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941.
Deciduous forests may respond differently from coniferous forests to the anthropogenic deposition of nitrogen (N). Since fungi,
especially ectomycorrhizal (EM) fungi, are known to be negatively affected by N deposition, the effects of N deposition on
the soil microbial community, total fungal biomass and mycelial growth of EM fungi were studied in oak-dominated deciduous
forests along a nitrogen deposition gradient in southern Sweden. In-growth mesh bags were used to estimate the production
of mycelia by EM fungi in 19 oak stands in the N deposition gradient, and the results were compared with nitrate leaching
data obtained previously. Soil samples from 154 oak forest sites were analysed regarding the content of phospholipid fatty
acids (PLFAs). Thirty PLFAs associated with microbes were analysed and the PLFA 18:2ω6,9 was used as an indicator to estimate
the total fungal biomass. Higher N deposition (20 kg N ha−1 y−1 compared with 10 kg N ha−1 y−1) tended to reduce EM mycelial growth. The total soil fungal biomass was not affected by N deposition or soil pH, while the
PLFA 16:1ω5, a biomarker for arbuscular mycorrhizal (AM) fungi, was negatively affected by N deposition, but also positively
correlated to soil pH. Other PLFAs positively affected by soil pH were, e.g., i14:0, a15:0, 16:1ω9, a17:0 and 18:1ω7, while
some were negatively affected by pH, such as i15:0, 16:1ω7t, 10Me17:0 and cy19:0. In addition, N deposition had an effect
on the PLFAs 16:1ω7c and 16:1ω9 (negatively) and cy19:0 (positively). The production of EM mycelia is probably more sensitive
to N deposition than total fungal biomass according to the fungal biomarker PLFA 18:2ω6,9. Low amounts of EM mycelia covaried
with increased nitrate leaching, suggesting that EM mycelia possibly play an important role in forest soil N retention at
increased N input. 相似文献
942.
Factors influencing the spatial distribution of forest plant species in hedgerows of North-western Germany 总被引:2,自引:0,他引:2
In North-western Germany woodland fragmentation has caused a decline in many forest plant species. Hedgerows partly offer
a similar environment as forests and have been identified as potential habitats for forest plants in various studies from
North America and Western Europe. The objective of this study was to examine whether this applies also to Central Europe and
which variables affect the spatial distribution and abundance of forest plant species in hedgerows on a local scale. Three
hedgerow networks north of the city of Bremen, Germany, were selected as study areas and divided into totally 515 hedgerow
segments. In each segment we recorded all vascular plants and a large number of explanatory variables relating to structure,
spatial configuration, environment and management. Averaged across species there was a predominant effect of environmental
factors on the occurrence of forest species in the hedgerows, followed by spatial configuration and management. Hedgerow structure
was found to be less important. In general, forest species were favored by low nutrient and light availability as well as
high connectivity with other hedgerows or forest; they avoided hedgerows with a west-easterly orientation and an adjacent
land use in the form of fields or grasslands. Forest species found and not found in hedgerows did not differ in their environmental
preferences or life history traits. The number of threatened forest species in the hedgerows, however, was lower than expected
with respect to their overall proportion to the total number of forest species in the region. 相似文献
943.
João Marcelo Alvarenga Braga 《Kew Bulletin》2008,63(2):309-314
Summary
Calathea dryadica and Calathea reginae are described, circumscribed and illustrated. These new species are probably endemic to the Atlantic Forest of Rio de Janeiro
State in Southeast Brazil and are considered critically endangered because of the restricted geographic area of occurrence,
sometimes enclosed by densely urbanised areas. 相似文献
944.
Laura Bedin Denardi Jéssica Tairine Keller Vanessa Oliveira Débora Alves Nunes Mario Janio Morais Santurio Sydney Hartz Alves 《Mycopathologia》2017,182(9-10):819-828
In this study, we evaluated the in vitro activity of echinocandins, azoles, and amphotericin B alone and in combination against echinocandin/azole-sensitive and echinocandin/azole-resistant Candida glabrata isolates. Susceptibility tests were performed using the broth microdilution method in accordance with the Clinical and Laboratory Standards Institute document M27-A3. The checkerboard method was used to evaluate the fractional inhibitory concentration index of the interactions. Cross-resistance was observed among echinocandins; 15% of the isolates resistant to caspofungin were also resistant to anidulafungin and micafungin. Synergistic activity was observed in 70% of resistant C. glabrata when anidulafungin was combined with voriconazole or posaconazole. Higher (85%) synergism was found in the combination of caspofungin and voriconazole. The combinations of caspofungin with fluconazole, posaconazole and amphotericin B, micafungin with fluconazole, posaconazole and voriconazole, and anidulafungin with amphotericin B showed indifferent activities for the majority of the isolates. Anidulafungin combined with fluconazole showed the same percentage of synergism and indifference (45%). Antagonism was detected in 50% of isolates when micafungin was combined with amphotericin B. Combinations of echinocandins and antifungal azoles have great potential for in vivo assays which are required to evaluate the efficacy of these combinations against multidrug-resistant C. glabrata strains. 相似文献
945.
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
946.
Cold adaptation in the phytopathogenic fungi causing snow molds 总被引:1,自引:0,他引:1
Snow molds are psychrophilic or psychrotrophic fungal pathogens of forage crops, winter cereals, and conifer seedlings. These
fungi can grow and attack dormant plants at low temperatures under snow cover. In this review, we describe the biodiversity
and physiological and biochemical characteristics of snow molds that belong to various taxa. Cold tolerance is one of the
important factors related to their geographic distribution, because snow molds develop mycelia under snow cover and because
they should produce intra- and extracellular enzymes active at low temperatures for growth and infection. Basidiomycetous
snow molds produce extracellular antifreeze proteins. Their physiological significance is to keep the extracellular environment
unfrozen. The psychrophilic ascomycete Sclerotia borealis shows normal mycelial growth under frozen conditions, which is faster than that on unfrozen media at optimal growth temperature.
This fungus does not produce extracellular antifreeze proteins, but osmotic stress tolerance enables the fungus to grow at
subzero temperatures. In conclusion, different taxa of snow molds have different strategies to adapt under snow cover. 相似文献
947.
Xiaolian Gu Ping Zhuang Feng Zhao Xiaotao Shi Xiaorong Huang Guangpeng Feng Tao Zhang Jianyi Liu Longzhen Zhang Boyd Kynard 《Environmental Biology of Fishes》2017,100(1):27-33
Experiments were conducted in artificial stream tanks with juvenile Chinese sturgeon, Acipenser sinensis, captured in the Yangtze Estuary to test two null hypotheses (1) juveniles have no preference for white or black substrates, and (2) white or black substrate color has no effect on juvenile feeding efficiency on the barcheek goby,Rhinogobius giurinus, a dark-colored prey of wild juveniles. Juveniles strongly preferred white substrate. However, in feeding tests, feeding efficiency by juveniles was similar on white or black substrates. Thus, substrate color had no effect on feeding efficiency. Results suggest the innate preference for white substrate is not a visual adaptation for capturing prey on a contrasting background, but is an adaptation predisposing juveniles to seek light-colored sandy substrate where forage abundance is greatest. 相似文献
948.
A β-glucosidase effectively releasing diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW), named AfG, was purified from a strain of Aspergillus fumigates. The molecular weight of AfG was 113 kDa. Analysis of protein fragments by ESI-Q-TOF indicated that AfG was a β-glucosidase.
The circular dichroism spectrum suggested that the main secondary structure of AfG in Milli-Q water was α-helixes. Atomic
force microscopy revealed that it was a globular protein. AfG maintained high activity from pH 3.6 to 5.0 and from 50 to 90°C.
With the strong heat stability, AfG retained 55% of its original activity at 65°C for 120 h. AfG utilized muti-3-O-glycosides
of various steroidal saponins from DZW as substrate, such as trillin, diosgenin diglucoside, dioscin, deltonin and gracillin,
to yield diosgenin, suggesting the possibility of producing diosgenin from total saponins of DZW using a single enzyme. 相似文献
949.
Attached media reactors are used for enhancement of wastewater treatment processes including anaerobic condition. Selection of a suitable biofilm carrier is a compelling method to improve anaerobic digestion systems. This study investigates the performance of four fibrous biofilms installed in batch biogas reactors for treatment of cow manure. BioCords HS1, HS2, LS1, and LS2 are manufactured by Bishop Water Technologies, ON, Canada. Effluents and attached growth media were analyzed after batch experiment; methane production, methane yield, transfer efficiencies, organic and solid removal efficiencies, pH, and attached volatile suspended solid (VSS) were measured; VSS attached to biofilms mainly correlated with the specific surface area of each biofilm. Additionally, SEM (scanning electron microscopy) was used for further understanding of biofilm formation process for BioCords and the dissimilarity in their performance. The results indicated that BioCord LS2 had positive impact on achieving higher methane production and removal efficiencies compared to other support media utilized in batch reactors. It was also demonstrated from the experiment that BioCord LS2 potentially could generate higher methane production than conventional batch bioreactor. 相似文献
950.
This study explored a consumer-resource model including reproductive and nonreproductive subpopulations of the consumer to
consider whether resource-dependent reproductive adjustment by the consumer would stabilize consumer-resource dynamics. The
model assumed that decreasing (increasing) resource availability caused reproductive suppression (facilitation), and that
the reproductive consumer had a higher mortality rate than the nonreproductive one (i.e., a trade-off between reproduction
and survival). The model predicted that the variability would be reduced when the consumer had a strong tendency to suppress
reproduction in response to low resource availability or when the cost of reproduction was high, although consumer extinction
became more likely. Furthermore, when the consumer-resource dynamics converged to limit cycles, reproductive adjustment enhanced
the long-term average of the consumer density. It was also predicted that if reproductive suppression enhanced resource consumption
efficiency (i.e., a trade-off between reproduction and foraging), then it would destabilize the system by canceling the stabilizing
effect of the reproductive adjustment itself. These results suggest that it is necessary not only to identify the costs of
reproduction, but also to quantify the changes in individual-level performances due to reproduction in order to understand
the ecological consequences of reproductive adjustment. 相似文献