两株钝顶螺旋藻紫外诱变株的特征

采用紫外诱变的方法筛选获得了两株优良的稳定钝顶螺旋藻突变株M1-3和M5-1,与出发株相比,M5-1较粗大,M1-3较细,但长很长,藻体螺旋数超过40;两株突变株的生长速度和光合放氧速率均有显著提高;M1-3的藻蓝蛋白含量高于出发藻株20.2%;突变株的长碳连不饱和脂肪酸含量高于出发藻株,总脂中M1-3含花生四烯酸（20：4）4.93%、M5-1含EPA（20：5）2.49%。两株突变株对NH4^ 和Zn^2 的抗性也发生了改变。     

Cadmium biosorption on Spirulina platensis biomass

Dry biomass of Spirulina platensis re-hydrated for 48 h was employed as a biosorbent in tests of cadmium(II) removal from water. Various concentrations of biomass (from 1 to 4 g l⁻¹) and metal (from 100 to 800 mg l⁻¹) were tested. Low biomass levels (X_o  2 g l⁻¹) ensured metal removal up to 98% only at Cd₀= 100 and 200 mg l⁻¹, while X_o  2.0 g l⁻¹ were needed at Cd₀ = 400 mg l⁻¹ to achieve satisfactory results. Whereas X_o = 4.0 g l⁻¹ was effective to remove up to Cd₀ = 500 mg l⁻¹, a further increase in metal concentration (Cd₀ = 600 and 800 mg l⁻¹) led to progressive worsening of the system performance. At a given biomass levels, the kinetics of the process was better at low Cd²⁺ concentrations, while, raising the adsorbent level from 1.0 to 2.0 g l⁻¹ and then to 4.0 g l⁻¹, the rate constant of biosorption increased by about one order of magnitude in both cases and the adsorption capacity of the system progressively decreased from 357 to 149 mg g⁻¹.     

Isolation of Biopterin-α-glucoside from Spirulina (Arthrospira) platensis and Its Physiologic Function

A fluorescent substance was isolated from the cyanobacterium with a yield of 4.5 mg per 10 g of dried Spirulina (Arthrospira) platensis cells by gentle extraction and ethanol fractionation followed by column chromatography. The fluorescent substance, which has absorption maxima at 256 nm and 362 nm (pH 8.4), was identified as biopterin-α-glucoside by spectrophotometry and nuclear magnetic resonance spectroscopy. Biopterin-α-glucoside prevented decolorization of the photosynthetic pigments, chlorophyll a, phycocyanin, and carotenoids in photosynthetic vesicles of Spirulina platensis cells, by ultraviolet irradiation. Received June 23, 1998; accepted September 10, 1998.     

A new model of phycobilisome in Spirulina platensis

Phycobilisomes (PBS) were isolated from blue-green alga Spirulina platensis. Scanning tunneling microscope was used to investigate the three-dimensional structure of PBS deposited on freshly cleaved highly oriented py-rolytic graphite (HOPG) in ambient condition at room temperature. The results showed that the rods of PBS radiated from the core to different directions in the space other than arrayed in one plane, which was different from the typical hemi-discoidal model structure. The diameter of PBS was up to 70 nm, and the rod was approximately 50 nm in length. Similar results were observed in Langmuir-Blodgett (LB) film of PBS. The dissociated PBS could reaggregate into rod-like structures and easily form two-dimensional membrane while being absorbed on HOPG, however, no intact PBS was observed. The filling-space model structure of PBS in Spirulina platensis with STM from three-dimensional real space at nanometer scale was found, which showed that this new structural model of PBS surely exists in blue     

钝顶螺旋藻藻种的紫外诱变初步筛选

目的:初步筛选钝顶螺旋藻藻种。方法:结合自然分离筛选和紫外诱变育种两种方法。结果:得到4株钝顶螺旋藻突变株Z3、Z7、Z9和Z10。结论:与出发株(螺旋数一般5~7个)相比:藻丝长度均明显变长,螺旋数超过40个,形体较大,易于采收,且其藻胆蛋白含量高于出发藻株6.0%,生长速度较快,上浮性较好,值得进一步研究利用。     

钝顶螺旋藻表达载体p215 t-spp的构建及转化

用合适的限制性内切酶消化载体p215t,胶回收获得含有gfp基因及amp基因大片段.设计引物,采用PCR扩增无菌钝顶螺旋藻A9藻株的强启动子片段;在T4连接酶的作用下进行体外连接重组,构建了带有螺旋藻启动子和gfp报告基因的新型表达载体p215t-spp.将该载体转入钝顶螺旋藻,利用报告基因的表达,在荧光显微镜下观察并记录转化藻细胞,p215t-spp质粒显著提高转化率.研究了不同PEG浓度、转化时间及冰浴处理对转化率的影响.采用1%PEG能有效促进细胞吸收DNA,获得10.5‰的转化率.实验初步证明,带有螺旋藻启动子的报告基因gfp能够在钝顶螺旋藻中顺利表达.     

cpcHID操纵子序列用于钝顶节旋藻品系分类与鉴定的研究

克隆并测定7株钝顶节旋藻品系的cpcHID操纵子序列,以及16SrRNA和16S-23SrRNA转录单元内间隔区(ITS)序列,进一步通过生物信息学和分子系统学等研究发现:(1)7株品系的cpcHID序列,以及16SrRNA和ITS序列具有很高的相似性。(2)基于7株品系cpcHID序列的GC含量绝对偏差平均值、碱基变异率和遗传距离系数普遍比基于16SrRNA和ITS序列的大。(3)基于cpcHID序列的分类结果与基于16SrRNA和ITS序列的十分相近。因此,cpcHID可作为节旋藻等蓝细菌分类与鉴定的一种新的分子标记,特别是以其丰富的信息量而在品系水平的分类鉴定中占有优势。     

Growth characteristics of Arthrospira platensis cultured inside a new close-coil photobioreactor incorporating a mandrel to control culture temperature

The aim of this study was to investigate Arthrospira growth inside a new CCP incorporating a mandrel for culture temperature control. Some hydrodynamic aspects and photobioreactor performances were investigated as well. The bioreactor incorporated A. platensis grown under batch and semicontinuous conditions. Two systems were used to recycle Arthrospira cultures: a peristaltic pump and an airlift system. When the pump recycled the culture, we achieved a very high Dean number (De=3,950), which decreased a great deal when the pump was replaced with the airlift system. During outdoor Arthrospira batch growth, a cell concentration of 16.4 g (DW)l-1 was reached after 9 days. However, the maximum chlorophyll content of the biomass (2.0% of DW) was achieved on the fifth and sixth days. The highest daily biomass output rate was obtained using the airlift system, when the CCP was operated under a semicontinuous regime: the gross output rate was 2.85+/-0.37 g (DW) l-1 d-1 and the net was 2.32+/-0.11 g (DW) l-1 d-1. The advantages of the airlift system may be due to the low concentration of oxygen built up inside Arthrospira culture and the lack of cell damage due to the pump system. Thus, oxygen and pump stress may have been avoided.     

Redox potential of cytochrome c550 in the cyanobacterium Thermosynechococcus elongates

Cytochrome c550 (cyt c550) from photosystem II (PSII) exists in the PSII-bound form but can be released from PSII by treatment with divalent cations or Tris, yielding the isolated form. We calculated heme redox potentials (Em) based on the crystal structures of cyt c550 by solving the Poisson-Boltzmann equation. In the isolated form, the calculated Em are -240 mV at pH 6.0 and -352 mV at pH 9.0. This pH-dependence is predominantly due to deprotonation of the heme-propionic group near Asn-49. In the PSII-bound form, the calculated E(m) was up-shifted by 160 mV versus the isolated form due to a conformational change of protein backbone, yielding Em=-84 mV.     

Isolation and characterization of a metronidazole tolerant mutant of the cyanobacterium Spirulina platensis exhibiting multiple stress tolerance

Mutant cells of Spirulina platensis isolated after chemical mutagenesis (NTG treatment) exhibited approximately three-fold higher tolerance to metronidazole and DCMU (3,4-dichlorophenyl-1, 1-dimethylurea) as compared with wild-type cells. At the same time, mutant cells exhibited a several-fold higher tolerance to supra-high irradiance (38 W/m2) than the wild-type, a further response involving Hill reaction activity in the mutant towards the supra-high irradiance mechanism which enabled the mutant cells to withstand the high light intensities. The metronidazole and DCMU tolerance in the mutant cells could not be obviously attributed to lower rates of growth and photosynthesis as suggested previously. A typical coiling pattern in the mutant cells might result in a reduction of exposed surface area, thereby restricting entry of the above toxins. The mutant strains exhibiting tolerance to multiple stresses are potentially useful for application under field conditions.