Metagenomic DNA libraries

BCnietsch, A., Bowien, S., Whited, G., et al., 2003. Identification and characterization of coenzyme B-12-dependent glycerol dehydratase- and diol dehydratase-encoding genes from metagenomic DNA libraries derived from enrichment cultures. Applied and Environmental Microbiology 69,3048-3060. 

A gene (erstEl) encoding a thermostable esterase was isolated from Escherichia coli cells that had been transformed by DNA libraries with metagenomes from environmental samples isolated from thermal habitats. The enzyme belonged to the hormone-sensitive lipase family, could be overexpressed in E. coli, was active between 30 and 95°C, and used 4-nitrophenyl esters with chain lengths of C4-C16 (Rhee et al. 2005). 

Unlike the M. hentschdi KS, die KS fiiom P. aff. bulbosa displayed a much lower identity (64%) to onnamide/pederin homologs. To test whether the P aff. bulbosa KS indeed belongs to the psymberin padiway, the entire gene cluster wis isolated from a metagenomic fosmid library of 410,000 clones prepared from the total DNA of the... 

DeSantis et have reported the discovery of new nitrilases through the screening of genomic libraries created by the extraction of DNA from various environments (metagenomics). In preliminary experiments, using 25 mM mandelonitrile in pH 8 buffer containing 10% methanol and 0.12 g mL of one of these nitrilases, the acid was produced quantitatively with 98 % ee within 10 min. The product was subsequently shown to be (7 )-mandelic acid after isolation in 86 % yield. In a parallel reaction, (/ )-2-chloromande-lic acid was produced at a seventeenth of the rate (Scheme 1.44). 

Figure 2.3 Metagenomic cloning experiments. Isolation of genomic DNA directly from environments (soil, plants, mixed environments or thermal-vent worms are the examples Illustrated here) can recover DNA fragments which could encode for enzymes. The DNA fragments can be ligated to plasmids or DNA linkers, and then subjected to functional screening (expression cloning) and/or sequence analysis. Amplification by PCR can sometimes be used to yield libraries enriched with clones containing selected sequence motifs relating to families of enzymes...

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