Impact of environmental pollution on cyanobacterial proline content

This study describes the toxic effects of different prominent aquatic pollutants—heavy metals (Cd & Pb), pesticides (alphamethrin and deltamethrin) and salt (NaCl)—on the intracellular proline content in the cyanobacterium, Westiellopsis prolifica–Janet strain–NCCU331. Despite a reduction in growth (measured as chlorophyll a content), the intracellular proline content increased in the presence of heavy metals, pesticides and high salt concentration. The intracellular cyanobacterial proline accumulation was more pronounced under salt stress than in the presence of pesticides and heavy metals. We have also compared whether or not anionic components influence heavy metal toxicity. It was found that the chlorides of Cd and Pb were more toxic than the NO₃ and the order of toxicity was CdCl₂ > PbCl₂ > Cd (NO₃)₂ > Pb (NO₃)₂. Among pyrethroids, deltamethrin was more toxic than alphamethrin. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Antibacterial, antifungal and cytotoxic activity of terrestrial cyanobacterial strains from Serbia

Cyanobacteria are known to be a rich source of biologically active compounds some of which can have pharmaceutical importance. In this work we present the screening results of cyanobacterial strains for their antibacterial, antifungal, and cytotoxic activity. Cyanobacterial strains were isolated from various soil types in province of Vojvodina and Central Serbia, Republic of Serbia. The screening included 9 strains of Anabaena and 9 strains of Nostoc. Both, extracellular products (from the culture liquid) and cellular crude lipophilic extracts were tested against 13 bacterial strains and 8 fungal strains. Cytotoxic activity was tested against three human cell lines. Methanol extracts were prepared according to ?stensvik. Antibacterial and antifungal activities were determined measuring inhibition zone, 48 h after inoculation. The cytotoxic activity was determined by sulforhodamine B (SRB) colorimetric assay. Of all cyanobacterial strains tested, 52% showed some antifungal and 41% antibacterial activity. Two out of six tested strains possessed cytotoxic activity. The cytotoxic activity of Anabaena strain S12 was found both in culture liquid and crude cell extract. It occurred specifically between the 21st and 42nd day of cultivation against HeLa and MCF7 cells, but had no activity against cell line derived from a healthy tissue. A high percentage of the active strains among the tested strains justify the effort of screening cyanobacteria that are isolated from terrestrial environments. The most promising strains for the fur- ther study are Anabaena strain S12 which showed strong cytotoxic and antibacterial activity and Ana- baena strain S20 which produces a potent antifungal compound. The future work, besides further screening and chemical identification of the active compounds, should also include the development of culture techniques that would lead to more efficient production of biologically active compounds.     

Influence of light on phycobiliprotein production in three marine cyanobacterial cultures

Complementary chromatic adaptation, a photomorphogenetic response, known to occur in many cyanobacteria, enables them to efficiently absorb prevalent wavelengths of light in the environment. In the present study, we have described the influence of light on phycobiliprotein production in three marine phycoerythrin producing cyanobacterial cultures, namely, Lyngbya sp. A09DM, Phormidium sp. A27DM and Halomicronema sp. A32DM. A comparative study (UV-visible overlay spectra and SDS-PAGE analyses) of phycobiliproteins purified from all the three cultures grown in white, yellow, red and green lights has been confirmed. White light was taken as control. Red and green lights were taken to check their effect on phycocyanin and phycoerythrin production, respectively. Yellow light was studied as its wavelength falls in between green and red light. Lyngbya sp. A09DM was found to be the best chromatically adapting cyanobacterium followed by Halomicronema sp. A32DM. These two cultures can be placed in group III chromatic adaptors. Phormidium sp. A27DM was the least chromatically adapting culture and can be placed in group II chromatic adaptors. The study signifies that even light plays an important role along with nutrient availability in adapting cultures to changing environmental conditions.     

土壤干旱条件下氮素营养对玉米内源激素含量影响

在田间持水量分别保持于35％、55％和75％±5％的土壤水分条件下,利用盆栽实验研究了土壤干旱和氮素营养对玉米内源激素和气孔导度的影响．结果表明,土壤干旱下氮素营养明显降低了玉米根系木质部汁液ABA浓度,而正常供水下施氮处理间则无显著差异(施氮处理仍较低),同时测定的叶片ABA浓度则呈相反的变化趋势,表现为干旱下施氮处理要高于不施氮处理;施氮处理木质部汁液中ZRs浓度应低于相应的不施氮处理,在调控气孔行为方面并未表现拮抗ABA作用;3种土壤水分条件下,施氮玉米叶片的气孔导度均高于不施氮处理,与木质部汁液ABA浓度呈负相关,说明施氮处理较低的根源ABA浓度是导致其气孔导度较大的主要原因．     

Evaluation of growth and phycobiliprotein composition of cyanobacteria isolates cultivated in different nitrogen sources

Phycobiliproteins, light-harvesting pigments found in cyanobacteria and in some eukaryotic algae, have numerous commercial applications in food, cosmetic, and pharmaceutical industries. Colorant production from cyanobacteria offers advantages over their production from higher plants, as cyanobacteria have fast growth rate and high photosynthetic efficiency and require less space. In this study, three cyanobacteria strains were studied for phycobiliprotein production and the influence of sodium nitrate, potassium nitrate and ammonium chloride on the growth and phycobiliprotein composition of the strains were evaluated. In the batch culture period of 12 days, Phormidium sp. and Pseudoscillatoria sp. were able to utilize all tested nitrogen sources; however, ammonium chloride was the best nitrogen source for both strains to achieve maximum growth rate μ?=?0.284?±?0.03 and μ?=?0.274?±?0.13 day^?1, chlorophyll a 16.2?±? 0.5 and 12.2?±? 0.2 mg L^?1, and phycobiliprotein contents 19.38?±?0.09 and 19.99?±?0.14% of dry weight, whereas, for Arthrospira platensis, the highest growth rate of μ?=?0.304?±?0.0 day^?1, chlorophyll a 19.1?±?0.5 mg L^?1, and phycobiliprotein content of 22.27?±?0.21% of dry weight were achieved with sodium nitrate. The phycocyanin from the lyophilized cyanobacterial biomass was extracted using calcium chloride and food grade purity (A₆₂₀/A₂₈₀ ratio >?0.7) was achieved. Furthermore, phycocyanin was purified using two-step chromatographic method and the analytical grade purity (A₆₂₀/A₂₈₀ ratio >?4) was attained. SDS-PAGE demonstrated the purity and presence of two bands corresponding to α- and β-subunits of the C-phycocyanin. The results showed that Phormidium sp. and Pseudoscillatoria sp. could be good candidates for phycocyanin production.     

Effects of extreme drought on terrestrial ecosystems: review and prospects

作为地球表层重要的组成部分, 陆地生态系统是人类生存和发展的重要场所。进入21世纪以来, 气候变化导致干旱事件发生的强度、频度和持续时间显著增加, 对陆地生态系统带来深远的影响, 严重制约甚至威胁人类社会的可持续发展。因此, 开展极端干旱对陆地生态系统影响的研究并评估其生态风险效应, 是当前全球变化领域研究的重点问题。该文从植物生理生态过程、生物地球化学循环、生物多样性以及生态系统结构和功能4个方面综述了极端干旱对陆地生态系统的影响, 并对当前的研究热点进行探讨, 深度剖析当前研究中存在的难点问题和未来可能的发展方向, 以期为未来开展干旱对陆地生态系统影响的观测与预测研究提供参考, 为在未来干旱影响下加强陆地生态系统风险评估和管理提供新思路。     

Quantifying photosynthetic capacity and its relationship to leaf nitrogen content for global-scale terrestrial biosphere models

Photosynthetic capacity and its relationship to leaf nitrogen content are two of the most sensitive parameters of terrestrial biosphere models (TBM) whose representation in global‐scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Here, we use data of qualitative traits, climate and soil to subdivide the terrestrial vegetation into functional types (PFT), and then assimilate observations of carboxylation capacity, V_max (723 data points), and maximum photosynthesis rates, A_max (776 data points), into the C₃ photosynthesis model proposed by Farquhar et al. to constrain the relationship of (V_max normalised to 25 °C) to leaf nitrogen content per unit leaf area for each PFT. In a second step, the resulting functions are used to predict per PFT from easily measurable values of leaf nitrogen content in natural vegetation (1966 data points). Mean values of thus obtained are implemented into a TBM (BETHY within the coupled climate–vegetation model ECHAM5/JSBACH) and modelled gross primary production (GPP) is compared with independent observations on stand scale. Apart from providing parameter ranges per PFT constrained from much more comprehensive data, the results of this analysis enable several major improvements on previous parameterisations. (1) The range of mean between PFTs is dominated by differences of photosynthetic nitrogen use efficiency (NUE, defined as divided by leaf nitrogen content), while within each PFT, the scatter of values is dominated by the high variability of leaf nitrogen content. (2) We find a systematic depression of NUE on certain tropical soils that are known to be deficient in phosphorous. (3) of tropical trees derived by this study is substantially lower than earlier estimates currently used in TBMs, with an obvious effect on modelled GPP and surface temperature. (4) The root‐mean‐squared difference between modelled and observed GPP is substantially reduced.     

Influence of source of organics and soil organic matter content on cyanobacterial nitrogen fixation and distributional pattern under different water regimes

Organic substances viz., sewage and slurry, compost, farmyard manure (FYM) and green manure used in the study under different moisture regimes had a varied effect on cyanobacterial nitrogenase activity and its distributional pattern. Green manure source was the most effective in enhancing cyanobacterial nitrogenase activity, followed by FYM, compost and sewage and slurry. A better response was observed in soils under waterlogged than under moist conditions. A gradual increase in nitrogenase activity was recorded up to one per cent organic carbon both in vitro and in vivo. The cyanobacterial diversity was maximum in sewage and slurry sites.     

Consortial N2 fixation: a strategy for meeting nitrogen requirements of marine and terrestrial cyanobacterial mats

Abstract: Four microbial mat-forming, non-axenic, strains of the non-heterocystous, filamentous, cyanobacterial genus Microcoleus were maintained in culture and examined for the ability to fix atmospheric nitrogen (N₂). Each was tested for nitrogenase activity using the acetylene reduction assay (ARA) and for the presence of the dinitrogenase reductase gene ( nifH ), an essential gene for N₂ fixation, using the polymerase chain reaction (PCR). The Microcoleus spp. cultures were incapable of growth without an exogenous nitrogen source and never exhibited nitrogenase activity. Attempts to amplify a 360-bp segment of the nifH gene using DNA purified from the cyanobacterial cultures did not produce any cyanobacteria-specific nifH sequences. However, several non-cyanobacterial homologous nifH sequences were obtained. Phylogenetic analysis showed these sequences to be most similar to sequences from heterotrophic bacteria isolated from a marine microbial mat in Tomales Bay (California, USA), and bulk DNA extracted from a cryptobiotic soil crust in Moab (Utah, USA). Microcoleus spp. dominated the biomass of both systems. Cyanobacteria-specific 16S rDNA sequences obtained from the cultured cyanobacterial strains demonstrate that the lack of cyanobacteria-specific nifH sequences was not due to inefficiency of extracting Microcoleus DNA. Hence, both the growth and genetic data indicate that, contrary to earlier reports, Microcoleus spp. appear incapable of fixing N₂ because they lack at least one of the requisite genes for this process. Furthermore, our study suggests epiphytic N₂-fixing bacteria form a diazotrophic consortium with these Microcoleus spp. and are likely key sources of fixed N₂ generated within soil crusts and marine microbial mats.     

陆地和淡水生态系统新型微生物氮循环研究进展

氮生物地球化学循环是地球物质循环的重要枢纽,是决定陆地生态系统生产力水平、水资源安全、温室气体生成排放的关键过程。氮循环是由微生物介导的一系列复杂过程,不同形态、价态氮化合物的转化分别由相应的功能微生物驱动完成。随着厌氧氨氧化、完全氨氧化等新型氮转化过程的相继报道和发现更新了人们对氮循环的认识。本文综述了陆地和淡水生态系统中厌氧氨氧化(anammox)、硝酸盐异化还原为铵(DNRA)、完全氨氧化(comammox)等新型氮循环过程的发生机制、热区分布及环境效应,并总结了这三种氮循环的相互关系。     

Intra-specific phenotypic and genotypic variation in toxic cyanobacterial Microcystis strains

Aims:  We determined if the intra-specific genetic diversity of Microcystis aeruginosa correlates with phenotypic characteristics.
Methods and Results:  Microcystis aeruginosa isolates from various Japanese waters were characterized using genetic analyses based on the 16S–23S rDNA internal transcribed spacer (ITS) region and DNA-independent RNA polymerase ( rpoC1 ) gene sequences. In addition, morphological and biochemical properties, and the toxicity of M. aeruginosa strains were determined. We found a correlation in phylogenetic clusters of the ITS region and rpoC1 gene sequences. Using a polyphasic approach, genotypic and phenotypic variations in M. aeruginosa showed that the three genetic lineage groups are comprised of a particular phenotype or subgroup of closely related phenotypes. However, some strains had high phenotypic and genotypic diversity compared to the three lineage groups and did not show distinct lineages; therefore, these strains were designated as the 'complex group'.
Conclusions:  The 'complex group' consisted of genetically and phenotypically incoherent and high diverse populations in M. aeruginosa , although some genotypes or lineages displayed consistent phenotypes.
Significance and Impact of the Study:  The polyphasic approach combining phenotypic and genetic characterization was effective for comprehending distinct lineages and discriminating the potential complexity of M. aeruginosa populations at the intra-species level.     

Toxicity of organotins towards cyanobacterial photosynthesis and nitrogen fixation

Abstract Inhibition of photosynthesis by a range of organotin compounds in Plectonema boryanum was concentration-dependent and decreased in the order tributyltin (Bu₃SnCl) > tripropyltin (Pr₃SnCl) ≥ dibutyltin (Bu₂SnCl₂) ≥ triphenyltin (Ph₃SnCl) > triethyltin (Et₃SnCl) > trimethyltin (Me₃SnCl) > monobutyltin (BuSnCl₃). IC₅₀ values were determined for the most toxic organotin species and varied from approximately 1.2 μM for Bu₃SnCl to approximately 13 μM for Ph₃SnCl. A similar order of inhibition of photosynthesis was observed in Anabaena cylindrica , although here IC₅₀ values were slightly lower (e.g. approximately 1 μM for Bu₃SnCl and 5 μM for Ph₃SnCl).Nitrogenase activity was generally more sensitive to inhibition by organotin compounds than photosynthesis in A. cylindrica and this was particularlyy evident for Bu₂SnCl₂; approximate IC₅₀ values for Bu₂SnCl₂ were 3 and 9 μM, as estimated by nitrogenase activity and photosynthesis, respectively. These results indicate that organotin compounds have the potential to inhibit cyanobacterial metabolism in aquatic systems.     

陆地生态系统可溶性有机氮研究进展

可溶性有机氮(dissolved organic nitrogen DON)的流动是陆地生态系统氮循环的重要组成部分。本文就陆地生态系统DON的来源、组成、性质;森林生态系统DON的流动、季节动态以及DON在氮循环中的地位等方面作了概括和探讨。今后的陆地生态系统DON的研究应该集中在以下几个方面：确定陆地生态系统中DON的各分室DON的浓度、流量;DON的源与汇问题;量化不同生态系统中DON库的大小和组成;研究DON在氮的矿化、微生物的固持、以及植物吸收等氮循环过程中的地位;对比研究DON与DOC(dissolved organic carbon)的动态差别;探讨DON与植物营养和碳积累的关系等。     

Enhancement of cyanobacterial salt tolerance by combined nitrogen

Presence of certain nitrogenous compounds in the growth medium significantly enhanced the salt tolerance of the fresh-water cyanobacterium Anabaena sp. strain L-31 as well as the brackish water cyanobacterium Anabaena torulosa. Among these, nitrate, ammonium, and glutamine were most effective followed by glutamate and aspartate. These nitrogenous compounds also inhibited Na⁺ influx in both Anabaena spp. with the same order of effectiveness as that observed for protection against salt stress. The inhibition of Na⁺ influx on addition of the nitrogenous substances was rapid; nitrate and ammonium inhibited Na⁺ influx competitively. Proline and glycine did not affect Na⁺ influx and also had no influence on the salt tolerance of either Anabaena sp. The observed protection was not consequent to a stimulatory effect of combined nitrogen on growth per se. Uptake of NO₃⁻ and NH₄⁺ increased during salt stress but was not correlated with growth. Intracellular levels of NO₃⁻ and NH₄⁺ were found to be inadequate to constitute a major component of the internal osmoticum. The results suggest that inhibition of Na⁺ influx by combined nitrogen is a major mechanism for protection of cyanobacteria against salt stress.     

Light intensity adaptation of the phycobiliprotein content of the red alga Porphyridium

In the unicellular red algae Porphyridium cruentum and P. aerugineum the phycobiliprotein content of the plastids is regulated by the applied energy fluence rate. Cells cultured at low energy fluence rates (220 W cm^-2) posses up to three times more phycobiliproteins than cells grown at high energy fluence rates (3200 W cm^-2). These values were obtained by direct measurement of the apoprotein of the phycobiliproteins. Transfer of cells from low to high energy fluence rates and vice versa results in an adaptation of the phycobiliprotein content to the new light conditions. This process starts immediately after the transfer of the cells and requires several days. On the other hand, the amount of the enzyme ribulose-1,5-bisphosphate carboxylase, which is also a prominent protein of the plastids of red algae, does not change significantly in response to differing fluence rates.Abbreviation RuBPCase ribulose-1,5-bisphosphate carboxylase/oxygenase     

Effect of grazing by a neotropical copepod, Notodiaptomus, on a natural cyanobacterial assemblage and on toxic and non-toxic cyanobacterial strains

The neotropical, freshwater copepod Notodiaptomus iheringi decreasedthe growth of small colonies in cyanobacteria-dominated plankton,indicating that they can be efficiently ingested and that theymay represent an important food source for this copepod in reservoirsdominated by cyanobacteria. Cultured, colonial, toxic Microcystisaeruginosa was not affected, indicating that toxicity may causea decrease in its ingestion by N. iheringi.