The authors demonstrate that the electric conductivities of cubic and hexagonal boron nitride (c-BN and h-BN) thin films increased markedly by the in situ doping of zinc. The doped films were electrically semiconducting, and conductivities at room temperature increased from 10−8to10−2Ω−1cm−1 with increasing zinc concentration from 400to20000ppm. Activation energies for electric conduction (Ec) of c-BN decreased from 0.3to0.1eV with increasing zinc concentration, suggesting feasible shallow-level doping. On the other hand, h-BN thin films showed approximately 0.1eV higher Ec than those of c-BN’s, due to the formation of defective B–B bonds.

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Molecular biology techniques for nematode community analysis that are high throughput and operable by non-experts are in high demand for soil biological assessments. In the development of such techniques, the closeness of the analytical results to those obtained by conventional methods is of key importance. In this context, we compared similarity relationships of nematode community structures between polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) and individual-based morphological identification (CONV) using 12 nematode samples recovered from crop field soils in four localities in Japan. First, we determined whether the primer set chosen to amplify the 18s rRNA genes of nematode taxa was suitable for DGGE by comparing community structures of four selected samples between clone libraries (CLs) and those revealed by CONV. We considered the primer set to be suitable because we found significant correlations in the structures between CLs and CONV in three of the four samples examined. Then we determined the community structure of 12 samples by both DGGE and CONV, and calculated distance matrices to examine if analytical results were similar between the two methods. The correlations in matrices were 0.400-0.603, depending on the types of distance measures, and were always significant between the two methods. In comparing dendrograms drawn based on the matrices, DGGE and CONV were actually similar to some extent in that samples from a single locality tended to group together, although some localities were split in DGGE. We also conducted DGGE with four additional selected samples to confirm that the band pattern (i.e., number, position and relative intensity) was consistent in each sample across subsamples and gels. Given these results, we expect DGGE to become a useful and efficient tool for nematode community analysis, especially for non-experts, but our method of evaluation has limitations and more tests are needed.

The objective of the present study was to increase understanding of the effects of heavy metal pollution and soil properties on microorganisms in relation to the biomass and microbial functional community. Soil samples were collected from aged polluted and reference sites on a floodplain. The soil Cu, Zn and Pb total concentrations were much higher at the polluted sites (average 231.6-309.9 mg kg −1 , 195.7-233.0 mg kg −1 , and 72.4-86.0 mg kg −1 , respectively) than at the reference site (average 33.3-44.0 mg kg −1 , 76.7-98.0 mg kg −1 , and 30.8-41.6 mg kg −1 , respectively), while the available heavy metal concentrations in CaCl 2 extraction were similar in all sites. Small seasonal variations in the size of microbial biomass were observed. Ambient soil properties (e.g. total C, N, pH, moisture content, and CEC) affected the soil microbial biomass more than the heavy metal pollution. However, the aged pollution tended to impact on the composition of the microbial community. PICT (pollution-induced community tolerance) test using BIOLOG Ecoplates showed enhanced tolerance of the microbial community to Cu stress in the polluted site. In non polluted but low nutrient, low pH and low moisture soil, the microbial biomass was lower and the microbial community was more vulnerable to Cu stress. In spite of the low heavy metal availability due to ageing, the BIOLOG technique provided sensitive detection of microbial community level changes in PICT analysis.

We simultaneously examined the bacteria, fungi and nematode communities in Andosols from four agro-geographical sites in Japan using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and statistical analyses to test the effects of environmental factors including soil properties on these communities depending on geographical sites. Statistical analyses such as Principal component analysis (PCA) and Redundancy analysis (RDA) revealed that the compositions of the three soil biota communities were strongly affected by geographical sites, which were in turn strongly associated with soil characteristics such as total C (TC), total N (TN), C/N ratio and annual mean soil temperature (ST). In particular, the TC, TN and C/N ratio had stronger effects on bacterial and fungal communities than on the nematode community. Additionally, two-way cluster analysis using the combined DGGE profile also indicated that all soil samples were classified into four clusters corresponding to the four sites, showing high site specificity of soil samples, and all DNA bands were classified into four clusters, showing the coexistence of specific DGGE bands of bacteria, fungi and nematodes in Andosol fields. The results of this study suggest that geography relative to soil properties has a simultaneous impact on soil microbial and nematode community compositions. This is the first combined profile analysis of bacteria, fungi and nematodes at different sites with agricultural Andosols.