temperature thermoelectric applications.In this review,we discuss how computations coupled with experiments provide insights for understanding chemical bonding,electronic transport,point defects,thermal transport,and transport anisotropy in these materials.Based on the underlying insights,we examine design strategies to guide the further optimization and development of thermoelectric Mg3Sb2-based materials and their analogs.We begin with a general introduction of the Zintl concept for understanding bonding and properties and then reveal the breakdown of this concept in AMg2X2 with a nearly isotropic three-dimensional chemical bonding network.For electronic transport,we start from a simple yet powerful atomic orbital scheme of tuning orbital degeneracy for optimizing p-type electrical properties,then discuss the complex Fermi surface aided by high valley degeneracy,carrier pocket anisotropy,and light conductivity effective mass responsible for the exceptional n-type transport properties,and finally address the defect-controlled carrier density in relation to the electronegativity and bonding character.Regarding thermal transport,we discuss the insight into the origin of the intrinsically low lattice thermal conductivity in Mg3Sb2.Furthermore,the anisotropies in electronic and thermal transport properties are discussed in relation to crystal orbitals and chemical bonding.Finally,some specific challenges and perspectives on how to make further developments are presented.

Seasonal dynamics of water bloom-forming Microcystis morphospecies and the associated extracellular microcystin concentrations in large,shallow,eutrophic Dianchi Lake

The increasing occurrence of Microcystis blooms is of great concern to public health and ecosystem due to the potential hepatotoxic microcystins （MCs） produced by these colonial cyanobacteria. In order to interpret the relationships between variations of Microcyst/s morphospedes and extracellular MC concentrations, the seasonal dynamics of phytoplankton community composition, MC concentrations, and environmental parameters were monitored monthly from August, 2009 to July, 2010. The results indicated that Microcystis dominated total phytoplankton abundance from May to December （96%--99% of total biovolume）, with toxic Microcystis viridis and non-toxic Microcystis wesenbergii dominating after July （constituting 65%- 95% of the Microcystis population）, followed by M. viridis as the sole dominant species from November to January （49%--93%）. Correlation analysis revealed that water temperature and nutrient were the most important variables accounting for the occurrence ofM. wesenbergii, while the dominance ofM. viridis was related with nitrite and nitrate. The relatively low content of MCs was explained by the association with a large proportion of M. viriclis and M. wesenbergii, small colony size of Microcystis populations, and low water temperature, pH and dissolved oxygen. The extracellular MC （mean of 0.5 ± 0.2 μg/L） of water samples analyzed by enzyme-linked immunosorbent assay （ELISA） demonstrated the low concentrations of MC in Dianchi Lake which implied the low potential risk for human health in the basin. The survey provides the first whole lake study of the occurrence and seasonal variability of Microcyst/s population and

Influence of sunlight on the proliferation of cyanobacterial blooms and its potential applications in Lake Taihu, China

To learn the relationship between sunlight intensity and cyanobacterial proliferations for the further control of the heavy blooms, enclosure experiment were conducted in Meiliang Bay, Lake Taihu by regulating the natural light intensities with different shading ratio （0% （full sunlight）, 10%, 25%, 50% and 75% of original natural sunlight intensities） from September to November in 2010. The results indicated that phytoplankton biomass （mean） decreased significantly when the shading ratios reached 50% or more. Higher shading ratios （e.g. 75%） were very efficient in controlling the average and total cyanobacterialbloom biomass, while 50% shading ratio was proven very effective either in controlling the peak value of phytoplankton biomass or postponing the occurrence of cyanobacterial blooms in Lake Talhu. In addition, phytoplankton composition and photosynthesis efficiency were also affected by altering the shading ratios, and in turn, they might also act on phytoplankton growth. Based on the results from the present study, intermediate shading strategies such as regulation of water level or turbidity through the hydrology regulations would probably be an effective and efficient method in controlling cyanobacterial blooms in large and shallow lakes.

Photocatalytic properties of hierarchical BiOXs obtained via an ethanol-assisted solvothermal process

In this study, bismuth oxyhalide（Bi OXs（X_Cl, Br, I）） semiconductors were prepared by a simple solvothermal method, with ethanol serving as solvent and a series of tetrabutylammonium halide surfactants as halogen sources. Under identical synthetic conditions, Bi OBr was more readily constructed into regular flower-like hierarchical architectures. The photocatalytic properties of the materials were studied by monitoring the degradation of rhodamine B（Rh B）,with visible light absorption, and colorless salicylic acid（SA）. It was found that both Rh B and SA were rapidly degraded on the surface of Bi OBr. Bi OCl was rather active for the degradation of Rh B,but ineffective toward the degradation of SA. However, neither Rh B nor SA could be degraded effectively in the case of Bi OI. Further experiments such as UV–visible spectroscopy and detection of U OH and O2 Uradicals suggest that the electronic structure of the Bi OX photocatalysts is responsible for the difference in their activities.

Submerged vegetation removal promotes shift of dominant phytoplankton functional groups in a eutrophic lake

Historical data indicate that the dominance of submerged plants in Dianchi Lake in the 1960 s was characterized by low algal density with dominance of non-toxic group J（Scenedesmus,Pediastrum,etc.）. The removal of submerged plants,which began in the 1970 s,resulted in the expansion of bloom-forming Microcystis（group M）. Laboratory experiments suggested that Microcystis aeruginosa was inclined to grow and develop at elevated temperatures. The growth of Scenedesmus obliquus was slower than that of co-cultivated M. aeruginosa in the absence of Ceratophyllum demersum,especially at higher temperatures. The existence of submerged plant C. demersum could inhibit the growth of the harmful algae M. aeruginosa and this inhibitory effect by C. demersum was enhanced with an increase in temperature. Instead,with C. demersum,the growth of S. obliquus was not inhibited,but the co-cultivated M. aeruginosa was eliminated in a short time. Combined with the historical data and laboratory experiments,it was indicated that the submerged plants might play important roles in the dominance of the non-toxic group J in the historical succession. Consequently,the introduction of the submerged plant such as C. demersum might alter the dominant phytoplankton functional groups from M to J and benefit the restoration of the eutrophic lake.

Simultaneous elimination of cyanotoxins and PCBs via mechanical collection of cyanobacterial blooms:An application of“green-bioadsorption concept”

In this study,the distribution,transfer and fate of both polychlorinated biphenyls（PCBs）and cyanotoxins via phytoplankton routes were systematically investigated in two Chinese lakes.Results indicated that PCB adsorption/bioaccumulation dynamics has significantly positive correlations with the biomass of green alga and diatoms.Total lipid content of phytoplankton is the major factor that influences PCB adsorption/bioaccumulation.Cyanobacterial blooms with relatively lower lipid content could also absorb high amount of PCBs due to their high cell density in the water columns,and this process was proposed as major route for the transfer of PCBs in Chinese eutrophic freshwater.According to these findings,a novel route on fates of PCBs via phytoplankton and a green bioadsorption concept were proposed and confirmed.In the practice of mechanical collections of bloom biomass from Lake Taihu,cyanotoxin/cyanobacteria and PCBs were found to be removed simultaneously very efficiently followed this theory.

Microcystin-degrading bacteria affect mcy D expression and microcystin synthesis in Microcystis spp

Cyanobacterial blooms occur increasingly often and cause ecological,economic and human health problems worldwide.Microcystins（MCs）are the dominant toxins produced by cyanobacteria and are implicated in epidemic disease and environmental problems.Extensive research has been reported on the various regulating factors,e.g.,light,temperature,nutrients such as nitrogen and phosphorus,p H,iron,xenobiotics,and predators,that influence microcystin（MC）synthesis,but little is known about the effects of cyanobacteria-associated bacteria on MC synthesis.A considerable number of studies have focused on interactions between Microcystis species and their associated bacteria.In this study,we evaluated the effects of MC-degrading bacteria（MCDB）on MC synthesis gene mcy D expression and MC synthesis in axenic strain PCC7806,non-axenic strain FACHB905,and colony strain FACHB1325 of Microcystis by quantitative real-time polymerase chain reaction（RT-PCR）assay and enzyme-linked immunosorbent assay（ELISA）.We demonstrate for the first time that MCDB can induce and up-regulate the MC production and transcriptional response of the mcy D gene of toxic Microcystis.On day 4 of the culturing experiment,the intracellular MC concentration and transcriptional response of mcy D of FACHB1325 were up-regulated 1.9 and 5.3-fold over that of the control,and for FACHB905 were up-regulated 1.8 and 4.2-fold over that of the control,respectively.On day 10,the transcriptional response of mcy D was up-regulated 21.3-fold in PCC7806.These results indicate that there are interactions between toxic Microcystis and MCDB,and MCDB may play a role in regulating mcy D expression in toxic Microcystis.

Protist 10,000 Genomes Project

Protists are a highly diverse group of microscopic eukaryotic organisms that are not fungi,animals,or plants.Protistswere some of the microbes first visualized and described by Anton van Leeuwenhoek using themicroscope in the seventeenth century.After that,the description and cataloging of these diverse microbial eukaryotes was pursued by microbiologists throughout the following centuries.1 So far,more than 60,000 protist species have been recorded in the NCBI taxonomy system,but many have yet to be identified.Protists have long been considered important models in fundamental biological studies,such as cell biology,genetics,ecology and evolution toxicology,and applied fields,including biofuels,nutritional supplements and aquaculture feed production,environmental monitoring and pollution treatment,protozoan parasitic disease treatment and prevention,as well as agriculture.