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1.
Microcoleus chthonoplastes constitutes one of the dominant microorganisms in intertidal microbial mat communities. In the laboratory, the effects of
repeated daily exposure to ultraviolet radiation (16:8 light:dark cycle) was investigated in unicyanobacterial cultures isolated
from three different localities (Baltic Sea = WW6; North Sea = STO and Brittany = BRE). Photosynthesis and growth were measured
in time series (12–15 days) while UV-absorbing mycosporine-like amino acids (MAAs) and cellular integrity were determined
after 12 and 3 days exposure to three radiation treatments [PAR (22 μmol photon m−2 s−1) = P; PAR + UV-A (8 W m−2) = PA; PAR + UV-A + UV-B (0.4 W m−2) = PAB]. Isolate-specific responses to UVR were observed. The proximate response to radiation stress after 1-day treatment
showed that isolate WW6 was the most sensitive to UVR. However, repeated exposure to radiation stress indicated that photosynthetic
efficiency (F
v/F
m) of WW6 acclimated to UVR. Conversely, although photosynthesis in STO exhibited lower reduction in F
v/F
m during the first day, the values declined over time. The BRE isolate was the most tolerant to radiation stress with the lowest
reduction in F
v/F
m sustained over time. While photosynthetic efficiencies of different isolates were able to acclimate to UVR, growth did not.
The discrepancy seems to be due to the higher cell density used for photosynthesis compared to the growth measurement. Apparently,
the cell density used for photosynthesis was not high enough to offer self-shading protection because cellular damage was
also observed in those filaments under UVR. Most likely, the UVR acclimation of photosynthesis reflects predominantly the
performance of the surviving cells within the filaments. Different strategies were observed in MAAs synthesis. Total MAAs
content in WW6 was not significantly different between all the radiation treatments. In contrast, the additional fluence of
UV-A and UV-B significantly increased MAAs synthesis and accumulation in STO while only UV-B fluence significantly increased
MAAs content in BRE. Regardless of the dynamic photosynthetic recovery process and potential UV-protective functions of MAAs,
cellular investigation showed that UV-B significantly contributed to an increased cell mortality in single filaments. In their
natural mat habitat, M. chthonoplastes benefits from closely associated cyanobacteria which are highly UVR-tolerant due to the production of the extracellular UV-sunscreen
scytonemin. 相似文献
2.
Ozone depletion is highest during spring and summer in Antarctica, coinciding with the seasonal reproduction of most macroalgae.
Propagules are the life-stage of an alga most susceptible to environmental perturbations therefore, reproductive cells of
three intertidal macroalgal species Adenocystis utricularis (Bory) Skottsberg, Monostroma hariotii Gain, and Porphyra endiviifolium (A and E Gepp) Chamberlain were exposed to photosynthetically active radiation (PAR), PAR + UV-A and PAR + UV-A + UV-B radiation
in the laboratory. During 1, 2, 4, and 8 h of exposure and after 48 h of recovery, photosynthetic efficiency, and DNA damage
were determined. Saturation irradiance of freshly released propagules varied between 33 and 83 μmol photons m−2 s−1 with lowest values in P. endiviifolium and highest values in M. hariotii. Exposure to 22 μmol photons m−2 s−1 PAR significantly reduced photosynthetic efficiency in P. endiviifolium and M. hariotii, but not in A. utricularis. UV radiation (UVR) further decreased the photosynthetic efficiency in all species but all propagules recovered completely
after 48 h. DNA damage was minimal or not existing. Repeated exposure of A. utricularis spores to 4 h of UVR daily did not show any acclimation of photosynthesis to UVR but fully recovered after 20 h. UVR effects
on photosynthesis are shown to be species-specific. Among the tested species, A. utricularis propagules were the most light adapted. Propagules obviously possess good repair and protective mechanisms. Our study indicates
that the applied UV dose has no long-lasting negative effects on the propagules, a precondition for the ecological success
of macroalgal species in the intertidal. 相似文献
3.
Two experiments were performed to determine how application of the cytokinin benzyladenine (BA) influenced flowering in Doritaenopsis and Phalaenopsis orchid clones. In the first experiment, two vegetative orchid clones growing in 15-cm pots were transferred from a 28°C greenhouse
that inhibited flowering to a 23°C greenhouse for flower induction (day 0). A foliar spray (0.2 L m−2) containing BA at 100, 200, or 400 mg L−1 or 25, 50, or 100 mg L−1 each of BA and gibberellins A4 + A7 (BA+GA) was applied on days 0, 7, and 14. Plants treated with BA alone at 200 or 400 mg L−1 had a visible inflorescence 3–9 days earlier and had a mean of 0.7–3.5 more inflorescences and 3–8 more flowers per plant
than nontreated plants. The application of BA+GA had no effect on inflorescence number and total flower number at the rates
tested. In the second experiment, three orchid clones received a single foliar spray of BA at 200 mg L−1 at six time points relative to time of transfer from 29°C to 23°C (−1, 0, +1, +2, +4, or +6 weeks). A separate group of plants
received a BA application at week 0 but was maintained at 29°C. Inflorescence number was greatest in all three orchid clones
when plants were treated with BA 1 week after the temperature transfer. Plants that were sprayed with BA and maintained at
29°C did not initiate inflorescences. The promotion of flowering by the application of BA suggests that cytokinins at least
partially regulate inflorescence initiation of Doritaenopsis and Phalaenopsis, but its promotion is conditional and BA application cannot completely substitute for an inductive low temperature. 相似文献
4.
To assess the short- and long-term impacts of Ultraviolet radiation (UVR, 280–400 nm) on the red tide alga Chaetoceros curvisetus, we exposed cells to three different solar radiation treatments–PAB:280–700 nm, PA:320–700 nm, and P:400–700 nm under 20°C
incubated temperature. Short-term exposures were investigated: the photochemical efficiency (ΦPSII) versus irradiance curves under six levels of solar radiation by covering the incubators with a variable number of neutral
density screens (the irradiance thus varied from 100 to 3%) lasting 1 h, and long-term exposures were designed to assess how
the cells acclimate to solar radiation (the growth, UVabc and ratio of repair to damage rates of D1 protein were detected). A significant decrease in the photochemical efficiency
(ΦPSII) at high irradiance (100% of incident solar radiation, 261.6 Wm−2) was observed in short-term exposure (1 h). UVR-induced photoinhibition was reduced to 7% in 3% solar radiation (4.08 Wm−2), compared with 66% in 100% solar radiation (261.6 Wm−2). In long-term experiments (11 days) using batch cultures, cell densities during the first 6 days were relatively constant
for treatment P, and decreased slightly under PA and PAB treaments, reflecting a change in the irradiance experienced in the
laboratory to that of incident solar irradiance. Thereafter, cell density increased and UV-induced photoinhibition decreased
with the following days, indicating acclimation to solar UV. At the end of experiment, cells were found to exhibit both higher
ratios of repair to UV-related damage and increased concentrations of UV-absorbing compounds, whose maximum absorption was
found to be at 329 nm. Our data indicate that C. curvisetus is sensitive to ultraviolet radiation, but was able to acclimate relatively rapidly (ca. 6 days) by synthesizing UV-absorbing
compounds and by increasing the rates of repair processes of D1 protein in PSII. 相似文献
5.
Cortinarius breviradicatus sp. nov., found in deciduous forests, is described and illustrated from Niigata, Japan. It is characterized by its medium-sized
to large dark brown basidiocarp, acutely conical pileus, and rooting stipe, and by subglobose to broadly ellipsoid basidiospores.
In addition, the extracting solution from its basidiocarps exhibits a strong fluorescence around 400–430 nm in ultraviolet
radiation (250 nm), which was observed in a species of Cortinarius sect. Orellani. The new species belongs to the section Orellani. The differences between the new taxon and similar species are briefly discussed. 相似文献
6.
The intertidal red alga Porphyra haitanensis Chang et Zheng is episodically desiccated and exposed to high levels of solar radiation at low tide during emersion. However,
little has been documented on the relationship between the stresses during desiccation and related chemical compounds. We
found that P. haitanensis thalli, when desiccated under indoor (artificial radiation) or outdoor (solar radiation) conditions, with or without UV radiation
(UVR: 280–400 nm), contained significantly higher concentrations of UV-absorbing compounds (peak at 336 nm) than those maintained
submerged (without desiccation). Solar UVR had no effect on the content of UV-absorbing compounds. Even though the concentration
of these compounds decreased with time in all treatments, a slower decrease was observed in the desiccated samples. The samples
with higher levels of UV-absorbing compounds showed higher photochemical efficiency of photosystem II (PS II) during the exposure
or subsequent recovering process than samples with low concentration of UV-absorbing compounds, reflecting their protective
role. The concentration of these compounds varied in different parts of the thallus, with the middle and marginal parts containing
60–80% more UV-absorbing compounds than the basal parts in both female and male plants. In addition, the marginal parts of
male thalli contained more UV-absorbing compounds than the corresponding parts of female thalli. Our data suggest that desiccation
plays a key role in this alga to maintain high concentration of UV-absorbing compounds, and that this might provide a beneficial
advantage to compete in the intertidal zone where the organism is normally exposed to high levels of UVR. 相似文献
7.
With a few clear exceptions (e.g., Daphnia) it is uncertain if most aquatic invertebrates can detect and respond to ultraviolet radiation (UVR). It is known that many aquatic invertebrates are vulnerable to UVR and that anthropogenically-induced increases in surface UVR have occurred in recent decades. We examined the photoresponses of late larval instars of Chaoborus punctipennis to different combinations of UVA (320–400 nm), UVB (300–320 nm) and visible light (400–700 nm) to determine whether the larvae can detect and/or avoid UVR. To accomplish this, we exposed late instar C. punctipennis larvae to a directional light source of UVR only (peak wavelength at 360 nm), visible light only or visible plus various wavebands of UVR. We examined negative phototaxis for 10 min at a quantum flux of 2.62 x 1013 quanta s–1 cm–2 (S.D. = 3.63 x 1012 quanta s–1 cm–2). In the dark, larvae stayed close to the surface of the experimental vessels. Under all treatments containing visible light the larvae exhibited negative phototaxis and occupied the bottom of the vessels. Under UVR only, the larvae occupied the middle of the water column. Our results suggest that late instar C. punctipennis larvae are unable to detect and avoid UVB and short UVA wavelengths but they can detect long UVA wavelengths. 相似文献
8.
To assess the short- and long-term impacts of UV radiation (UVR, 280–400 nm) on the microalga Scrippsiella trochoidea, we exposed cells to three different radiation treatments (PAB: 280–700 nm, PA: 320–700 nm, and P: 400–700 nm). A significant
decrease in the photochemical efficiency (ΦPSII) at high irradiance (100% of incident solar radiation, 216.0 W m−2) was observed. Photoinhibition was reduced from 62.7 to 10.9% when the cells were placed in 12% solar radiation (26.1 W m−2). In long-term experiments (11 days) using batch cultures, cell densities during the first 5 days were decreased under treaments
P, PA, and PAB, reflecting a change in the irradiance experienced in the laboratory to that of incident solar irradiance.
Thereafter, specific growth rates increased and UV-induced photoinhibition decreased, indicating acclimation to solar UV.
Cells were found to exhibit both higher ratios of repair to UV-related damage, shorter period for recovery and increased concentrations
of UV-absorbing compounds (UVabc), whose maximum absorption was found to be at 336 nm. Our data indicate that S. trochoidea is sensitive to ultraviolet radiation, but was able to acclimate relatively rapidly (ca. 6 days) by synthesizing UVabc and by increasing the rates of repair processes of D1 protein in PSII. 相似文献
9.
Nongporn Hutadilok-Towatana Wantana Reanmongkol Pharkphoom Panichayupakaranant 《Journal of applied phycology》2010,22(5):599-605
In this study, the methanol extract of Arthrospira (Spirulina) platensis was examined for acute and subchronic toxicities. The extract did not produce any sign of toxicity within 7 days after feeding
it at a single high dose of 6 g kg−1 body weight to female and male Swiss mice. For the subchronic toxicity test, the extract at doses of 6, 12, and 24 mg kg−1 body weight was orally administered to six male and six female Wistar rats daily for 12 weeks. Throughout the study period,
we did not observe any abnormalities on behavior, food and water intakes, and health status among the treated animals. The
hematology and clinical chemistry parameters of treated groups did not significantly differ from those of the controls in
both sexes. Postmortem examination of the test groups also showed no abnormalities in both gross and histological findings.
These results thus suggest that the methanol extract of A. platensis did not cause acute or subchronic toxicity in our experimental animals. 相似文献
10.
Eduardo Forján Inés Garbayo Marta Henriques Jorge Rocha José M. Vega Carlos Vílchez 《Marine biotechnology (New York, N.Y.)》2011,13(3):366-375
Nannochloropsis, a green microalga, is a source for commercially valuable compounds as extensively described and, in particular, is recognised
as a good potential source of eicosapentaenoic acid (20:5ϖ3), an important polyunsaturated fatty acid for human consumption
for prevention of several diseases. Climate change might include variation in the ultraviolet (UV) levels as one of the consequences
derived from the anthropogenic activity. This paper shows the response of Nannochloropsis cultures exposed for 7 days to UV-A (320–400 nm) added to photosynthetically active radiation (PAR; 400–700 nm). Growth rates
and photosynthetic activity were assessed to determine the impact of UV-A increased levels on the cell growth and basic metabolism
activity. Xanthophyll pigments (zeaxanthin and violaxanthin), carotenoids (canthaxanthin and β-carotene) and polyunsaturated
fatty acids (myristic, palmitic, palmitoleic, arachidonic and eicosapentaenoic acids) were measured for assessing the antioxidant
response of the microalgae to added UV-A radiation to PAR. The results show that the modulated use of UV-A radiations can
lead to increased growth rates, which are sustained in time by an increased light transduction activity. The expected antioxidant
response to the incident UV-A radiation consisted of increases in zeaxanthin and β-carotene contents—synthesis of antioxidant
carotenoids—and increases in the saturated fatty acids to polyunsaturated fatty acids ratio. The results suggest that modulated
UV-A radiation can be used as a tool to stimulate value molecules accumulation in microalgae through an enhanced both light
transduction process and antioxidant response, while sustaining cell growth. 相似文献
11.
Ling Zhao Yongming Bao Jingyun Wang Boshi Liu Lijia An 《World journal of microbiology & biotechnology》2009,25(1):57-64
A mutant designated as UV-3 was obtained from wild-type Enterobacter aerogenes 10293 through u.v. radiation. The activities of α-acetolactate decarboxylase (Ald), lactate dehydrogenase (Ldh) and diacetyl
reductase (Dr) in UV-3 were strongly attenuated, with the lowest activities at pH 7.0–7.5, and temperature between 36 and
39°C. Compared to the wild-type, the yield of diacetyl by UV-3 was increased 18.7-fold, up to 1.05 ± 0.01 g l−1. Acetoin and ethanol productions were decreased by 48.4 and 71.4%, respectively, but acetate yield was increased by 34.6%.
Optimum medium for diacetyl production by UV-3 contained 10% glucose, 0.5% peptone, 0.5% yeast extract powder, 0.01% (NH4)2SO4, 0.1% citric acid, 0.2% MnSO4 and 0.2% MgSO4, and this was determined by one-factor-at-a-time approach. Data from the five level central composite designs demonstrated
that initial pH of 7.0, temperature of 37°C and rotational speed of 180 rev/min were optimum processing parameters for diacetyl
production. The maximum yield of diacetyl could reach 1.35 g l−1 in a 5-l bioreactor. These results showed an enhancement of the non-enzymatic oxidative decarboxylation of α-acetolactate
and a decrease in the activities of Ald, Ldh and Dr as a consequence of diacetyl accumulation in UV-3. 相似文献
12.
An indoor sun simulator was used to provide elevated UV-B radiation (280–315 nm) in combination with realistic ratios to PAR
(400–700 nm) and UV-A radiation (315–400 nm) in order to test the physiological response of a soil- and snow microalga during
a three-day stress scenario, which may occasionally occur in their respective arctic and alpine habitats. 相似文献
13.
Fawzeia H. Elmhalli Katinka Pålsson Jan Örberg Thomas G. T. Jaenson 《Experimental & applied acarology》2009,48(3):251-262
The toxicity of para-menthane-3,8-diol (PMD), the main arthropod-repellent compound in the oil of the lemon eucalyptus, Corymbia citriodora, was evaluated against nymphs of Ixodes ricinus using five methods (A–E) of a contact toxicity bioassay. Mortality rates were estimated by recording numbers of dead nymphs
at 30 min intervals during the first 5 h after the start of exposure and at longer intervals thereafter. The mortality rate
increased with increasing concentration of PMD and duration of exposure with a distinct effect after 3.5 h. From the results
obtained by methods A, C and E, the LC50 range was 0.035–0.037 mg PMD/cm2 and the LC95 range was 0.095–0.097 mg PMD/cm2 at 4 h of exposure; the LT50 range was 2.1–2.8 h and the LT95 range was 3.9–4.2 h at 0.1 mg PMD/cm2. To determine the duration of toxic activity of PMD, different concentrations (0.002, 0.01, 0.1 mg PMD/cm2) were tested and mortality was recorded at each concentration after 1 h; thereafter new ticks were tested. This test revealed
that the lethal activity of PMD remained for 24 h but appeared absent after 48 h. The overall results show that PMD is toxic
to nymphs of I. ricinus and may be useful for tick control. 相似文献
14.
The presence of the anaerobic spore former Clostridium in Arthrospira platensis destined for human consumption is generally not assessed during quality assurance procedures. As this nutraceutical is administered
as complementary medicine to the immunocompromised, this study aimed to investigate the presence of these potential pathogens.
Anaerobic counts performed on tablets from a single manufacturer indicated an excess of 105 CFU/endospores g−1 tablet for three different A. platensis batches. Tests for coliforms for use as “indicators” of pathogens in the tablets were negative. Using classic culture techniques,
five species of Clostridium were isolated. Subsequent use of PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting of tablets showed a divergent
microbial population, with a predominance of anaerobic endospore formers, including Clostridium. Sequencing of a 1.5 kb 16S rDNA clone library and phylogenetic analyses of prominent operational taxonomic units confirmed
the presence of an additional five Clostridium spp. and other genera in the tablets. A composite molecular ladder, using 16S rRNA DGGE amplicons of 17 representative bacterial
species was constructed to assist in identifying anaerobes present in tablets sourced from three different A. platensis manufacturers. Results indicated that commercial A. platensis preparations were contaminated with potentially hazardous clostridia and other anaerobic species. Results suggest that certain
commercial A. platensis preparations require stringent microbial quality assurance measures to ensure safe use as a nutraceutical for the immunocompromised
and the general public. 相似文献
15.
16.
Chitwadee Phithakrotchanakoon Ratama Daduang Arinthip Thamchaipenet Thidarat Wangkam Toemsak Srikhirin Lily Eurwilaichitr Verawat Champreda 《Applied microbiology and biotechnology》2009,82(1):131-140
A polyhydroxyalkanote depolymerase gene from Thermobifida sp. isolate BCC23166 was cloned and expressed as a C-terminal His6-tagged fusion in Pichia pastoris. Primary structure analysis revealed that the enzyme PhaZ-Th is a member of a proposed new subgroup of SCL-PHA depolymerase
containing a proline–serine repeat linker. PhaZ-Th was expressed as two glycosylated forms with apparent molecular weights
of 61 and 70 kDa, respectively. The enzyme showed esterase activity toward p-nitrophenyl alkanotes with V
max and K
m of 3.63 ± 0.16 μmol min−1 mg−1 and 0.79 ± 0.12 mM, respectively, on p-nitrophenyl butyrate with optimal activity at 50–55°C and pH 7–8. Surface plasmon resonance (SPR) analysis demonstrated that
PhaZ-Th catalyzed the degradation of poly-[(R)-3-hydroxybutyrate] (PHB) films, which was accelerated in (R)-3-hydroxyvalerate copolymers with a maximum degradation rate of 882 ng cm−2 h−1 for poly[(R)-3-hydroxybutyrate-co-3-hydroxyvalerate] (12 mol% V). Surface deterioration, especially on the amorphous regions of PHB films
was observed after exposure to PhaZ-Th by atomic force microscopy. The use of P. pastoris as an alternative recombinant system for bioplastic degrading enzymes in secreted form and a sensitive SPR analytical technique
will be of utility for further study of bioplastic degradation. 相似文献
17.
Nguyen VN Oh IJ Kim YJ Kim KY Kim YC Park RD 《Journal of industrial microbiology & biotechnology》2009,36(2):195-203
Two extracellular chitinases were purified from Paecilomyces variotii DG-3, a chitinase producer and a nematode egg-parasitic fungus, to homogeneity by DEAE Sephadex A-50 and Sephadex G-100 chromatography.
The purified enzymes were a monomer with an apparent molecular mass of 32 kDa (Chi32) and 46 kDa (Chi46), respectively, and
showed chitinase activity bands with 0.01% glycol chitin as a substrate after SDS-PAGE. The first 20 and 15 N-terminal amino
acid sequences of Chi32 and Chi46 were determined to be Asp-Pro-Typ-Gln-Thr-Asn-Val-Val-Tyr-Thr-Gly-Gln-Asp-Phe-Val-Ser-Pro-Asp-Leu-Phe
and Asp-Ala-X-X-Tyr-Arg-Ser-Val-Ala-Tyr-Phe-Val-Asn-Trp-Ala, respectively. Optimal temperature and pH of the Chi32 and Chi46
were found to be both 60°C, and 2.5 and 3.0, respectively. Chi32 was almost inhibited by metal ions Ag+ and Hg2+ while Chi46 by Hg2+ and Pb2+ at a 10 mM concentration but both enzymes were enhanced by 1 mM concentration of Co2+. On analyzing the hydrolyzates of chitin oligomers [(GlcNAc)
n
, n = 2–6)], it was considered that Chi32 degraded chitin oligomers as an exo-type chitinase while Chi46 as an endo-type chitinase. 相似文献
18.
19.
Hai-Nan Su Bin-Bin Xie Xiu-Lan Chen Jin-Xia Wang Xi-Ying Zhang Bai-Cheng Zhou Yu-Zhong Zhang 《Journal of applied phycology》2010,22(1):65-70
Allophycocyanin (APC) is a minor component of phycobiliproteins in cyanobacteria and red algae. This paper describes a simple
and inexpensive extracting method for isolating APC from Spirulina (Arthrospira) platensis with high efficiency. The crude phycobiliprotein extract was pretreated by ammonium sulfate fractionation. Then, by adding
hydroxylapatite into crude phycobiliprotein extract dissolved in 20 mM phosphate buffer (pH 7.0), APC was selectively adsorbed
by hydroxylapatite but C-phycocyanin (C-PC) was not. The hydroxylapatite was collected and APC was extracted from the crude
phycobiliprotein extract. Then, the enriched APC was washed off from the hydroxylapatite using 100 mM phosphate buffer (pH 7.0).
In this simple extracting method it was easy to remove C-PC and isolate APC in large amounts. The absorbance ratio A
650/A
280 of extracted APC reached 2.0. The recovery yield was 70%, representing 4.61 mg · g−1 wet weight. The extracted APC could be further purified by a simple anion-exchange chromatography with a pH gradient from
5.6 to 4.0. The absorbance ratio A
650/A
280 of the purified APC reached 5.0, and the overall recovery yield was 43%, representing 2.83 mg · g−1 wet weight. Its purity was confirmed by native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate-PAGE. 相似文献
20.
Erkang Yin Yilin Le Jianjun Pei Weilan Shao Qiyin Yang 《World journal of microbiology & biotechnology》2008,24(2):275-280
According to the amino acid sequence, a codon-optimized xylanase gene (xynA1) from Thermomyces lanuginosus DSM 5826 was synthesized to construct the expression vector pHsh-xynA1. After optimization of the mRNA secondary structure in the translational initiation region of pHsh-xynA1, free energy of the 70 nt was changed from −6.56 to −4.96 cal/mol, and the spacing between AUG and the Shine-Dalgarno sequence
was decreased from 15 to 8 nt. The expression level was increased from 1.3 to 13% of total cell protein. A maximum xylanase
activity of 47.1 U/mL was obtained from cellular extract. The recombinant enzyme was purified 21.5-fold from the cellular
extract of Escherichia coli by heat treatment, DEAE-Sepharose FF column and t-Butyl-HIC column. The optimal temperature and pH were 65 °C and pH 6.0,
respectively. The purified enzyme was stable for 30 min over the pH range of 5.0–8.0 at 60 °C, and had a half-life of 3 h
at 65 °C. 相似文献