Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Characterization of a Novel β-Glucosidase-Like Activity from a Soil Metagenome: Chengjian Jiang , Gefei Ma , Shuangxi Li , Tingting Hu , Zhiqun Che , Peihong Shen , Bing Yan , Bo Wu; J. Microbiol. 2009;47(5):542-548. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-009-0024-y

Abstract: We report the cloning of a novel β-glucosidase-like gene by function-based screening of a metagenomic library from uncultured soil microorganisms. The gene was named bgl1C and has an open reading frame of 1,443 base pairs. It encodes a 481 amino acid polypeptide with a predicted molecular mass of about 57.8 kDa. The deduced amino acid sequence did not show any homology with known β-glucosidases. The putative β-glucosidase gene was subcloned into the pETBlue-2 vector and overexpressed in E. coli Tuner (DE3) pLacІ; the recombinant protein was purified to homogeneity. Functional characterization with a high performance liquid chromatography method demonstrated that the recombinant Bgl1C protein hydrolyzed D-glucosyl-β-(1-4)-D-glucose to glucose. The maximum activity for Bgl1C protein occurred at pH 8.0 and 42°C using p-nitrophenyl-β-D-glucoside as the substrate. A CaCl2 concentration of 1 mM was required for optimal activity. The putative β-glucosidase had an apparent Km value of 0.19 mM, a Vmax value of 4.75 U/mg and a kcat value of 316.7/min under the optimal reaction conditions. The biochemical characterization of Bgl1C has enlarged our understanding of the novel enzymes that can be isolated from the soil metagenome.

Analysis of nifH Gene Diversity in Red Soil Amended with Manure in Jiangxi, South China: Qihui Teng , Bo Sun , Xinrui Fu , Shunpeng Li , Zhongli Cui , Hui Cao; J. Microbiol. 2009;47(2):135-141. Published online May 2, 2009; DOI: https://doi.org/10.1007/s12275-008-0184-1

Abstract: In order to understand the community structure of diazotrophs in red soil and effects of organic manure application on the structure, four nifH gene libraries were constructed: the control (CK), low manure (LM), high manure (HM), and high manure adding lime (ML). Totally 150 nifH gene clones were screened and grouped into 21 clusters by RFLP analysis. Existence of dominant patterns was observed in all libraries, which counted for over 96% of clones in library HM and about 56~72% in other three libraries. The nifH sequences of the dominant patterns in all libraries were most similar to sequences of the cyanobacteria. nifH genes showed high diversity in red soil, dispersing throughout the nifH clades (alpha-, beta-, and gamma-Proteobacteria, Firmicutes, cyanobacteria, Verrucomicrobia, and posited group). Bradyrhizobium and Burkholderia were also important diazotrophs in low fertility soil samples. Low manure treatment increased the diversity of nifH genes compared with CK and high manure treatments. Manure and lime treatment led to obvious community succession. Total N to available P ratio, total carbon, and K concentrations were the main factors affecting the diversity of diazotrophs in red soil.

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