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991.
Meta-analysis: the past, present and future 总被引:1,自引:0,他引:1
992.
Wide geographical and ecological distribution of nitrogen and carbon gains from fungi in pyroloids and monotropoids (Ericaceae) and in orchids 总被引:4,自引:2,他引:2
* Stable isotope abundance analyses recently revealed that some European green orchids and pyroloids (Ericaceae) are partially myco-heterotrophic, exploiting mycorrhizal fungi for organic carbon and nitrogen. Here we investigate related species to assess their nutritional mode across various forest and climate types in Germany and California. * C- and N-isotope signatures of five green pyroloids, three green orchids and several obligate myco-heterotrophic species (including the putatively fully myco-heterotrophic Pyrola aphylla) were analysed to quantify the green plants' nutrient gain from their fungal partners and to investigate the constancy of enrichment in (13)C and (15)N of fully myco-heterotrophic plants from diverse taxa and locations relative to neighbouring autotrophic plants. * All green pyroloid and one orchid species showed significant (15)N enrichment, confirming incorporation of fungi-derived N compounds while heterotrophic C gain was detected only under low irradiance in Orthilia secunda. Pyrola aphylla had an isotope signature equivalent to those of fully myco-heterotrophic plants. * It is demonstrated that primarily N gain from mycorrhizal fungi occurred in all taxonomic groups investigated across a wide range of geographical and ecological contexts. The (13)C and (15)N enrichment of obligate myco-heterotrophic plants relative to accompanying autotrophic plants turned out as a fairly constant parameter. 相似文献
993.
Jeffrey M. Klopatek 《Plant and Soil》2007,294(1-2):157-167
Litterfall and fine root production were measured for three years as part of a carbon balance study of three forest stands
in the Pacific Northwest of the United States. A young second-growth Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stand, a second-growth Douglas-fir with red alder (Alnus rubra Bong.) stand, and an old-growth (∼550 years) Douglas-fir stand were monitored for inputs of carbon and nitrogen into the
soil from litterfall and fine root production, as well as changes in soil C and N. Fine root production and soil nutrient
changes were measured through the use of soil ingrowth bags containing homogenized soil from the respective stands. Litterfall
biomass was greatest in the Douglas-fir-alder stand (527 g m−2 yr−1) that annually returned nearly three times the amount of N as the other stands. Mean residence time for forest floor material
was also shortest at this site averaging 4.6 years and 5.5 years for C an N, respectively. Fine root production in the upper
20 cm ranged from 584 g m−2 in the N rich Douglas-fir-alder stand to 836 g m−2 in the old-growth stand. Fine root production (down to one meter) was always greater than litterfall with a below:above ratio
ranging from 3.73 for the young Douglas-fir stand to 1.62 for the Douglas-fir-alder stand. The below:above N ratios for all
three stands closely approximate those for biomass. Soil changes in both C and N differed by site, but the soil C changes
in the old-growth stand mirrored those obtained in an ongoing CO2 flux study. Results from the soil ingrowth bags strongly suggest that this method provides a simple, but sufficient device
for measuring potential fine root biomass production as well as soil chemical changes. 相似文献
994.
Boreal forests are increasing in age partly due to reduced logging and efficient wildfire control. As a result, they also
stock more carbon. Whether increased forest C stock causes greater production of dissolved organic carbon (DOC) is uncertain.
DOC in bulk precipitation, throughfall and soil water was studied in 10-, 30-, 60- and 120-year-old stands of Norway spruce
(Picea abies (L.) Karst.) DOC concentrations in throughfall and O horizon soil water followed the order 10 < 30 < 60 = 120 and 10 = 30 < 120 < 60,
respectively. DOC fluxes followed the order 10 = 30 < 60 = 120 in throughfall, while no significant difference between stands
was found for O horizon soil water. Above-ground tree litter varied according to 10 < 30 < 60 = 120, a pattern identical to
that for DOC concentrations in throughfall and resembling but not identical to that for DOC concentrations in O horizon soil
water. This indicates additional sources for DOC in soil water. Seasonality in DOC concentrations was observed at the base
of the O horizon, and seasonality in DOC fluxes in both throughfall and O horizon soil water. Our results suggest differences
in the polarity of DOC between the 10-year stand and the others, which we interpret as reflecting the lack of grown trees
and possibly the different vegetation on the 10-year stand. 相似文献
995.
<Emphasis Type="Italic">Bacillus megaterium</Emphasis>—from simple soil bacterium to industrial protein production host 总被引:2,自引:0,他引:2
Vary PS Biedendieck R Fuerch T Meinhardt F Rohde M Deckwer WD Jahn D 《Applied microbiology and biotechnology》2007,76(5):957-967
Bacillus megaterium has been industrially employed for more than 50 years, as it possesses some very useful and unusual enzymes and a high capacity
for the production of exoenzymes. It is also a desirable cloning host for the production of intact proteins, as it does not
possess external alkaline proteases and can stably maintain a variety of plasmid vectors. Genetic tools for this species include
transducing phages and several hundred mutants covering the processes of biosynthesis, catabolism, division, sporulation,
germination, antibiotic resistance, and recombination. The seven plasmids of B. megaterium strain QM B1551 contain several unusual metabolic genes that may be useful in bioremediation. Recently, several recombinant
shuttle vectors carrying different strong inducible promoters and various combinations of affinity tags for simple protein
purification have been constructed. Leader sequences-mediated export of affinity-tagged proteins into the growth medium was
made possible. These plasmids are commercially available. For a broader application of B. megaterium in industry, sporulation and protease-deficient as well as UV-sensitive mutants were constructed. The genome sequence of
two different strains, plasmidless DSM319 and QM B1551 carrying seven natural plasmids, is now available. These sequences
allow for a systems biotechnology optimization of the production host B. megaterium. Altogether, a “toolbox” of hundreds of genetically characterized strains, genetic methods, vectors, hosts, and genomic sequences
make B. megaterium an ideal organism for industrial, environmental, and experimental applications. 相似文献
996.
Kiviharju K Moilanen U Leisola M Eerikäinen T 《Applied microbiology and biotechnology》2007,73(6):1267-1274
The behavior of Streptomyces peucetius var. caesius N47 was studied in a glucose limited chemostat with a complex cultivation medium. The steady-state study yielded the characteristic
constants μ
max over 0.10 h−1, Y
XS 0.536 g g−1, and mS 0.54 mg g−1 h−1. The product of secondary metabolism, ɛ-rhodomycinone, was produced with characteristics Y
PX 12.99 mg g−1 and m
P 1.20 mg g−1 h−1. Significant correlations were found for phosphate and glucose consumption with biomass and ɛ-rhodomycinone production. Metabolic
flux analysis was conducted to estimate intracellular fluxes at different dilution rates. TCA, PPP, and shikimate pathway
fluxes exhibited bigger values with production than with growth. Environmental perturbation experiments with temperature,
airflow, and pH changes on a steady-state chemostat implied that an elevation of pH could be the most effective way to shift
the cells from growing to producing, as the pH change induced the biggest transient increase to the calculated ɛ-rhodomycinone
flux. 相似文献
997.
Davey K 《Journal of insect physiology》2007,53(1):1-10
This printed version of the Wigglesworth Lecture reviews the evidence that juvenile hormone (JH) acts on the follicular epithelium of the ovary through a membrane receptor to control access of yolk proteins to the oocyte surface. The thyroid hormones mimic this action through the same receptor. Conversely, both JH III and 3,5,3′ triiodothyronine (T3) increase the activity of Ca ATPase in isolated erythrocyte membrane preparations from sheep, apparently through the same membrane receptor. These effects are mimicked by exposure of the respective tissues to CO2. These findings suggest that the hormones arose as biotic signals, originally using existing CO2 receptors. 相似文献
998.
Fei‐Xue Fu Mark E. Warner Yaohong Zhang Yuanyuan Feng David A. Hutchins 《Journal of phycology》2007,43(3):485-496
Little is known about the combined impacts of future CO2 and temperature increases on the growth and physiology of marine picocyanobacteria. We incubated Synechococcus and Prochlorococcus under present‐day (380 ppm) or predicted year‐2100 CO2 levels (750 ppm), and under normal versus elevated temperatures (+4°C) in semicontinuous cultures. Increased temperature stimulated the cell division rates of Synechococcus but not Prochlorococcus. Doubled CO2 combined with elevated temperature increased maximum chl a–normalized photosynthetic rates of Synechococcus four times relative to controls. Temperature also altered other photosynthetic parameters (α, Φmax, Ek, and ) in Synechococcus, but these changes were not observed for Prochlorococcus. Both increased CO2 and temperature raised the phycobilin and chl a content of Synechococcus, while only elevated temperature increased divinyl chl a in Prochlorococcus. Cellular carbon (C) and nitrogen (N) quotas, but not phosphorus (P) quotas, increased with elevated CO2 in Synechococcus, leading to ~20% higher C:P and N:P ratios. In contrast, Prochlorococcus elemental composition remained unaffected by CO2, but cell volume and elemental quotas doubled with increasing temperature while maintaining constant stoichiometry. Synechococcus showed a much greater response to CO2 and temperature increases for most parameters measured, compared with Prochlorococcus. Our results suggest that global change could influence the dominance of Synechococcus and Prochlorococcus ecotypes, with likely effects on oligotrophic food‐web structure. However, individual picocyanobacteria strains may respond quite differently to future CO2 and temperature increases, and caution is needed when generalizing their responses to global change in the ocean. 相似文献
999.
1000.
Leila J. Hamdan Robert B. Jonas 《Journal of experimental marine biology and ecology》2007,342(2):242-252
Phytoplankton production and accumulation of extracellular organic carbon (EOC) was tracked during diel intervals in microcosms by inhibiting bacterioplankton assimilation of EOC with streptomycin and kanamycin. Bacterioplankton production (3H-thymidine incorporation) and metabolism (14C-glucose incorporation) were monitored in samples collected from the Potomac River estuary to determine the effect of the antibiotics. Particulate (i.e., raw water) primary production and EOC (i.e., water passing through 1.0 μm glass fiber filter) production rates were monitored to determine the impact of antibiotics on phytoplankton. In preliminary experiments, neither streptomycin nor kanamycin alone significantly inhibited bacterioplankton activity compared to controls, but when both were present secondary production and metabolism were reduced up to 90%, and remained as such for 45 h. During field evaluations using a streptomycin and kanamycin mixture (50 μM each) particulate primary production and EOC production were not statistically different in control and antibiotic treated samples indicating that the antibiotics did not negatively influence phytoplankton production rates. In the presence of antibiotics dissolved free amino acids (DFAA) and, to a lesser extent, monosaccharides were significantly elevated compared to controls. This study demonstrates that streptomycin and kanamycin are capable of inhibiting bacterioplankton metabolism and uptake of dissolved organic carbon (DOC) in the samples tested so that the contribution of EOC to the DOC pool and to bacterioplankton metabolism could be measured and assessed. 相似文献