Orthophosphate uptake of planktonic microorganisms in Lake Balaton

Seasonal orthophosphate uptake of natural plankton has been studied in hypertrophic and mesotrophic basins of Lake Balaton. Initial uptake of carrier-free labelled phosphoric acid followed first order kinetics in accordance with a single two-compartment model. In isotope equilibrium from 1.2 to 9.7 per cent of radioactivity was found in the filtrate. Turnover times of orthophosphate in water were some minutes in summer and two orders of magnitude longer in winter and April. Turnover time of phosphorus in microorganisms has been estimated on the basis of equilibrium isotope distribution between water and particular phases and turnover time in water. It ranged from 28 to over 1 000 min. The shortest times were found in summer, and the longest in winter. Turnover time of orthophosphate in water increased in relation to phosphate additions according to Michaelis-Menten kinetics. The values of Michaelis-constant plus the ambient orthophosphate concentration (K + S_n) suggested an overestimation of real phosphate concentrations by chemical measurements, being much lower than soluble reactive phosphorus contents in most cases, as it is well-known in many other lakes. Both K + S_n values and maximum uptake velocities (V) were significantly higher in the hypertrophic basin than in the mesotrophic one, in contrast to essentially similar values of turnover times. Maximum uptake velocity per unit chlorophyll-a P _opt:V ratio showed extreme to moderate phosphorus deficiency for Lake Balaton plankton, which seemed to decrease somewhat in the course of eutrophication.     

Determination of the Limiting Plant Nutrient in the Water of Lake Balaton by Algal Assay Procedure

Algal assays were performed on water samples taken from different sites in Lake Balaton. Selenastrum capricornutum was used in the test to determine the primarily limiting plant nutrient. The results of supplementary nutrient additions to the bottle tests were evaluated by cell counts. The tests have indicated phosphorus as growth rate limiting, and in two cases as biomass limiting plant nutrient, but periodic occurrences of nitrogen limitation cannot be excluded.     

Seasonal and habitat-related distribution pattern of Synechococcus genotypes in Lake Constance

The abundance and distribution of Synechococcus spp. in the autotrophic picoplankton of Lake Constance, were followed in the pelagic and littoral habitat by qPCR over 2 years. One genotype, represented by isolated phycoerythrin-rich strain BO 8807, showed a seasonal distribution pattern in both habitats. Before a stable thermal stratification, the maximum of both the Synechococcus population and genotype BO 8807 occurred at 15 or 20 m water depth in the pelagic habitat. During the summer stratification, when the absolute abundance of all Synechococcus spp. was highest above 15 m, the absolute and relative abundance of genotype BO 8807 was maximal at 20 m. These results indicate that Synechococcus spp. or single genotypes are present in deep maxima in Lake Constance. The in situ dynamics of genotype BO 8807 is consistent with the observation that isolated strain BO 8807 requires higher phosphate concentrations for maximum growth rates than a strain from the same phylogenetic cluster that dominates the pelagic summer population. In contrast to these findings, low genome numbers of phycocyanin-rich genotype BO 8805 were found temporarily only in both the littoral and pelagic plankton. Microscopy revealed that PC-rich cells in general occurred preferentially in the littoral habitat. We discuss our results with respect to the versatility of picocyanobacteria of the evolutionary lineage VI of cyanobacteria, and a habitat-related distribution pattern of Synechococcus genotypes.     

Updating water quality targets for shallow Lake Balaton (Hungary), recovering from eutrophication

The paper presents an overview about recovery of shallow Lake Balaton from eutrophication by assessing quantitative and qualitative changes in phytoplankton, zooplankton, and chironomids as a function of load reduction. The aim was to update the present water quality targets. The proposed targeting scheme supplements the existing one with a range of lake-specific ecological criteria. We conclude that simple targets (desired phytoplankton biomass and permissible load) are the best choice during the initial stage of eutrophication management, but more complex schemes including ecological criteria are needed to trace recovery when re-organization of the ecosystem takes place.     

Ingestion Rates of Some Daphnia Species in a Shallow Lake (Lake Balaton,Hungary)

Filtering rates of three species of Daphnia were studied in situ by the ¹⁴C technique during the summer in a lake with a water temperature of 20-25°C (Lake Balaton, Hungary). The renewal time of gut contents proved to be 3-5 min in each of the three species whether fed on natural or artificial food. From May to September, filtering rates of D. cucullata, D. hyalina and D. galeata averaged 7.8, 10.3 and 9.2 ml ind.⁻¹ day⁻¹, respectively. Identically long individuals of all three species had almost the same filtering rates in spring, whereas in summer animals of identical weights had similar filtering rates regardless of species because of the length variability of the helmets. The grazing rate of adult filter-feeding crustaceans is suggested to be approximately 7 % per day.     

新型聚球藻噬藻体Yong-L2-223的分离及基因组分析

【目的】噬藻体(cyanophages)是特异性侵染蓝藻(cyanobacteria)的病毒，广泛分布于各类水体中，在调节蓝藻种群动态和密度、推动生物地球水生生态系统循环中起着重要作用。本研究的目的在于分离、鉴定噬藻体。【方法】本研究以海洋聚球藻(Synechococcus sp.) PCC 7002为指示宿主，从淡水水样中分离培养一株新型噬藻体Yong-L2-223，对其进行了宿主范围实验、全基因组测序、基因功能注释和系统进化分析。【结果】针对31株供试蓝藻的宿主范围实验，结果除指示藻PCC 7002 [属于聚球藻目(Synechococcales)]外，Yong-L2-223能够感染2株淡水蓝藻，分别是来源于滇池的绿色微囊藻(Microcystis viridis) FACHB-1342 [属于色球藻目(Chroococcales)]和水华束丝藻(Aphanizomenon flos-aquae)FACHB-1209[属于念珠藻目(Nostocales)]。既可在高盐条件下感染海洋蓝藻，又可在低盐条件下感染淡水蓝藻，Yong-L2-223具有广盐性。透射电镜观察表明，Yong-L2...     

Genetic diversity among Synechococcus spp. (cyanobacteria) isolated from the pelagial of Lake Constance

Abstract: Seven phycoerythrin (PE)-rich and six phycocyanin (PC)-rich unicellular cyanobacteria of the Synechococcus type were isolated from the pelagial of Lake Constance. The genetic diversity among the isolates was evaluated using restriction fragment length polymorphism (RFLP) within the psbA gene family. Nine out of 13 isolates exhibit different DNA structures in the probed areas and, furthermore, they differ from morphologically similar strains collected from other lakes. The data set does not support a principal distinction between PC-rich and PE-rich strains but it reveals less heterogeneity in the coding region of the psbA genes among PE-rich isolates than among PC-rich isolates. The isolation of distinct strains in different seasons suggests species diversity and seasonal occurrence of Synechococcus spp. in Lake Constance.     

Growth and antioxidant system of the cyanobacterium Synechococcus elongatus in response to microcystin-RR

Microcystins, one type of the cyanobacterial toxins, show a broad range of hazardous effects on other organisms. Most of the researches on the toxic effects of microcystins have involved in animals and higher plants. Little work, however, has been done on evaluating the mechanisms of microcystin toxicity on algae. In this study, the toxicological effects of microcystin-RR (MC-RR) on the cyanobacterium Synechococcus elongatus were investigated. For this purpose, six physio-biochemical parameters (cell optical density, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione S-transferase (GST)) were tested in algal cells when exposed to 100 g^–1 microcystin-RR. The results showed that the growth of Synechococcus elongatus (expressed as optical density) was significantly inhibited compared with the control. At the same time, the treated algae exhibited a pronounced increase in production of ROS and MDA after 6 days exposure to microcystin-RR. Significant changes in GSH levels and GSH-Px, GSH activities were also detected in algal cells, with higher values being observed in the toxin treated algae after 6 days exposure. GST activities in the treated algae exhibited a decline after exposure and rapid augmentation on day 3, thereafter, they kept at a high level when compared to the control group. GSH contents and GSH-Px activities were also significantly raised in the toxin-treated algae cells from day 3, but they showed a sharp decrease on day 4, which was the onward of cell proliferation. These results suggested that oxidative stress manifested by elevated ROS levels and MDA contents might be responsible for the toxicity of microcystin to Synechococcus elongatus and the algal cells could improve their antioxidant ability through the enhancement of enzymatic and non-enzymatic preventive substances.     

Diel Division Cycle and Growth Rates of Synechococcus in Lakes Huron and Michigan1

A clone of Synechococcus isolated from Lake Huron and natural populations of Synechococcus from lakes Huron and Michigan were studied in 1989 to examine the diel division cycle and to provide estimates of the in situ growth rate based on the frequency of dividing cells (FDC) method. Cultured populations of Synechococcus exhibited a consistent diel division pattern with a midday/afternoon (1100–1800 h) peak in the percent of dividing cells. The maximum percent of dividing cells varied among cultures (8-27%) and was related to the growth rate. A small fraction of dividing cells (3-5%) remained throughout the dark period, suggesting that some cells were arrested in the doublet stage prior to division. The duration of division (t_d) ranged from 2.6-4.9 h, with a 3.7 h mean for cultures with growth rates ≥0.34 d⁻¹ but increased to 8 h at a lower growth rate of 0.20 d⁻¹. The diel division pattern for natural populations was very similar to the laboratory clone; an afternoon peak (1400-2100 h) in dividing cells and a small fraction of dividing cells (2-5%) remained during the dark period. The maximum percent of dividing cells for natural populations ranged from 6-10%. In situ growth rates, determined from the FDC and assuming a constant t_d of 3.7 h, ranged from 0.30-0.42 d⁻¹. The FDC method may provide accurate estimates of in situ growth, particularly in environments where the growth rate is >0.34 d⁻¹, but in lakes Huron and Michigan where growth rates can be lower and t_d values may increase, FDC-growth rates must be viewed with caution.     

Simultaneous Monitoring of Phosphine and of Phosphorus Species in Taihu Lake Sediments and Phosphine Emission from Lake Sediments

Phosphine (PH₃) was monitored in the Taihu Lake in China by a GC/NPD method, coupled with cryo-trapping enrichment technology. Results showed that PH₃ was universally detected in sediments, lake water and atmosphere of the Taihu Lake area. Total phosphorus (TP_s) and fractions of different phosphorus species in lake sediments were separately measured as dissolved phosphate (DP), phosphorus bound to aluminum (Al-P), iron (Fe-P) and calcium (Ca-P), occluded phosphorus (OP), and organic phosphorus (Org-P) by sequential chemical extraction. High PH₃ levels were correlated with high TP_s values in sediments and with eutrophication at different sites. In addition, a positive linear correlation equation was obtained between the concentrations of PH₃ in lake sediments and of the phosphorus fractions. The resulting multiple linear regression equation is PH₃ = −165 + 63.3 DP + 0.736 Al-P + 2.33 Ca-P + 2.29 Org-P. The flux of PH₃ across the sediment–water interface was estimated from sediment core incubation in May and October 2002. The annual average sediment–water flux of PH₃ was estimated at ca. 0.0138±0.005 pg dm⁻² h⁻¹, the average yearly emission value of PH₃ from Taihu Lake sediments to water was calculated to be 28.3±10.2 g year⁻¹, which causes a water PH₃ concentration of up to 0.178±0.064 pmol dm⁻³. The real importance of PH₃ could be higher, because PH₃ could be consumed in the oxic sediment–water boundary layer and in the water column. Spatial and temporal distributions of total phosphorus (TP_w) and chlorophyll a (Chl-a) in the water column of Taihu Lake were measured over the study period. Higher water PH₃ has also been found where the TP_w content was high. Similarly, high Chl-a was consistent with higher water PH₃. Positive relationships between PH₃ and TP_w (average R² = 0.47±0.26) and Chl-a (average R² = 0.23±0.31) were observed in Taihu Lake water.     

Growth engineering of Synechococcus elongatus PCC 7942 for mixotrophy under natural light conditions for improved feedstock production

Synechococcus elongatus PCC 7942 has been widely explored as cyanobacterial cell factory through genetic modifications for production of various value‐added compounds. However, successful industrial scale‐ups have not been reported for the system predominantly due to its obligate photoautotrophic metabolism and use of artificial light in photobioreactors. Hence, engineering the organism to perform mixotrophy under natural light could serve as an effective solution. Thus, we applied a genetically engineered strain of Synechococcus elongatus PCC 7942 expressing heterologous hexose transporter gene (galP) to perform mixotrophy under natural light in a temperature controlled environmental chamber (EC). We systematically studied the comparative performances of these transformants using autotrophy and mixotrophy, which showed 3.4 times increase in biomass productivity of mixotrophically grown transformants over autotrophs in EC. Chlorophyll a yield was found to have decreased in mixotrophic conditions, possibly indicating reduced dependency on light for energy metabolism. Although pigment yield decreases under mixotrophy, titer was found to have improved due to increased biomass productivity. Carotenoid analysis showed that zeaxanthin is the major carotenoid produced by the species which is essential for photoprotection. Our work thus demonstrates that mixotrophy under temperature controlled natural light can serve as the viable solution to improve biomass productivity of Synechococcus elongatus PCC 7942 and for commercial production of natural or engineered value added compounds from the system. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1182–1192, 2017     

南海北部海域Synechococcus和Prochlorococcus生长率和被摄食消亡率——变化范围及其与环境因子的关系

2004年首次在南海北部海域使用选择性代谢抑制剂技术进行了Synechococcus和Prochlorococcus生长率和被摄食消亡率的研究.研究结果表明,ynechococcus高丰度值出现在次表层（15 m或20m）,位于温跃层之上,高生长率往往出现在丰度最大值水层上方;Prochlorococcus丰度在夏季出现次表层最大值,与温跃层深度基本一致,表层生长率高于真光层底部.Synechococcus真光层平均生长率为0.11～1.18 d^-1,被摄食消亡率为0.11～0.76 d^-1,分布格局均为从沿岸向外海方向升高.Prochlorococcus真光层平均生长率为0.23～0.49 d^-1,存在较明显的季节变化,夏季近岸略高于外海,而冬季的趋势正好相反;真光层平均被摄食消亡率为0.12～0.33 d^-1,冬夏两季均是近岸高于外海。温度、营养盐和光是影响Synechococcus生长率变化的重要因子.Synechococcus和Prochlorococcus丰度与群落生长率之间不存在相关关系,而与被摄食消亡率之间则存在显著的指数相关.根据Synechococcus和Prochlorococcus的生长率估算了它们的生产力及其对Pico-生产力的贡献.     

Phylogenetic diversity of Synechococcus strains isolated from the East China Sea and the East Sea

Phylogenetic relationships among 33 Synechococcus strains isolated from the East China Sea (ECS) and the East Sea (ES) were studied based on 16S rRNA gene sequences and 16S–23S rRNA gene internal transcribed spacer (ITS) sequences. Pigment patterns of the culture strains were also examined. Based on 16S rRNA gene and ITS sequence phylogenies, the Synechococcus isolates were clustered into 10 clades, among which eight were previously identified and two were novel. Half of the culture strains belonged to clade V or VI. All strains that clustered into novel clades exhibited both phycoerythrobilin and phycourobilin. Interestingly, the pigment compositions of isolates belonging to clades V and VI differed from those reported for other oceanic regions. None of the isolates in clade V showed phycourobilin, whereas strains in clade VI exhibited both phycourobilin and phycoerythrobilin, which is in contrast to previous studies. The presence of novel lineages and the different pigment patterns in the ECS and the ES suggests the possibility that some Synechococcus lineages are distributed only in geographically restricted areas and have evolved in these regions. Therefore, further elucidation of the physiological, ecological, and genetic characteristics of the diverse Synechococcus strains is required to understand their spatial and geographical distribution.     

Immunocytochemical localization of IdiA, a protein expressed under iron or manganese limitation in the mesophilic cyanobacterium Synechococcus PCC 6301 and the thermophilic cyanobacterium Synechococcus elongatus

Iron-deficiency-induced protein A (IdiA) with a calculated molecular mass of 35 kDa has previously been shown to be essential under manganese- and iron-limiting conditions in the cyanobacteria Synechococcus PCC 6301 and PCC 7942. Studies of mutants indicated that in the absence of IdiA mainly photosystem II becomes damaged, suggesting that the major function of IdiA is in Mn and not Fe metabolism (Michel et al. 1996, Microbiology 142: 2635–2645). To further elucidate the function of IdiA, the immunocytochemical localization of IdiA in the cell was examined. These investigations provided evidence that under mild Fe deficiency IdiA is intracellularly localized and is mainly associated with the thylakoid membrane in Synechococcus PCC 6301. The protein became distributed throughout the cell under severe Fe limitation when substantial morphological changes had already occurred. For additional verification of a preferential thylakoid membrane association of IdiA, these investigations were extended to the thermophilic Synechococcus elongatus. In this cyanobacterium Mn deficiency could be obtained more rapidly than in the mesophilic Synechococcus PCC 6301 and PCC 7942, and the thylakoid membrane structure proved to be more stable under limiting growth conditions. The immunocytochemical investigations with this cyanobacterium clearly supported a thylakoid membrane association of IdiA. In addition, evidence was obtained for a localization of IdiA on the cytoplasmic side of the thylakoid membrane. All available data support a function of IdiA as an Mn-binding protein that facilitates transport of Mn via the thylakoid membrane into the lumen to provide photosystem II with Mn. A possible explanation for the observation that IdiA was not only expressed under Mn deficiency but also under Fe deficiency is given in the discussion. Received: 28 July 1997 / Accepted: 26 November 1997     

Growth and removal of nitrogen and phosphorus by free-living and chitosan-immobilized cells of the marine cyanobacterium Synechococcus elongatus

This study investigated the growth rate of chitosan-immobilized cells of the marine cyanobacterium Synechococcus elongatus and its potential application in the removal of nitrogen and phosphorus for wastewater treatment. Immobilized cell cultures had a lag phase of growth due to the immobilization method, and their growth rate was similar to that of free-living cell cultures. Ammonia removal was higher in free cells (54%) than in immobilized cells (29%), but nitrate removal was similar in immobilized (38%) and free cells (44%); phosphorus removal was more efficient in free cells (88%) than in immobilized cells (77%). Chlorophyll a and protein content were higher in immobilized cells. Our study demonstrates that S. elongatus immobilized into chitosan capsules can remove nutrients and is able to maintain a growth rate comparable to that of free cells in culture.     

聚球藻Synechococcus sp.PCC7942高CO_2需求突变株的筛选及其超微结构观察(英文)

以单细胞蓝藻聚球藻Synechococcussp.PCC7942为材料,利用甲基磺酸乙酯(EMS)进行化学诱变获得了一个高CO2 需求突变株。它能在 4%CO2 下生长而不能在空气中生长。对突变株的初检表明:其回复突变率约为 10 -7。该突变株从高CO2 条件下转到空气中后,细胞在 2～ 3d内逐渐趋于死亡;其光合作用对外源无机碳的依赖性高于野生型细胞,碳酸酐酶活性也低于野生型细胞。在超微结构水平,突变株细胞内出现了不同类型的异常羧体:有的为棒状;有的为不规则状;有的为 空羧体",而且,类囊体周围糖原颗粒增多。进一步说明该突变株在CO2 吸收和利用功能上有缺陷。此外,对低碳条件对羧体的诱导及羧体的生物发生也作了一些探讨     

聚球藻7002嗜铁素的检测与分离

【目的】探究聚球藻7002嗜铁素的检测和分离方法,为深入研究海洋嗜铁素提供科学依据。【方法】在缺铁MediumA中培养聚球藻7002,利用双层平板法、混合平板法和传统铬天青S(CAS)平板法定性检测嗜铁素,用CAS蓝色液体检测液定量检测嗜铁素。采用大孔树脂XAD-2和固定化金属离子亲和层析(IMAC)对嗜铁素进行分离,IMAC采用降低pH和竞争性洗脱两种洗脱方式。【结果】混合平板定性检测法更快速、高效、便捷。缺铁培养的聚球藻7002发酵液中,嗜铁素的相对含量高达93.50%。大孔树脂分离,上样液pH调为2.0时,嗜铁素吸附充分,分离效果较好。试验发现,分离得到的聚球藻7002嗜铁素在254nm紫外下具有明显的荧光特性。【结论】试验得到了聚球藻7002嗜铁素定性检测和分离的有效方法。