Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N 2 ) in the atmosphere and vexing scaling issues associated with heterogeneous soil systems. Here, we use natural abundance of N and oxygen isotopes in nitrate (NO 3 − ) to examine dentrification rates across six forest sites in southern China and central Japan, which span temperate to tropical climates, as well as various stand ages and N deposition regimes. Our multiple stable isotope approach across soil to watershed scales shows that traditional techniques underestimate terrestrial denitrification fluxes by up to 98%, with annual losses of 5.6-30.1 kg of N per hectare via this gaseous pathway. These N export fluxes are up to sixfold higher than NO 3 − leaching, pointing to widespread dominance of denitrification in removing NO 3 − from forest ecosystems across a range of conditions. Further, we report that the loss of NO 3 − to denitrification decreased in comparison to leaching pathways in sites with the highest rates of anthropogenic N deposition.denitrification | nitrate isotopes | nitrogen cycling | forested watersheds

In Neisseria gonorrhoeae, the mosaic type of penA, which encodes penicillin-binding protein 2 (PBP 2), is associated with reduced susceptibility to oral cephalosporins. To investigate the relatedness of N. gonorrhoeae clinical isolates with reduced susceptibility, we sequenced the penA genes of 32 isolates. Five different amino acid sequence types of PBP 2 were identified, but all seemed to be derivatives of pattern X of PBP 2 (PBP 2-X). However, multilocus sequence typing of the isolates showed that the isolates belonged to six different sequence types. As PBP 2-X was identified in three different sequence types, horizontal transfer of the penA allele encoding PBP2-X was suggested. We demonstrated that the penA gene could be transferred from an isolate with reduced susceptibility to a sensitive isolate by natural transformation. Comparison of the sequence of the penA-flanking regions of 12 transformants with those of the donor and the recipient suggested that at least a 4-kb DNA segment, including the penA gene, was transferred. During horizontal transfer, some of the penA alleles also acquired variations due to point mutations and genetic exchange within the allele. Our results provide evidence that the capacity for natural transformation in N. gonorrhoeae plays a role in the spread of chromosomal antibiotic resistance genes and the generation of diversity in such genes.

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SummaryNo study has documented Japanese children's food portion sizes. Since this information is essential to establish valid measurement tools and effective education methods for dietary intake, we measured them using one-day, semi-weighed diet records (DRs) for 489 Japanese children aged 3-6 y. Each food's frequency of appearance on the DRs was counted. If a child consumed a certain food more than once per day, an average weight for that food was calculated and used in the portion size calculation as that child's representative value. In total, 67 food items were consumed by twenty or more children. We calculated the mean, standard deviation, median, minimum, and maximum portion size values for these food items. In addition to these 67 items, Chinese noodles and water were included in the analysis. The most frequently consumed food was well-milled rice (mean portion size for rice579 g), which was consumed by 350 children, followed by soy sauce (4 g), eggs (26 g), and carrots (9 g). Among the five most frequently consumed foods, portion sizes of rice and pork but not milk, eggs, or carrots significantly increased with age, height, and weight. In multivariate linear regression analysis, however, the significant relationships between rice portion size and age were not observed. Regarding pork, only the relationship with height was significant. A sex difference was detected in the rice and milk portion sizes. Most of portion sizes observed here were apparently smaller than those reported among United Kingdom children. This study provides important basic information for the implementation of quantitative nutritional research and educational efforts for Japanese preschool children.