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排序方式: 共有419条查询结果,搜索用时 125 毫秒
51.
Eliška Zapomělová Jitka Jezberová Pavel Hrouzek Daniel Hisem Klára Řeháková Jaroslava Komárková 《Journal of phycology》2009,45(6):1363-1373
Occurrences of rare cyanobacteria Anabaena reniformis Lemmerm. and Aphanizomenon aphanizomenoides (Forti) Horecká et Komárek were recently detected at several localities in the Czech Republic. Two monoclonal strains of An. reniformis and one strain of Aph. aphanizomenoides were isolated from distant localities and different sampling years. They were characterized by a combination of morphological, genetic, and biochemical approaches. For the first time, partial 16S rRNA gene sequences were obtained for these morphospecies. Based on this gene, all of these strains clustered separately from other planktonic Anabaena and Aphanizomenon strains. They appeared in a cluster with Cylindrospermopsis Seenaya et Subba Raju and Raphidiopsis F. E. Fritsch et M. F. Rich, clustered closely together with two An. kisseleviana Elenkin strains available from GenBank. A new generic entity was defined (Sphaerospermum gen. nov., with the type species S. reniforme, based on the traditional species An. reniformis). These results contribute significantly to the knowledge base about genetic heterogeneity among planktonic Anabaena–like and Aphanizomenon–like morphospecies. Accordingly, the subgenus Dolichospermum, previously proposed for the group of planktonic Anabaena, should be revaluated. Secondary metabolite profiles of the An. reniformis and Aph. aphanizomenoides strains differed considerably from 17 other planktonic Anabaena strains of eight morphospecies isolated from Czech water bodies. Production of puwainaphycin A was found in both of the An. reniformis strains. Despite the relatively short phylogenetic distance from Cylidrospermopsis, the production of cylindrospermopsin was not detected in any of our strains. 相似文献
52.
SHI Ding-Ji YE Xin ZHONG Hui CAI Yi-Ying SHAO Ning PENG Guo-Hong DONG Xiao-Jun WANG Chun-Mei OUYANG Ye-Xin LI Zhen-Jia 《植物学报(英文版)》2001,43(1):46-50
The effects of N (NaNO3) and C (NaAc) source in medium on the expression of tumor necrosis factor-α (TNF-α) gene in transgenic Anabaena sp. PCC 7120 were compared. The data showed that N source stabilized the expression of foreign protein and C source altered the synthesis of cell walls. Comparing several methods for breaking the cells, supersonic was able to extract TNF-α better than others. For purification of TNF-α, transgenic Anabaena cells were broken, the extracts were precipitated with ammonia sulfate, and the impure TNF-α was eluted from DEAE ion exchange chromatography. Electrophoresis (PAGE-SDS) showed a single band at 17 kD position. 相似文献
53.
在28℃下,采用群体累积培养法,探讨了不同浓度的蛋白核小球藻(Chlorella pyrenodeosa)、水华鱼腥藻(Anabaena flas-aquae)和沙角衣藻(Chlamyclomoras sajao),以及在等生物量条件下,以上3种藻类两两配比饵料(3:1、1:1和1:3)对萼花臂尾轮虫(Brachionus calyciflorus)的培养效果。结果表明,不同浓度的蛋白核小球藻、水华鱼腥藻和沙角衣藻对萼花臂尾轮虫增殖效果的影响分别表现为差异极显著(P〈0.01)、显著(P〈0.05)和不显著(P〉0.05);蛋白核小球藻与水华鱼腥藻组成的混合饵料对萼花臂尾轮虫的增殖效果均优于其中的单一种类(P〈0.05);沙角衣藻无论是单独投喂,还是与其它藻类混合投喂,轮虫的培养效果均不理想。因此,该种类不宜用作轮虫饵料开发。该研究还表明,蛋白核小球藻是培养萼花臂尾轮虫的最适单一种类,它与水华鱼腥藻组成的混合饵料培养萼花臂尾轮虫效果更好。 相似文献
54.
【目的】表达鱼腥藻苯丙氨酸脱氨酶(AvPAL),并经分子改造降低其最适反应pH。【方法】PCR克隆AvPAL编码基因,并在大肠杆菌中表达,用Ni2+亲和层析柱和凝胶柱纯化重组蛋白。利用GETAREA软件筛选与催化残基距离较近的暴露于酶分子表面的氨基酸位点,将其突变为带电性质不同的氨基酸,并对突变体进行酶学性质研究。【结果】在大肠杆菌中成功表达了AvPAL,纯化后得到电泳纯的重组酶。突变体E75Q和E75R的最适反应pH从8.5分别偏移到7.5和7.0。E75Q在pH 7.5时的比酶活较原酶提高了25%,在pH 6.5–9.5之间酶的稳定性良好,其最适反应温度为50 °C,在此温度下保温1 h酶活无显著变化。在最适反应条件下,E75Q的kcat/Km值较原酶提高了26.6%。【结论】改变AvPAL酶分子中起路易斯碱作用的关键氨基酸残基(质子受体)附近与之有相互作用的氨基酸的带电性质,降低了AvPAL的最适反应pH,提升了其在医疗领域的应用前景。 相似文献
55.
56.
H. Mobasheri T.A. Ficht H. Marquis E.J.A. Lea J.H. Lakey 《FEMS microbiology letters》1997,155(1):23-30
Brucella usually carry two highly homologous genes (omp2a and omp2b) for porin-like proteins. In several B. abortus biovars the omp2a gene has a large deletion compared to other Brucella omp2's. In this study we have measured Omp2 pore activity in planar bilayers. Omp2b exhibits well-defined trimeric channel activity whilst Omp2a forms monomeric pores of variable size which are smaller than Omp2b. No sequence homology exists between Omp2 and porins of known structure, so hydrophobic moment analysis has been used to model their membrane topology. From this it appears likely that the deletion removes the crucial L3 internal loop. 相似文献
57.
The free-living cyanobacterium Anabaena variabilis showed a biphasic pattern of 14CH3NH
3
+
uptake. Initial accumulation (up to 60 s) was independent of CH3NH
3
+
metabolism, but long-term uptake was dependent on its metabolism via glutamine synthetase (GS). The CH3NH
3
+
was converted into methylglutamine which was not further metabolised. The addition of l-methionine-dl-sulphoximine (MSX), to inhibit GS, inhibited CH3NH
3
+
metabolism, but did not affect the CH3NH
3
+
transport system.NH
4
+
, when added after the addition of 14CH3NH
3
+
, caused the efflux of free CH3NH
3
+
; when added before 14CH3NH
3
+
, NH
4
+
inhibited its uptake indicating that both NH
4
+
and CH3NH
3
+
share a common transport system. Carbonylcyanide m-chlorophenylhydrazone and triphenyl-methylphosphonium both inhibited CH3NH
3
+
accumulation indicating that the transport system was -dependent. At pH 7 and at an external CH3NH
3
+
concentration of 30 mol dm-3, A. variabilis showed a 40-fold intracellular accumulation of CH3NH
3
+
(internal concentration 1.4 mmol dm-3). Packets of the symbiotic cyanobacterium Anabaena azollae, directly isolated from the water fern Azolla caroliniana, also showed a -dependent NH
4
+
transport system suggesting that the reduced inhibitory effect of NH
4
+
on nitrogenase cannot be attributed to the absence of an NH
4
+
transport system but is probably related to the reduced GS activity of the cyanobiont.Abbreviations CCCP
carbonylcyanide m-chlorophenylhydrazone
- GS
glutamine synthetase
- HEPES
4-(2-hydroxyethyl)-1-piperazine ethanesulphonic acid
- MSX
l-methionine-dl-sulphoximine
-
membrane potential
- pH
transmembrane pH difference
- TPMP+
triphenylmethylphosphonium 相似文献
58.
59.
60.
鱼腥藻1017株的混合营养型生长 总被引:8,自引:1,他引:8
鱼腥藻1017株混合营养型生长有其特点,外源葡萄糖对生长的刺激不仅在低光强(800lx),而且在高光强(7000lx)也表现出来。其混合营养型生长速率在800-7000lx范围内随光照强度的增加而增加,在葡萄糖浓度5-20mmol/L范围内随外源葡萄糖浓度增加而增加。鱼腥藻1017株混合营养型生长与光能自养生长相比,生长速率明显提高,对数生长期延长,收获物浓度显著增高,生物量显著提高。 相似文献