Hybridization reactions on a DNA macroarray membrane containing 254 PCR products that are representative of H. pylori strain 26695 (41 ubiquitous genes + 213 non-ubiquitous or strain-specific genes). Bacterial DNAs from 120 isolates involved in various diseases, including chronic gastritis (yellow), intestinal metaplasia (pink), duodenal ulcer (blue) and gastric MZBL (green), were tested by hybridization. Isolates are listed on the horizontal axis, and the genes tested, on the vertical axis. Clustering (genesis software) was carried out using the continuous values from 120 heterologous hybridization experiments, where each value corresponds to the (log26695-logheterol.strain) value for each tested gene (see materials & methods). Colors of the line range from blue, if the gene is present, to red, if absent. The range of intermediate colors reflects the degree of hybridization and thus homology, but also the redundancy of the tested genes. This figure represents the clustering based on the complete set of 254 genes.