The relationship between microbial community structure and functional stability, tested experimentally in an upland pasture soil.

Soil collected from an upland pasture was manipulated experimentally in ways shown previously to alter microbial community structure. One set of soil was subjected to chloroform fumigation for 0, 0.5, 2, or 24 h and the other was sterilised by gamma-irradiation and inoculated with a 10(-2), 10(-4), 10(-6), or 10(-8) dilution of a soil suspension prepared from unsterilized soil. Following incubation for 8 months, to allow for the stabilization of microbial biomass and activity, the resulting microbial community structure (determined by PCR-DGGE of bacterial specific amplification products of total soil DNA) was assessed. In addition, the functional stability (defined here as the resistance and resilience of short-term decomposition of plant residues to a transient heat or a persistent copper perturbation) was determined. Changes in the active bacterial population following perturbation (determined by RT-PCR-DGGE of total soil RNA) were also monitored. The manipulations resulted in distinct shifts in microbial community structure as shown by PCR-DGGE profiles, but no significant decreases in the number of bands. These shifts in microbial community structure were associated with a reduction in functional stability. The clear correlation between altered microbial community structure and functional stability observed in this upland pasture soil was not evident when the same protocols were applied to soils in other studies. RT-PCR-DGGE profiles only detected a shift in the active bacterial population following heat, but not copper, perturbation. We conclude that the functional stability of decomposition is related to specific components of the microbial community.

High frequency of HLA-A*0207 subtype in Chinese population.

BACKGROUND: HLA-A2 is the most polymorphic and most common HLA phenotype found in various ethnic populations. Seventeen HLA-A2 subtypes have been reported and characterized by molecular techniques. Differences among these subtypes are limited to a few amino acids. Among them, HLA-A*0201 is the predominant subtype among whites. The results of a recent study, however, suggest that the HLA-A*0207 subtype may be present at a high frequency in the Chinese population. STUDY DESIGN AND METHODS: To determine the exact frequency of the HLA-A*0207 subtype in the Chinese population, genomic DNA samples obtained from 54 HLA-A2-positive Chinese in Taiwan were studied by using sequence-specific primers and polymerase chain reaction. RESULTS: HLA-A*0207 was present in 56 percent of the studied subjects. The estimated gene frequency for HLA-A*0207 is 17.8 percent in the Chinese population. CONCLUSION: HLA-A*0207 is the most common HLA-A2 subtype among Chinese. The high frequency of the HLA-A*0207 allele in this population offers a unique opportunity to study the ways in which different HLA-A2 subtypes may influence the clinical outcome of allograft transplantation and the disease susceptibility of recipients.

HLA-A, B antigens and their linkage with HLA-DR among blood donors in Taiwan.

The distribution pattern of HLA antigens varies to a great extent among different ethnic groups. Availability of HLA antigen distribution information is very important for disease association study, paternity testing and recipient/donor matching. Analysis of 11,383 blood donors from the Taipei Blood Center, Chinese Blood Services Foundation (CBSF), gave evidence that the distribution pattern of HLA-A,B antigens was unique, yet closer to Southern Chinese with higher A11, A33, B16, B40 frequencies, and B46, B48, B54 as unique antigens when compared with Caucasians. Pairwise linkage disequilibrium analysis between HLA-A, -B and -DR antigens from 238 blood donors revealed unique linkages of A33-B17, A2-B46, A11-B15, A24-B40; A11-DR5, A2-DR9, B17-DR3, B40-DR8, B13-DR2. In addition, A33-B58-DR3 were the most frequent 3-loci haplotypes. Knowing linkage disequilibrium between HLA loci and preferential association of DR specificity among various HLA-A,B haplotypes may provide a more efficient strategy to obtain an HLA-DR or HLA-D region compatible unrelated bone marrow donor from an existing HLA data bank.