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101.
Stephen J. Assinder Lisa V.J. Eynstone R. Peter Shellis George H. Dibdin 《FEMS microbiology letters》1995,134(2-3):287-292
Abstract The pac gene encoding the penicillin G acylase (PGA) of Bacillus megaterium ATCC 14945 has been cloned in Escherichia coli HB101 ( proA, leuB ) using a selective minimal medium containing phenylacetyl-L-leucine instead of L-leucine. The nucleotide sequence of this gene has been determined and contains an open reading frame of 2406 nucleotides. The deduced amino acid sequence shows significant similarity with other β-lactam acylases. Although the PGA of B. megaterium is extracellular, the enzyme produced in E. coli appears to have a cytoplasmic localization. 相似文献
102.
Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ14C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of 14C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought. 相似文献
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Organisms used as model genomics systems are maintained as isogenic strains, yet evidence of sequence differences between independently maintained wild-type stocks has been substantiated by whole-genome resequencing data and strain-specific phenotypes. Sequence differences may arise from replication errors, transposon mobilization, meiotic gene conversion, or environmental or chemical assault on the genome. Low frequency alleles or mutations with modest effects on phenotypes can contribute to natural variation, and it has proven possible for such sequences to become fixed by adapted evolutionary enrichment and identified by resequencing. Our objective was to identify and analyze single locus genetic defects leading to RNAi resistance in isogenic strains of Caenorhabditis elegans. In so doing, we uncovered a mutation that arose de novo in an existing strain, which initially frustrated our phenotypic analysis. We also report experimental, environmental, and genetic conditions that can complicate phenotypic analysis of RNAi pathway defects. These observations highlight the potential for unanticipated mutations, coupled with genetic and environmental phenomena, to enhance or suppress the effects of known mutations and cause variation between wild-type strains. 相似文献
105.
Quantifying marine snow as a food choice for zooplankton using stable silicon isotope tracers 总被引:1,自引:0,他引:1
Aggregates of biogenic origin >0.5 mm, known as marine snow,represent a concentrated potential source of food for zooplankton.Little is known, however, about whether aggregates are commonlygrazed by zooplankton in the field. While previous laboratorystudies have shown that the euphausiid Euphausia pacifica, andthe copepod, Calanus pacificus, common crustacean zooplankters,consume marine snow if it is the only food source available,it is not known if euphausiids will select marine snow in thepresence of edible dispersed cells, as readily occurs in nature.To examine this question, we offered E. pacifica the diatom,Nitzschia angularis in aggregated and dispersed form as preysimultaneously. Aggregates and dispersed food contained identicalcell types so that differing prey quality, taste or motilitywould not be a factor. A new method was developed to track foodsources by labeling the frustules of aggregated cells with differentnaturally occurring, but rare, stable isotopes of silicon, 30Siand 29Si. Food selection was then estimated by measuring theisotopic composition of silica within fecal pellets producedby animals feeding on mixtures of the two labeled foods. Resultsindicate that E. pacifica consumed both aggregates and dispersedcells, even when more cells were made available in dispersedform than in aggregated form. This suggests that aggregatesmay indeed be a food source in the field, even when dispersedcells are relatively abundant. The method of labeling diatomcells with stable isotopes of silica may prove useful for futuregrazing experiments to distinguish identical cell types. 相似文献
106.
Open‐circuit voltages of lead‐halide perovskite solar cells are improving rapidly and are approaching the thermodynamic limit. Since many different perovskite compositions with different bandgap energies are actively being investigated, it is not straightforward to compare the open‐circuit voltages between these devices as long as a consistent method of referencing is missing. For the purpose of comparing open‐circuit voltages and identifying outstanding values, it is imperative to use a unique, generally accepted way of calculating the thermodynamic limit, which is currently not the case. Here a meta‐analysis of methods to determine the bandgap and a radiative limit for open‐circuit voltage is presented. The differences between the methods are analyzed and an easily applicable approach based on the solar cell quantum efficiency as a general reference is proposed. 相似文献
107.
Lisa Palmer 《The Australian journal of anthropology》2020,31(2):224-239
In north central Timor‐Leste, multi‐sensory ecological engagement is deeply entangled with conceptualisations of and approaches to people’s wellbeing. How people understand human health and wellbeing is closely related to how they understand nature or more particularly human/nature relations and distinctions across multiple timescales. Working through complex cosmopolitics and activated through cross‐temporal more‐than‐human ‘mutualities of being’, kinship networks are attuned to relational flows between ‘bodies’ and things. Rather than concentrating on the disjunctions created by the differences in the natures of beings or their ritual separation, this paper examines how relational flows between such ‘bodies’ and things open up cosmopolitical spaces for the creation and negotiation of intergenerational wellbeing. 相似文献
108.
Stobbe Astrid Rasbach Gabriele Röpke Astrid Rühl Lisa 《Vegetation History and Archaeobotany》2020,29(2):133-151
Vegetation History and Archaeobotany - Waldgirmes in Hesse (Germany) is one of the oldest Roman towns east of the Rhine River. It was founded in 3 bc and abandoned after ad 9, probably in ad 16,... 相似文献
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