A. A scheme of xanthine (X) and hypoxanthine (H) conversion into nucleotides. R-1-P, ribose-1-phosphate; R-5-P, ribose-5-phosphate; PRPP, 5-phosphorybosyl-1-pyrophosphate. Isolated inactivational and overproductional suppressors on the “hypoxanthine side” are indicated by spiked and smooth ovals, correspondingly. The corresponding genes on the “xanthine side” (guaA, gpt and xapA) are in bold. B. The effect of “missing suppressors” on the degree of rdgB recA co-inhibition. The values are means of four-five independent measurements ± SE. C. Slowing the overall metabolism with chloramphenicol marginally increases growth of the double mutant. The values are means of four independent measurements ± SE (in most cases, masked by the size of the symbols). D. Slowing growth of wild type cells with thinner media marginally increases growth of the double mutant. 20 AA, all aminoacids added, according to the recipe of Neidhardt (Neidhardt et al., 1974); 6 AA, the six aminoacids that AB1157 requires (arginine, glutamine, histidine, leucine, proline, and threonine) are added. The values are means of three independent measurements ± SE.