title: Combined subtraction hybridization and polymerase chain reaction amplification procedure for isolation of strain-specific Rhizobium DNA sequences.
abstract: A novel subtraction hybridization procedure, incorporating a combination of four separation strategies, was developed to isolate unique DNA sequences from a strain of Rhizobium leguminosarum bv. trifolii. Sau3A-digested DNA from this strain, i.e., the probe strain, was ligated to a linker and hybridized in solution with an excess of pooled subtracter DNA from seven other strains of the same biovar which had been restricted, ligated to a different, biotinylated, subtracter-specific linker, and amplified by polymerase chain reaction to incorporate dUTP. Subtracter DNA and subtracter-probe hybrids were removed by phenol-chloroform extraction of a streptavidin-biotin-DNA complex. NENSORB chromatography of the sequences remaining in the aqueous layer captured biotinylated subtracter DNA which may have escaped removal by phenol-chloroform treatment. Any traces of contaminating subtracter DNA were removed by digestion with uracil DNA glycosylase. Finally, remaining sequences were amplified by polymerase chain reaction with a probe strain-specific primer, labelled with 32P, and tested for specificity in dot blot hybridizations against total genomic target DNA from each strain in the subtracter pool. Two rounds of subtraction-amplification were sufficient to remove cross-hybridizing sequences and to give a probe which hybridized only with homologous target DNA. The method is applicable to the isolation of DNA and RNA sequences from both procaryotic and eucaryotic cells.
authors.affiliation: Food and Agricultural Microbiology Research Division, Department of Agriculture for Northern Ireland, Belfast.
authors.forename: A J
authors.initials: AJ
authors.lastname: Bjourson
authors.forename: C E
authors.initials: CE
authors.lastname: Stone
authors.forename: J E
authors.initials: JE
authors.lastname: Cooper
mesh_terms: D001483:Base Sequence; D015342:DNA Probes; D004269:DNA, Bacterial / Q000235:genetics* / Q000302:isolation & purification; D005069:Evaluation Studies as Topic; D005784:Gene Amplification; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction / Q000379:methods*; D016961:Rhizobium leguminosarum / Q000235:genetics*; D013045:Species Specificity
chemical_list: D015342:DNA Probes; D004269:DNA, Bacterial