中国淡水水体常见束丝藻种类的形态及生理特性研究

束丝藻(Aphanizomenon Morr. ex Born. et Flah)是我国水华蓝藻的重要种类, 由其产生的束丝藻水华已经引起了许多的环境问题。水华束丝藻、柔细束丝藻和依沙束丝藻是我国淡水水体常见的三种束丝藻种类,然而, 国内外对它们的生理学研究却相对较少。基此, 文章对水华束丝藻、柔细束丝藻和依沙束丝藻的形态特性、色素含量、生长及光合作用进行了比较研究, 结果表明丝状体的营养细胞、异形胞和厚壁孢子的长宽比具有一定的差异性, 揭示了厚壁孢子的长宽比可作为三种束丝藻分类的一个参数; 同时, 种间的差异性也体现在三种束丝藻的生理特性上, 相比水华束丝藻和依沙束丝藻, 柔细束丝藻的藻蓝素含量较高, 而叶绿素a、类胡萝卜素含量、最大光合作用(Pm)、表观光合作用效率(α)和最大电子传递速率(ETRmax)显著偏低。此外, 水华束丝藻和依沙束丝藻生理特性基本一致, 表明了形态不同的三种束丝藻在生理上可被分为两种类型, 暗示了依沙束丝藻可能具有像水华束丝藻一样形成水华的生理潜能且由于它的产毒性所以应该倍加关注       

共球藻纲丝状藻中国新记录属种——洪泛拟寇丽藻

从甘肃省张掖市黑河流域分离了一株不分枝的丝状绿藻,对其进行纯培养并保藏于中国科学院淡水藻种库,编号FACHB 2451。形态观察表明,该藻株具有相对较长的营养细胞 (细胞长为宽的3~8倍)、双叶形的片状叶绿体、末端细胞顶端钝圆或略尖细等特征。结合形态比较和基于18S rDNA 基因序列的系统发育分析,确定该藻株为中国淡水共球藻纲新记录属种——洪泛拟寇丽藻 (Koliellopsis inundata Lokhorst)。分子系统发育研究结果表明,所分离的藻株与分离自比利时与荷兰边境农地的洪泛拟寇丽藻模式藻株序列相似度极高,且拟寇丽藻属与寇丽藻属、针丝藻属和拟针丝藻属等不分枝丝状拟寇丽藻科成员亲缘关系密切,可以较好地聚成一个亚支。     

洱海的浮游蓝藻布氏常丝藻及其分类学的讨论

常丝藻(Tychonema)是1988年由Anagnostidis和Komárek从颤藻属分离出来而新成立的蓝藻属,以纤细常丝藻(T.tenue)为模式种类。目前确认的常丝藻有纤细常丝藻、博多常丝藻(T.bornetii)和布氏常丝藻(T.bourrellyi)三个种类。我国已经有博多常丝藻的纪录,但是对模式种纤细常丝藻和它的相似种类布氏常丝藻却没有报道。在洱海中采集到布氏常丝藻(T.bourrellyi),研究并描述了该藻的藻丝颜色、藻细胞内含物的结构、藻体形态特征等。同时,通过藻种的分离培养技术,得到了布氏常丝藻的纯培养藻株,编号为CHAB663,并且测定了藻株的16S rRNA基因序列。测序结果表明,该藻株与T.bouurrellyi/T.tenue聚为一族。洱海分布的布氏常丝藻,是在欧洲以外首次发现此种藻类,也是我国的新纪录种。研究说明布氏常丝藻不仅仅分布在温带欧洲较为寒冷的水体中,在亚热带的水体中也可以存在。布氏常丝藻被认为是出现在轻微富营养化湖泊中,而我国洱海也被认为是富营养化的初级阶段的水体,这也表明,布氏常丝藻的出现对洱海的水环境状况起到了指示作用。此外,研究还对常丝藻属分类学问题进行了讨论。     

水华束丝藻对磷的生理响应研究

束丝藻(Aphanizomenon Morr. ex Born. et Flah.)是我国淡水水体常见的水华蓝藻之一, 由其引发的水华已产生了严重的环境及生态安全问题。然而, 目前对束丝藻的研究仍相对较少。为了揭示环境因子对束丝藻的影响, 研究从淡水水体限制因子?磷入手, 探讨其对束丝藻的生理生态效应, 研究了不同磷浓度(0.00、0.02、0.05、0.50、1.00 mg/L)对水华束丝藻的生长、光合作用及碱性磷酸酶变化的影响。结果表明: 水华束丝藻在磷浓度低于0.50 mg/L 条件下, 其比生长速率()、最大光合反应(Pm)、饱和光强(Ik)、PSⅡ光化学效率(Fv/Fm)和最大电子传递速率(ETRmax)均下降, 而暗呼吸(Rd)显著增加, 这表明培养基磷浓度低于0.50 mg/L 时,水华束丝藻产生磷营养胁迫, 导致其光合作用受到抑制, 呼吸作用增强, 进而抑制其生长。为了应对这种胁迫, 束丝藻显著增加了其碱性磷酸酶活性(APA), APA 的增加, 使得水华束丝藻能够分解有机形态磷物质转化为其可利用无机磷来缓解磷胁迫。当磷浓度高于0.50 mg/L 时, 水华束丝藻各种参数并没显著性差异, 表明磷浓度高于0.50 mg/L 能够保证水华束丝藻的正常生理特征。这些结果揭示了在低磷条件下, 水华束丝藻能通过调节光合作用和APA 等生理响应, 使其保持生存和竞争优势。       

中国串珠藻属(红藻门)的两个新种

本文纪录了淡水红藻串珠藻属Batrachospermum的二个新种。它们采自中国的亚热地区,按其形态特征,它们属于旋转组Section Contorta。采自湖北省的弯形中珠藻B.curvatum与扭曲串珠藻B.tortuosum Kumano相似,但按其轮节、顶毛和受精丝等的形态与后者相区别。采自江西省的弯转串珠藻B.torsivum与赫罗西串珠藻B.hirosei Ratnasabapathy et Kumano相似,但轮节、中轴细胞、节丝和节间丝、果胞枝和受精丝等的大小和形态与后者相区别。     

洱海鱼腥藻优势种的形态鉴定与16S rRNA 基因序列分析

分别在2004年、2005年和2006年洱海鱼腥藻水华暴发时期,分离优势种,获得藻株EH-A、EH-B和EH-C,通过形态学特征和16S rRNA基因序列分析鉴定了藻株的种类.选用藻丝的形态、气囊的存在与否、异形胞和孢子的位置、各种细胞的形状以及营养细胞、异形胞和孢子的大小等传统的分类特征描述藻株的形态.依据形态特征,初步判断这3个藻株可能为卷曲鱼腥藻(Anabaena circinalis)或 A.crassa株系成员.利用16S rRNA基因序列构建邻接树分析了藻株间的系统进化关系,分析表明:藻株EH-A、EH-B和EH-C序列的同源性达到100%,且与A.circicular 和A.crassa藻株组成一个群(cluster),其藻株间的序列相似度高达100%,进一步说明藻株EH-A、EH-B和EH-C为相同的物种,且均为卷曲鱼腥藻(A.circinalis)或A.crassa.     

中国淡水硅藻新记录——偏肿内丝藻兴凯变种

于2016年5月对浙江省仙居国家公园进行藻类多样性调查时,发现了中国淡水硅藻的1个新记录种——偏肿内丝藻兴凯变种[Encyonema ventricosum var.hankensis(Skvortzov) RodionovaPomazkina]。该文采用光镜和扫描电镜对偏肿内丝藻兴凯变种浙江种群的形态特征进行了观察和描述,并将其与该种的其他地理种群及内丝藻属其他相似物种的形态特征进行比较,同时讨论了该物种的生境特征。结果表明:(1)偏肿内丝藻兴凯变种壳面均具明显背腹之分,背缘明显拱起,腹缘轻微波曲;端部呈头状至喙状。(2)偏肿内丝藻兴凯变种浙江地理种群在背部中央区域具一孤点,而其兴凯种群对孤点这一特征未有描述。(3)偏肿内丝藻兴凯变种在俄罗斯的兴凯湖和贝加尔湖等地有分布,该种在中国是首次报道。     

我国鱼腥藻的新记录种——粘质鱼腥藻

蓝藻是淡水水体的重要组成类群,而鱼腥藻又是水华蓝藻的一个重要种属.但由于该属种类较多,国内文献报导的不到世界分布的四分之一.该文利用染色和显微镜镜检方法对采自广东省高州水库蓝藻水华的样品进行观察,经鉴定,确认一个我国鱼腥藻属的新记录种--粘质鱼腥藻Anabaena mucosa, J. Komarkova-Legnerova & P. Eloranta ,1992 .对该属及该属一个新记录种的主要形态学特征进行了描述,提供了相应的形态照片,并对相似种进行了形态学比较研究.     

古尔班通古特沙漠生物结皮微鞘藻分类学研究

实验研究了从古尔班通古特沙漠生物土壤结皮中分离纯化培养出的11株与微鞘藻(Microcoleus)形态接近的丝状蓝藻,通过形态特征、16S rRNA和ITS二级结构相结合的多相分析方法对其进行分类学研究。研究结果表明,实验藻株隶属于微鞘藻科(Microcoleaceae)的微鞘藻属(Microcoleus)和束脉藻属(Symplocastrum),其中包括2个中国新记录种:斯坦微鞘藻(Microcoleus steenstrupii)和细长束脉藻(Symplocastrum flechtnerii),另外还有具鞘微鞘藻(Microcoleus vaginatus)和类似斯坦微鞘藻的存疑物种。藻丝多少与排列方式、细胞大小与末端细胞形状,以及16S rRNA系统发育位置是确定微鞘藻(Microcoleus)与束脉藻(Symplocastrum)属于不同物种的关键依据, ITS二级结构是区分属内不同物种的重要参考。     

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...     

Effect of canavanine and other amino acid analogues on akinete formation in the cyanobacterium Anabaena cylindrica

Addition of the arginine analogue, canavanine, to cultures of nitrogen-fixing Anabaena cylindrica at the onset of akinete formation, resulted in the development of akinetes randomly distributed within the filament, in addition to those adjacent to heterocysts. The total frequency of akinetes increased up to five-fold. A feature of akinetes is their increased content of cyanophycin granules (an arginine-aspartic acid polymer) and addition of canavanine to cultures at an earlier stage resulted in entire filaments becoming agranular and containing agranular akinetes. The effects on akinete pattern appeared to be specific for canavanine since other amino acid analogues, although increasing the frequency of akinetes (approximately two-fold), had no effect on their position relative to heterocysts. In ammonia-grown, stationary phase cultures of A. cylindrica, akinetes were observed adjacent to proheterocysts and in positions more than 20 cells from any heterocyst. These observations indicate that nitrogen fixation and heterocysts are not essential for akinete formation in A. cylindrica, although the availability of a source of fixed nitrogen does appear to be a requirement.These results suggest that during exponential growth some aspect of the physiology of vegetative cells suppresses their development into akinetes and that the role of the heterocyst may not be one of direct stimulation of adjacent vegetative cells to form akinetes, but the removal or negation of the inhibition within them. A model for akinete formation and the involvement of canavanine is given.     

DEVELOPMENT AND GERMINATION OF AKINETES OF APHANIZOMENON FLOS-AQUAE1

Flakes of Aphanizomenon flos-aquae collected from an ice-covered lake were found to contain all developmental stages from vegetative cells to mature akinetes. Changes during development include increase in cell size, gradual disappearance of gas vacuoles (clusters of gas vesicles), narrowing of intrathylakoidal spaces, and increase in cytoplasmic density. Development of akinetes is accompanied by proliferation of ribosomes, including polyribosomes, cyanophycin granules (structured, granules), and glycogen granules. The lipid bodies of vegetative cells are reduced in size and number in mature akinetes. Akinetes may occur singly or as multiples in sequence in a filament, either terminal or intercalary. Loss of flotation by increase in cytoplasmic density permits filaments to sink and overwinter in bottom sediments. The sequence was found to be reversed during germination of akinetes. Cyanophycin granules are reduced in size and staining density in the sporelings, and very few glycogen granules are seen. Gas vesicles reappear and increase in number, and intrathylakoidal spaces become wider. These changes then would permit the sporelings to rise from the bottom and begin another season's bloom.     

A new species of Anabaenopsis (A. venkataramanii sp. nov.) from India

Summary A new species of Anabaenopsis (A. venkataramanii sp. nov.) is reported from India.A detailed account for the morphology of this alga together with the origin and development of the akinetes and heterocysts is given. It is stressed that the peculiar development of the heterocysts is a more important taxonomic criterion for the genus rather than the presence or absence of terminal heterocysts.     

Cellular differentiation in the cyanobacterium Nostoc punctiforme

Nostoc punctiforme is a phenotypically complex, filamentous, nitrogen-fixing cyanobacterium, whose vegetative cells can mature in four developmental directions. The particular developmental direction is determined by environmental signals. The vegetative cell cycle is maintained when nutrients are sufficient. Limitation for combined nitrogen induces the terminal differentiation of heterocysts, cells specialized for nitrogen fixation in an oxic environment. A number of unique regulatory events and genes have been identified and integrated into a working model of heterocyst differentiation. Phosphate limitation induces the transient differentiation of akinetes, spore-like cells resistant to cold and desiccation. A variety of environmental changes, both positive and negative for growth, induce the transient differentiation of hormogonia, motile filaments that function in dispersal. Initiation of the differentiation of heterocysts, akinetes and hormogonia are hypothesized to depart from the vegetative cell cycle, following separate and distinct events. N. punctiforme also forms nitrogen-fixing symbiotic associations; its plant partners influence the differentiation and behavior of hormogonia and heterocysts. N. punctiforme is genetically tractable and its genome sequence is nearly complete. Thus, the regulatory circuits of three cellular differentiation events and symbiotic interactions of N. punctiforme can be experimentally analyzed by functional genomics.     

A CARD-FISH protocol for the identification and enumeration of cyanobacterial akinetes in lake sediments

Akinetes are the dormant cells of Nostocales (cyanobacteria) that enable the organisms to survive harsh environmental conditions while resting in bottom sediments. The germination of akinetes assists the dispersal and persistence of the species. The assessment of the akinete pool in lake sediments is essential to predict the bloom formation of the Nostocales population. We present here the implementation of an improved catalysed reporter deposition (CARD)-fluorescence in situ hybridization (FISH) protocol to assist the identification and quantification of akinetes in sediment samples. Several 16S rRNA gene oligonucleotide probes were evaluated for labelling akinetes of various species of Anabaena, Aphanizomenon and Cylindrospermopsis. Akinetes of all the taxa studied were successfully labelled and could be easily detected by their bright fluorescence signal. The probes' specificity was tested with 32 strains of different taxa. All six Cylindrospermopsis raciborskii strains were labelled with a specific probe for its 16S rRNA gene. A more general probe labelled 73% of the Anabaena and Aphanizomenon strains. The counting data of field samples obtained with CARD-FISH and the regular light microscopy approach did not differ significantly, confirming the suitability of both methods. The CARD-FISH approach was found to be less time-consuming because of better visibility of akinetes.     

AKINETE FORMATION IN PLANKTONIC ANABAENA SPP. (CYANOBACTEFUA) BY TREATMENT WITH LOW TEMPERATURE1

The effects of temperature, light intensity and nutrient depletion on akinete formation in seven strains of planktonic Anabaena spp.: A. mucosa TAC426; A. crassa TAC436; A. spiroides TAC443 and TAC444; A. flosaquae TAC446; and A. ucrainica TAC448 and TAC449 were examined. A Marked Pfft of temperature on akinete formation was observed at 40 μmol photons·m^?2·sec^?1 and nutrient-sufficient conditions. At 20° C, akinetes did not develop in A. mucosa TAC426, A. crassa TAC436, A. spiroides TAC443, A. flos-aquae TAC446, or A. ucrainica TAC449 but were formed at frequencies of a little over 11% (ratio of filaments with akinetes to total filaments) in A. spiroides TAC444 and A. ucrainica TAC448. None of the strains fmd akinetes or heterocysts at 30° C and 35° C. At lower temperature (10° C and 15° C), akinetes developed in all the strains at maximum frequencies of 13.4–77.4% during the late exponential phase or late exponential to stationary phases of growth. With only one exception, low light or nutrient deletion did not lead to the induction of akinete diferentiation at 20° C. Only akinete formation in A. flosaquae TAC446 was induced by nitrogen deletion with a frequency of 12.1%, similar to that induced by low temperature, but the initiation of akinete formation in the strain was delayed compared to treatment with low temperature. These results show that temperature was the most important environmental factor triggering akinete formation in these species. In A. crassa TAC436 and A. spiroides TAC443 and TAC444, akinetes developed during the late exponential growth phase even though heterocysts were formed at a 100% frequency (ratio of filaments with heterocysts to total filaments) throughout the entire growth phase. In A. mucosa TAC426, A. flos-aquae TAC446, and A. ucrainica TAC448 and TAC449, there was a positive correlation between heterocyst and akinete formation, suggesting that the presence of a heterocyst may play a role in akinete formation.     

A Light and Electron Microscopic Study of Anabaena volzii Lemm

Anabaena volzii Lemm. is a rare species of Cyanophyta. It possesses characteristics of prokary0tes. Young filaments of A. volzii consist of only vegetative cells. The filament leng- thens by the increase of its cell number owing to amitosis. A mature filament contains vegetative cells, heterocysts and akinetes; the latter two differentiate from the vegetative cells. Vegetative cells and heterocysts are short-cylindric shaped. An akinete in longitudinal sections of appear to be elliptical. Viewed with a transmission electron microscope, an electron-dense cell wall, plasmolemma, thylakoids (photosynthetic lamellae), nucleo-plasmic region and polyhedral bodies can be seen in the vegetative cell. The nucleo-plasmic region, which lacks a nuclear envelope, is surrounded or dissected, but often connected with the thylakoids. There are also some extremely electron-dense (if samples were post-fixed in osmic acid) cyanophycin granules in its cytoplasm. Heterocyst is larger than vegetative cells. Its remarkable features are a thick envelope, an electron-transparent cell wall and a distinctive plug-like body at both ends of the cell respectively. In the plug-like body is seen an irregular narrow channel. Somewhat dilated thylakoids in the heterocyst appear to be more winding and contorted (than those in vegetative cells), making a dedicate pattern. A long ellipticring-shaped membrane structure is formed in a heterocyst ,composed, of an electron-dense rod core surrounded by 14 concentric layers of lamellae. Akinete forms thick cell wall. A nucleo-plasmic region, fine and contorted thylakoids, many cyanophycin granules, and abundant ribosomes are found in akinetes.     

Superoxide dismutase in vegetative cells, heterocysts and akinetes of Anabaena cylindrica Lemm

Abstract: Superoxide dismutase (SOD) activity was assayed in vegetative cells, heterocysts and akinetes of Anabaena cylindrica Lemm. The iron-containing isoenzyme (Fe-SOD) was in all cases predominant over the manganese-containing isoenzyme (Mn-SOD). Differentiated cells maintained the same relative content of the two enzymes as in vegetative cells. However, heterocysts and akinetes contained only 20 and 35%, respectively, of the total SOD activity present in vegetative cells.
Both Mn-SOD and Fe-SOD activities increased in all types of cells isolated from A. cylindrica grown at high light intensity. The increase of SOD in heterocysts paralleled that of nitrogenase, suggesting a role of SOD in the protection mechanism of nitrogenase.     

A NUMERICAL TAXONOMIC STUDY OF NOSTOC AND ANABAENA1

Thirty characteristics of 14 Nostoc and 10 Anabaena species were analyzed from previously published data. Using standard numerical taxonomic methods, simple matching coefficients were calculated and a phenogram drawn. The analysis revealed that some of the central characteristics of Nostoc are: a punctiforme stage; motile reproductive stage; plant mass with a dull to shiny luster, non-veined surface, and nonfimbriate margin; some spherical vegetative cells; no cylindrical heterocysts; and some spherical, but no cylindrical akinetes. Some of the central characteristics of Anabaena that were revealed are: no punctiforme stage; a motile vegetative stage; plant mass with a shiny luster, veined surface, and fimbriate margin; no spherical vegetative cells; some cylindrical heterocysts; and some cylindrical, but no spherical, akinetes. In general, Anabaena has larger akinetes and vegetative cells than Nostoc. Based on 30 morphological characteristics and the clustering data of the phenogram, keys were constructed for the Nostoc and Anabaena species studied. The data clearly support two separate and distinct, though similar genera and, less sharply, the separation of the 24 species. The more useful characteristics for separation of the species are size and shape of akinetes, vegetative cells, and heterocysts; color and luster of plant mass; veined plant mass surface; margin fimbriate; and shape of plant mass in nature.     

Massive multiplication of genome and ribosomes in dormant cells (akinetes) of Aphanizomenon ovalisporum (Cyanobacteria)

Akinetes are dormancy cells commonly found among filamentous cyanobacteria, many of which are toxic and/or nuisance, bloom-forming species. Development of akinetes from vegetative cells is a process that involves morphological and biochemical modifications. Here, we applied a single-cell approach to quantify genome and ribosome content of akinetes and vegetative cells in Aphanizomenon ovalisporum (Cyanobacteria). Vegetative cells of A. ovalisporum were naturally polyploid and contained, on average, eight genome copies per cell. However, the chromosomal content of akinetes increased up to 450 copies, with an average value of 119 genome copies per akinete, 15-fold higher than that in vegetative cells. On the basis of fluorescence in situ hybridization, with a probe targeting 16S rRNA, and detection with confocal laser scanning microscopy, we conclude that ribosomes accumulated in akinetes to a higher level than that found in vegetative cells. We further present evidence that this massive accumulation of nucleic acids in akinetes is likely supported by phosphate supplied from inorganic polyphosphate bodies that were abundantly present in vegetative cells, but notably absent from akinetes. These results are interpreted in the context of cellular investments for proliferation following a long-term dormancy, as the high nucleic acid content would provide the basis for extended survival, rapid resumption of metabolic activity and cell division upon germination.