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21.
A unique feature of the shrimp, Rimicaris exoculata , from the Rainbow hydrothermal vent field is the abundance of iron oxyhydroxides in its branchial chamber. These minerals accumulate throughout the molting cycle and are intimately associated with the shrimps' epibiotic microflora. In this study, an enhancement of the iron oxidation rate through shrimp swarms in the vicinity of vents is highlighted. This process is sustained by the high molting frequency of the shrimp, and potentially has large biogeochemical and ecological consequences for the associated hydrothermal ecosystem. The calculated rate for abiotic (homogeneous and heterogeneous) iron oxidation suggests that autocatalytic oxidation is the predominant reaction pathway leading to the accumulation of iron oxyhydroxides throughout the molting cycle. The occurrence of iron-oxidizing bacteria is not excluded, but their growth is most probably restricted to the first molting stage when competition with the abiotic iron oxidation is low. The influence of epibiont activity on local oxygen conditions and on the surface properties of the formed mineral, combined with the position of the shrimp in the hydrothermal mixing gradient, is expected to drive the relative contribution of abiogenic and biogenic iron oxidation. 相似文献
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SANDRA NOIR THOMAS COLBY ANNE HARZEN JÜRGEN SCHMIDT RALPH PANSTRUGA 《Molecular Plant Pathology》2009,10(2):223-236
Conidiospores are the asexual propagation units of many plant-pathogenic fungi. In this article, we report an annotated proteome map of ungerminated conidiospores of the ascomycete barley powdery mildew pathogen, Blumeria graminis f.sp. hordei . Using a combination of two-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, we have identified the proteins in 180 spots, which probably represent at least 123 distinct fungal gene products. Most of the identified proteins have a predicted function in carbohydrate, lipid or protein metabolism, indicating that the spore is equipped for the catabolism of storage compounds as well as for protein biosynthesis and folding on germination. 相似文献
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LINDA FUSELIER PAUL G. DAVISON MARIAH CLEMENTS BLANKA SHAW NICOLAS DEVOS JOCHEN HEINRICHS J
RN HENTSCHEL MARKO SABOVLJEVIC PTER SZ
VNYI SCOTT SCHUETTE WOLFGANG HOFBAUER A. JONATHAN SHAW 《Biological journal of the Linnean Society. Linnean Society of London》2009,98(4):745-756
Seed plant genera often exhibit intercontinental disjunctions where different species are found on different continents. Many morphologically circumscribed bryophyte species exhibit similar disjunctions. We used nucleotide sequences from the plastid and nuclear genomes to test hypotheses of phylogeography within representatives of the genus Metzgeria: Metzgeria furcata, Metzgeria conjugata, and Metzgeria myriopoda. The first two species have sexual and asexual populations, exhibit disjunctions between North America and Europe, and have been split into separate species, numerous subspecies or varieties. The third species occurs in eastern North America but is not reported from Europe. Phylogenetic analyses resolved three distinct lineages within the morphologically defined species, M. furcata: one in North America, and two in Europe. Similarly, three morphologically cryptic clades of M. conjugata were resolved by the molecular data: northern North America, Europe, and south‐eastern North America. For both species, molecular divergence among taxa occurred in the absence of morphological change. In the case of M. myriopoda, all plants from eastern North America were both morphologically uniform and genetically homogeneous (although not identical). The present study provides significant insight into a plant group with complex taxonomy, and indicates that these liverwort taxa with wide distributions, extreme sex ratios, and continental disjunctions harbor cryptic lineages. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 745–756. 相似文献
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We estimate the global bioenergy potential from dedicated biomass plantations in the 21st century under a range of sustainability requirements to safeguard food production, biodiversity and terrestrial carbon storage. We use a process‐based model of the land biosphere to simulate rainfed and irrigated biomass yields driven by data from different climate models and combine these simulations with a scenario‐based assessment of future land availability for energy crops. The resulting spatial patterns of large‐scale lignocellulosic energy crop cultivation are then investigated with regard to their impacts on land and water resources. Calculated bioenergy potentials are in the lower range of previous assessments but the combination of all biomass sources may still provide between 130 and 270 EJ yr?1 in 2050, equivalent to 15–25% of the World's future energy demand. Energy crops account for 20–60% of the total potential depending on land availability and share of irrigated area. However, a full exploitation of these potentials will further increase the pressure on natural ecosystems with a doubling of current land use change and irrigation water demand. Despite the consideration of sustainability constraints on future agricultural expansion the large‐scale cultivation of energy crops is a threat to many areas that have already been fragmented and degraded, are rich in biodiversity and provide habitat for many endangered and endemic species. 相似文献
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The polytenization of rRNA cistrons in Drosophila species is studied in an attempt to follow the course of under-representation of heterochromatic compared with euchromatic chromosome regions. 相似文献
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