RESUMO
The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in Ryugu samples and found that they are dominated by presolar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have different abundances among the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating a ~5 million year exposure, and from implanted solar wind record the recent irradiation history of Ryugu after it migrated to its current orbit.
RESUMO
The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial 3He/4He and 20Ne/22Ne ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth's atmospheric gas is the best explanation for the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed on the basis of the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid.
RESUMO
Haemophilus parasuis is an important respiratory tract pathogen of swine and the etiological agent of Glässer's disease. The molecular pathogenesis of H. parasuis is not well studied, mainly due to the lack of efficient tools for genetic manipulation of this bacterium. In this study we describe a Tn5-based random mutagenesis method for use in H. parasuis. A novel chloramphenicol-resistant Tn5 transposome was electroporated into the virulent H. parasuis serovar 5 strain 29755. High transposition efficiency of Tn5, up to 10(4) transformants/µg of transposon DNA, was obtained by modification of the Tn5 DNA in the H. parasuis strain HS071 and establishment of optimal electrotransformation conditions, and a library of approximately 10,500 mutants was constructed. Analysis of the library using transposon-directed insertion-site sequencing (TraDIS) revealed that the insertion of Tn5 was evenly distributed throughout the genome. 10,001 individual mutants were identified, with 1561 genes being disrupted (69.4% of the genome). This newly-developed, efficient mutagenesis approach will be a powerful tool for genetic manipulation of H. parasuis in order to study its physiology and pathogenesis.
