SUMMARY: Fifty-six mutants of 168 were selected for resistance to bacteriophages ø29 or ø25. The mutations were all linked to previously described teichoic acid markers or , for the first and last of which, the gene products have previously been identified. Each linkage group was shown to have two distinct phenotypes with respect to phage resistance and cell-wall galactosamine content. Recombination indexes of 0.35, 0.13 and 0.41 for groups A, B and C respectively were consistent with the presence of two average-sized genes in groups A and C. Correlation between genetic and phenotypic differences supported this conclusion and led to the designation of two new markers, and . Two- and three-factor transformation crosses suggested the order and . Assays for UDPglucose pyrophosphorylase and phosphoglucomutase activities in soluble extracts of representative mutants revealed that, in contrast to previous findings, the former activity was virtually undetectable in all nine group B mutants examined, suggesting that is the structural gene of this enzyme. Our results allow us to account for discrepancies with respect to previous reports. The thermosensitive mutation previously designated was shown to be 90% cotransformable with . In view of their extremely similar phenotypes the former mutation was renamed , and the likely order obtained was . This suggests that many mutations associated with deformation of cell shape in are located in the region where teichoic acid genes map.


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