Isolation of H. pylori Genomic DNA and Restriction Analysis.

Since Helicobacter pylori was first described in 1983 (1), the study of genomic DNA has been central to the development of its microbiology and molecular genetics. For instance, DNA base composition estimation (mol% G+C) was crucial in demonstrating affinities of the microorganism to the genus Campylobacter (2). Likewise, DNA-DNA hybridization assays revealed a high degree of base sequence homology between different isolates of H. pylori, yet a low relatedness to Campylobacter fetus and other species of Campylobacter (3). In 1987, rRNA-DNA hybridization and hybrid thermal stability analyses were used to show that H. pylori was phylogenetically distinct from Campylobacter sensu stricto and that the species merited classification in a new genus (4). The most significant application of DNA analysis has been in showing the diversity between genomes of different strains within H. pylori. The first indication of such genome diversity was from restriction endonuclease digest analysis of genomic DNA (6) and was subsequently confirmed by ribosomal RNA gene analysis and polymerase chain reaction (PCR)-based analysis of urease and other genes (7).