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61.
《Harmful algae》2015
Despite their potential impact on phytoplankton dynamics and biogeochemical cycles, biological associations between algae and bacteria are still poorly understood. The aim of the present work was to characterize the influence of bacteria on the growth and function of the dinoflagellate Alexandrium tamarense. Axenic microalgal cultures were inoculated with a microbial community and the resulting cultures were monitored over a 15-month period, in order to allow for the establishment of specific algal–bacterial associations. Algal cells maintained in these new mixed cultures first experienced a period of growth inhibition. After several months, algal growth and cell volume increased, and indicators of photosynthetic function also improved. Our results suggest that community assembly processes facilitated the development of mutualistic relationships between A. tamarense cells and bacteria. These interactions had beneficial effects on the alga that may be only partly explained by mixotrophy of A. tamarense cells. The potential role of organic exudates in the establishment of these algal–bacterial associations is discussed. The present results do not support a role for algal–bacterial interactions in dinoflagellate toxin synthesis. However, variations observed in the toxin profile of A. tamarense cells during culture experiments give new clues for the understanding of biosynthetic pathways of saxitoxin, a potent phycotoxin. 相似文献
62.
Zenon Trela Tadeusz Janas Stanistaw Witek Stanislaw Przestalski 《Physiologia plantarum》1990,78(1):57-60
Effects of amphiphilic derivatives of glycine esters of the general formula (CH3 )3 N+ CH2 COOCn H2n+1 Cl- (n = 10, 12, 14, 16) on membrane potential and conductance in internodal cells of the alga Nitellopsis obtusa were studied. The compounds decreased the potential difference between vacuole and external medium and increased the electric conductance. The effects depended on the length of the alkyl chain (n) and the concentration of these quaternary ammonium salts. Light-induced hyperpolarization was suppressed by the salts. We suggest that the ammonium salts inhibit the electrogenic proton pump in the plasmalemma and enhance the passive efflux of Cl- from the algal cell. 相似文献
63.
M. Schreiner M. Geisert M. Oed J. Arendes U. Güngerich H. -J. Breter K. Stüber D. Weinblume 《Journal of molecular evolution》1995,40(4):428-442
The marine green coccoidal alga Nanochlorum eukaryotum (N.e.) is of small size with an average diameter of 1.5 m. It is characterized by primitive-appearing biochemical and morphological properties, which are considerably different from those of other green algae. Thus, it has been proposed that N.e. may be an early developed algal form. To prove this hypothesis, DNA of N.e. was isolated by a phenol extraction procedure, and the chloroplast DNA separated by preparative CsCl density-gradient centrifugation. The kinetic complexity of the nuclear and of the chloroplast DNA was evaluated by reassociation kinetics to 3 × 107 by and 9 × 104 bp, respectively. Several chloroplast genes, including the rRNA genes, were cloned on distinct fragments. The order of the rRNA genes corresponds to the common prokaryotic pattern. The 16S rRNA gene comprises 1,548 bases and is separated from the 23S rRNA gene with its 2,920 bases by a short spacer of 460 bases, which also includes the tRNAIle and tRNAAla genes. The 5S rRNA gene has not been found; it must start further than 500 bases downstream from the 3-end of the 23S rRNA gene. From the chloroplast rRNA sequences, we have deduced secondary structures of the 16S and 23S rRNAs, which are in agreement with standard models. The rRNA sequences were aligned with corresponding chloroplast sequences; phylogenetic relationships were calculated by several methods. From these calculations, we conclude that N.e. is most closely related to Chlorella vulgaris. Therefore, N.e. does not represent an early developed algal species; the primitive-appearing morphological and biochemical characteristics of N.e. must rather be explained by secondary losses.
Correspondence to: D. Weinblum 相似文献
64.
《Harmful algae》2016
Over the past few decades, there has been an increased frequency and duration of cyanobacterial Harmful Algal Blooms (HABs) in freshwater systems globally. These can produce secondary metabolites called cyanotoxins, many of which are hepatotoxins, raising concerns about repeated exposure through ingestion of contaminated drinking water or food or through recreational activities such as bathing/swimming. An ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) multi-toxin method has been developed and validated for freshwater cyanotoxins; microcystins-LR, -YR, -RR, -LA, -LY and -LF, nodularin, cylindrospermopsin, anatoxin-a and the marine diatom toxin domoic acid. Separation was achieved in around 9 min and dual SPE was incorporated providing detection limits of between 0.3 and 5.6 ng/L of original sample. Intra- and inter-day precision analysis showed relative standard deviations (RSD) of 1.2–9.6% and 1.3–12.0% respectively. The method was applied to the analysis of aquatic samples (n = 206) from six European countries. The main class detected were the hepatotoxins; microcystin-YR (n = 22), cylindrospermopsin (n = 25), microcystin-RR (n = 17), microcystin-LR (n = 12), microcystin-LY (n = 1), microcystin-LF (n = 1) and nodularin (n = 5). For microcystins, the levels detected ranged from 0.001 to 1.51 μg/L, with two samples showing combined levels above the guideline set by the WHO of 1 μg/L for microcystin-LR. Several samples presented with multiple toxins indicating the potential for synergistic effects and possibly enhanced toxicity. This is the first published pan European survey of freshwater bodies for multiple biotoxins, including two identified for the first time; cylindrospermopsin in Ireland and nodularin in Germany, presenting further incentives for improved monitoring and development of strategies to mitigate human exposure. 相似文献
65.
The water prerequisites of two drought tolerant Oscillatoria type cyanobacteria and one green alga were estimated by their ability to accomplish photosynthesis (carbon dioxide fixation) at conditions of subsaturating water supply. Fixation was zero in desiccated samples. Equilibration with solely water-saturated air did not enable any photosynthesis. However, granted properties of the physical environment of the samples could re-establish photosynthesis activity. These properties were elected by chosing membrane filters with different water retention characteristics as supporting substrata for the test samples in the de-and rehydration steps. Rehydration enabled the recovery of photosynthesis of desiccated samples only on the filters with good water retention, the filters with bad water retention were found ineffective. The Oscillatoria strains showed photosynthesis instantaneously and revealed nearly 100% viability. In contrast, rewetted cells of the green alga showed only 35% viability and the recovery of photosynthesis occurred only after 5 h. These differences reflect the natural environmental conditions: cyanobacteria are the first colonizers in the barren sand, whereas green algae can only start to colonize after progressing improvement of the water retention properties brought about by the pioneering cyanobacteria. The results will be discussed in the light of different specific mechanisms available to organisms which endeavour osmotic and matric water stress.Abbreviations DCMU
3(3,4-dichlorophenyl)-1,1-dimethyl-urea
- DMF
dimethylformamide
- PFD
photon flux density
- TAPS
N-tris[hydroxymethyl]methyl-3-amino-propanesulfonic acid 相似文献
66.
This investigation was conducted to characterize the algal inhibitory material originally isolated by Proctor (1957b) from Chlamydomonas. Analysis of purified extracts demonstrated that the inhibitor was a mixture of fatty acids. The identity and relative percentages of most of the components of the mixture were determined by GLC analysis. There is evidence that unsaturated fatty acids were responsible for the majority of the toxicity. 相似文献
67.
Summary Recent evidence has shown that algal cells acquire different flagella and a heterogeneous basal apparatus through the prolonged development of these structures over more than one cell cycle. A system for numbering algal flagella and basal bodies, which is based on developmental studies, is discussed along with the various means by which the flagellar/basal body developmental cycle can be determined. We review the information now available on development of the separate components of the flagellar apparatus-this comes particulary from the Chlorophyta and the Chromophyta-and attempt to elucidate any information which may help in phylogenetic comparisons. New data is provided on developmental changes in the cartwheel part of the basal body and basal body-associated connecting fibrils in green algae.Abbreviations Bb
basal body
- d
right (dexter) root
- df
right fibrils connecting Bb triplets to microtubular and/or fibrous roots
- EM
electron microscopy
- F
flagellum
- IMF
immunofluorescence microscopy
- LM
light microscopy
- NBBC
nucleus-basal body connector
- s
left (sinister) root
- sf
3left fibrils connecting Bb triplets to microtubular and/or fibrous roots. See Nomenclature section of Introduction for the numbering of basal bodies and their flagella; the same numbers apply to Bb-associated d and s roots, and df and sf fibrils 相似文献
68.
Summary The cryptomonadPyrenomonas salina presumably has arisen from a symbiotic event involving a flagellated phagotrophic host cell and a photosynthetic eukaryote
as the symbiont. Correspondingly, in this unicellular alga there are four different genomes, e.g., the nuclear and the mitochondrial
genomes of the host cell as well as the plastid genome and the genome contained in the vestigial nucleus of the endocytobiont
(nucleomorph). To analyze the orgin of one of the symbiotic partners the small subunit rRNA gene sequence of the host cell
nucleus was determined, and a secondary structure model has been constructed. This sequence is compared to those of 40 other
eukaryotes. A phylogenetic tree constructed using the neighborliness method revealed a close relationship between the host
cell ofP. salina and the chlorophytes, whereas the rhodophytes diverge more deeply in the tree. 相似文献
69.
The natural food ofOreochromis niloticus in Lake Awasa was studied from the stomach contents of 10 fish measuring 18–32 cm (standard length) monthly from August 1984 to April 1986.Chroococcus, Oscillatoria andBotryococcus were found to be important food items in the diet. Animal foods were observed on rare occasions and these were mainly Rotifera. Blue-green algae as a group contribute about 28.1% of the ash free dry weight (AFDW) whereas diatoms and green algae (excludingBotryococcus) make 2.31% and 2.39% of AFDW, respectively.Botryococcus, detritus and other algae comprised 67.2% of AFDW and it was suspected that more than half of this was contributed byBotryococcus. Blue-green algae, which were especially abundant in the diet during the dry season, November–February, are nutritionally most important. Seasonal variation in algal species composition could influence the quality of food ingested by the fish. 相似文献
70.
Long-term perspective on the dynamics of brown tide blooms in Long Island coastal bays 总被引:1,自引:0,他引:1
Brown tide, a bloom of the picoplankter Aureococcus anophagefferens, first appeared in eastern Long Island (Suffolk County) waters in the late spring of 1985, at about the same time it emerged, although to a lesser degree, in Narraganset Bay, RI. Since then, it has recurred sporadically in Suffolk County, and blooms have been reported in New Jersey, Delaware, Maryland, and only one other area of the world, Saldanha Bay, South Africa. Bloom initiation and maintenance within Suffolk County appear to be related to A. anophagefferens’ ability to use dissolved organic nitrogen (DON) during periods of limited dissolved inorganic nitrogen (DIN) availability. Factors controlling DIN availability include groundwater influx related to meteorological conditions, introduction of septic leachate from on-site wastewater treatment systems, and biological removal. The complexity of bloom dynamics is illustrated by a cascade of events in Great South Bay involving shellfish clearing rates, a macroalgal bloom, and microbial decomposition. 相似文献