An Enzymatic Conversion of Lipoxygenase Products by a Hydroperoxide Lyase in Blue-Green Algae (Oscillatoria sp.)

An enzyme has been isolated from blue-green algae Oscillatoria sp. which utilizes the product, 13-hydroperoxy-9, 11-octadecadienoic acid (13-HPOD), of lipoxygenase for its substrate. This enzyme, termed hydroperoxide lyase, converts the conjugated diene 13-hydroperoxide of linoleic acid to 13-oxotrideca-9, 11-dienoic acid. The structure of the latter has been determined by ultraviolet spectroscopy and mass spectrometry. 9-HPOD is not a substrate for this enzyme. The hydroperoxide lyase from Oscillatoria sp. has a maximum of activity at pH 6.4 and 30°C. The molecular weight of the enzyme was estimated at 56,000. The enzyme was not inhibited by BW 755C, but was inhibited by molecules containing more than one hydroxyl group. Quercetin was found to be the best inhibitor of the enzyme activity. The purified hydroperoxide lyase from Oscillatoria sp. showed an apparent K_m of 7.4 micromolar and a V_max of 35 nanomoles per minute per milligram of protein for 13-HPOD. An enzymatic pathway for the biogenesis of oxodienoic acid from linoleic acid is proposed. This involves the sequential activity of lipoxygenase and hydroperoxide lyase enzymes.     

刚毛藻在水螅培养中的应用

首次探索刚毛藻在水螅培养中的应用价值。实验每天投放过量水蚤喂水螅．连续42d不换水,发现刚毛藻对水中N、P有显著去除作用,并且在改善水质条件、抑制绿藻生长、稳定pH值和增加水体溶解氧等方面具有显著效果。该方法可为饲养者节约大量时间、人力和水资源。寒暑假期间,在室温5-28℃的无人培养条件下,能维持一定数量的水螅。     

Urceolaria viridis n. sp., a Ciliate (Peritrichida, Mobilina) with Elongate Symbiotic Green Algae

SYNOPSIS. A new peritrichous ciliate containing elongate symbiotic green algae is described from the marine limpet Acmaea digitalis Eschscholtz (1833). Urceolaria viridis n. sp. is characterized as follows: turban-shaped; diam. 40 μ; diam. striated band 30 μ; diam. corona 23 μ; width of corona 2μ; 16–22 denticles; peristome slightly more than one turn; circlet of delicate cirri adoral to ciliary girdle; macronucleus H-shaped with both ends of side pieces widely separated; diam. micronucleus 4.5 μ, endosome 2.5 μ; cytoplasm containing elongate green algae measuring 2–4 by 8–16 μ.     

Properties of a hyperthermophilic bacterium (Thermus sp.) isolated from a Carlsbad spring

A bacterial strain belonging to the speciesThermus was isolated from the water of a Carlsbad hot spring at 70–73°C. The microorganism can grow aerobically and forms yellow and orange colonies on a special medium, due to a carotenoid pigment. The growth optimum is 70–75°C. The minimum and maximum temperatures for growth are 40 and 80°C, respectively. The microorganism is a Gram-negative, rod-like, immobile bacterium, its characteristic feature being the ability to form long filaments (up to 200 μm long). The content of guanine and cytosine in DNA is 65.1 %. This rare endemic microorganism was isolated and described in detail in Czechoslovakia for the first time. It was included in theCzechoslovak Collection of Microorganisms of the Masaryk University in Brno and is available under the catalog number of CCM 4167. Translated by Č. Novotny     

Dynamic Mechanical Properties of the Cell Walls of Some Green Algae

Stress relaxation and constant rate of strain measurements weremade on the cell walls of the green algae Nitella, Acetabularia,and Penicillus. These plants have, as theirmain structural polysaccharide,cellulose, mannan, and xylan respectively. The stress relaxationmeasurements were made in the temperature range 0 to 50 °Cfor the interval 0.02 to 10³ s. A limited number of constantrate of strain curves were also obtained for comparison withtheoretical curves deduced from the relaxation data. All three algae exhibit typical fibrous behaviour but Acetabulariacould not be mechanically conditioned to give reproducible results.The time-temperature correspondence of the data and its relevanceto the molecular organization of the cell wall are discussed.Structural changes with temperature, deduced in previous workfrom rigorous matching of the relaxation curves at differenttemperatures, are now thought not to occur. The matching procedureonly appears to work because the curves lack distinctive featureson which to base the superposition. Comparison of stress relaxationand constant rate of strain data show that the cell walls ofthese algae exhibit non-linear viscoelastic behaviour and apparentchanges in the quasi-static modulus with temperature can beexplained satisfactorily in terms of reaction rate theoriesfor viscoelastic processes.     

On the Properties of the Starch Granules from Unicellular Green Algae

Starch granules from Chlorella, Chlamydomonas and Scenedesmus, grown heterotro-phically in a medium containing organic carbon sources, were isolated by means of the toluol treatment of the sonicate of alga. The toluol treatment separated the starch granules in the water layer from the cells and cell debris coagulated in the upper toluol layer.

The starch granules of Chlorella vulgaris and Chlamydomonas sp. were composed of amylose (12 to 3%) and amylopectin. The amylose content of the starch granules of Scenedesmus basilensis was 22 %. All the X-ray diffraction patterns of algal starch obtained in this investigation were of the A-type, identical to that of corn starch.     

Dark anaerobic nitrogen fixation (acetylene reduction) in the cyanobacterium Oscillatoria sp.

The filamentous, non-heterocytous, nitrogen-fixing cyanobacterium Oscillatoria sp. strain 23 (Oldenburg) showed cycling of acetylene reduction in light-dark cycles. Under aerobic conditions nitrogenase activity is exclusively present during the dark period. However, if anaerobic conditions were applied during the dark period, two activity maxima were observed. A relatively small activity peak occurred during the first few hours of the dark period and a high peak as soon as the light was switched on. A low activity remained during the second half of the dark period. This pattern of acetylene reduction in Oscillatoria agrees well with the field data on nitrogen fixation [Stal, L.J. and Krumbein, W.E. (1984), Mar. Biol. 82, 217–224].     

USF-19A,a New Lipoxygenase Inhibitor from Streptomyces sp.

USF-19A, a soybean Jipoxygenase (SBL) and human 5-lipoxygenase (5-LO) inhibitor, was isolated from Streptomyces sp. USF-19 strain. Its chemical structure was determined by spectroscopic evidence to be a new member of the antimycin antibiotic family. The IC₅₀ value of USF-19A against 5-LO was 28.0 μM.     

Rhodopsin Receptors of Phototaxis in Green Flagellate Algae

Green flagellate algae are capable of the active adjustment of their swimming path according to the light direction (phototaxis). This direction is detected by a special photoreceptor apparatus consisting of the photoreceptor membrane and eyespot. Receptor photoexcitation in green flagellates triggers a cascade of rapid electrical events in the cell membrane which plays a crucial role in the signal transduction chain of phototaxis and the photophobic response. The photoreceptor current is the earliest so far detectable process in this cascade. Measurement of the photoreceptor current is at present the most suitable approach to investigation of the photoreceptor pigment in green flagellate algae, since a low receptor concentration in the cell makes application of optical and biochemical methods so far impossible. A set of physiological evidences shows that the phototaxis receptor in green flagellate algae is a unique rhodopsin-type protein. It shares common chromophore properties with retinal proteins from archaea. However, the involvement of photoelectric processes in the signal transduction chain relates it to animal visual rhodopsins. The presence of some enzymatic components of the animal visual cascade in isolated eyespot preparations might also point to this relation. A retinal-binding protein has been identified in such preparations, the amino acid sequence of which shows a certain homology to sequences of animal visual rhodopsins. However, potential function of this protein as the phototaxis receptor has been questioned in recent time.     

淡水球状绿藻一新种——汾河麦可藻

麦可属(Mychonastes)是一种分布广泛的超微型球状绿藻,是微藻能源生产、水质净化方面的潜力藻种。该研究对采自山西省太原市汾河公园的水样分离得到的一株球状绿藻(FHGY-19)进行藻株形态显微观察,并进行18S rDNA系统发育与ITS2二级结构分析鉴定,以明确FHGY-19的分类位置以及生态利用潜力。结果表明:(1)FHGY-19藻株为单细胞,球形,直径1.5~2.5μm,无黏质被膜,杯状叶绿体1个,周生,不具蛋白核,以2~4个似亲孢子进行繁殖,常见2个似亲孢子包被于母细胞壁内。(2)18S rDNA系统发育分析表明,藻株FHGY-19位于麦可属分支内部,与麦可属内的其他成员共同形成环藻目内一独立的单系分支,且FHGY-19与麦可属分支中的Mychonastes sp.5C3和Mychonastes sp.2C1亲缘关系较近,表明藻株FHGY-19为麦可属一成员。(3)ITS2 rDNA系统发育分析表明,FHGY-19与同是单细胞类型的Mychonastes frigidus、同球麦可藻(M.homosphaera)、M.pusillus、M.rotundus和M.ovahimbae聚为一支,且FHGY-19与5个藻种在ITS2二级结构上的总CBCs(碱基补偿替换)和保守区域HelixⅢ上的CBCs数分别为16个/7个、13个/6个、12个/4个、11个/4个和14个/5个,但藻株FHGY-19与系统发育树另一支的6个物种在ITS2序列长度、二级结构中总CBCs及HelixⅢ上的CBCs数均不同,表明FHGY-19的ITS2二级结构不同于已描述的11个种,为麦可属一新种。研究鉴定确认FHGY-19藻株为麦可属一新种,命名为汾河麦可藻(Mychonastes fenhensis sp.nov.)。FHGY-19藻株保存于太原师范学院淡水藻种库。     

Carbon Concentration Mechanism(s) in Unicellular Green Algae and Cyanobacteria

Unicellular green algae and cyanobacteria have mechanism(s) to actively concentrate dissolved inorganic carbon (DIC) into the cells, only if they are grown with air levels of CO₂. The DIC concentration mechanisms are environmental adaptations to actively transport and accumulate inorganic carbon into the chloroplasts of green algae or into the carboxysomes of cyanobacteria. The current working model of cyanobacterial carbon concentration mechanism consists of at least two basic components: an active C_i transport system and a Rubisco-rich polyhedral carboxysome. In case of unicellular green algae, the working model for DIC concentration mechanism includes several isoforms of carbonic anhydrase (CA), and ATPase driven active bicarbonate transporters at the plasmalemma and at the inner chloroplast envelopes. In the past twenty years, significant progress has been made in isolating and characterizing the isoforms of carbonic anhydrase. However, active transporters are yet to be characterized. This mini-review summarizes the current status of research on DIC-pumps including its significance and possible application to increase the productivity of plants of economic importance.     

Primary hepatic neuroendocrine carcinoma in a baboon (Papio sp.)

Background  Primary neuroendocrine carcinomas of the liver have rarely been reported in humans and domestic animals, but not in non-human primates.
Methods  We describe the morphologic and immunohistochemical features of a primary hepatic neuroendocrine carcinoma found in a 29-year-old female baboon.
Results and conclusions  The neoplasm was characterized by multiple solid nodules that were multifocally distributed in the liver. Metastases were not observed. Histologically, the neoplasm was composed of cords and nests of epithelial cells arranged in a neuroendocrine pattern, occasionally forming glandular and rosette-like structures. On immunohistochemical evaluation, the neoplastic cells were immunopositive for pancytokeratin, chromogranin A, neuron-specific endolase, and synaptophysin and were negative for vimentin, S100 protein, glucagon, and insulin.