[Distribution characteristics of lead in different particle size fractions of surface soil of a lead-acid battery factory contaminated site].

In this research, six topsoil samples (0-20 cm) were collected in the heavy-metal lead contaminated soil of one lead battery factory in south-west China as research object, which were later divided into seven particle size fractions, and analyzed for the lead concentration as well as the correlation between the lead concentration and the organic matter content. The result showed that five soil samples were contaminated with lead with different pollution levels, and there were two different trends in the changes of lead concentration as of the change of soil particle size. The lead concentration of the three samples from sewage treatment workshop, the workshop A and the workshop B, showed a first declining and then ascending trend with the decreasing particle size. The lead concentration of the soil samples of the packing workshop and the former production workshop A showed a decreasing trend when the particle size decreased. The lead concentration and the organic matter content showed a positive linear correlation (R2 = 0.8232). Soil organic matter has the ability of lead enrichment, and the ability declines with the decreasing particle size. Soil texture may be an important factor for the interaction between soil organic matter and lead distribution.

[Gene expression, purification and functional analysis of LiPrmA].

Leptospira interrogans (L. interrogans) genomic DNA was used as template to amplify the full-length gene for ribosomal protein L11 methyltransferase (liPrmA) by PCR. The pET22b-/liprmA expression plasmid was successfully constructed in Escherichia coli (E.coli.) strain TOP10 and confirmed by restriction enzyme digest and sequencing. Through optimizing expression of the recombinant liPrmA-6xHis fusion protein in expression host E. coli. BL21, the yield of soluble target protein reached 40 mg (liter culture)-1. The LiPrmA was purified to apparent homogeneity in a single step using Ni-NTA His Bind chromatography. Amino acid homologous analysis showed that liPrmA shared significant identity with other prokaryotic PrmA and eukaryotic putative PrmA in the catalytic region including AdoMet binding domain. Methylation activity experiments showed purified liPrmA was able to catalyze the ribosomal protein L11 of L. interrogans methylated under the presence of S-adenosyl-methionine (AdoMet).