Wall teichoic acids are anionic phosphate-rich polymers that are part of the complex meshwork of carbohydrates that make up the gram-positive cell wall. These polymers are essential to the proper rod-shaped morphology of
Bacillus subtilisand have been shown to be an important virulence determinant in the nosocomial opportunistic pathogen Staphylococcus aureus. Together, sequence-based studies, in vitro experiments with biosynthetic proteins, and analyses of the chemical structure of wall teichoic acid have begun to shed considerable light on our understanding of the biogenesis of this polymer. Nevertheless, some paradoxes remain unresolved. One of these involves a putative duplication of genes linked to CDP-ribitol synthesis ( tarI′ J′ and tarIJ) as well as poly(ribitol phosphate) polymerization ( tarKand tarL) in S. aureus. In the work reported here, we performed careful studies of the dispensability of each gene and discovered a functional redundancy in the duplicated gene clusters. We were able to create mutants in either of the putative ribitol phosphate polymerases (encoded by tarKand tarL) without affecting teichoic acid levels in the S. aureuscell wall. Although genes linked to CDP-ribitol synthesis are also duplicated, a null mutant in only one of these ( tarI′ J′) could be obtained, while tarIJremained essential. Suppression analysis of the tarIJnull mutant indicated that the mechanism of dysfunction in tarI′ J′ is due to poor translation of the TarJ′ enzyme, which catalyzes the rate-limiting step in CDP-ribitol formation. This work provides new insights into understanding the complex synthetic steps of the ribitol phosphate polymer in S. aureusand has implications on specifically targeting enzymes involved in polymer biosynthesis for antimicrobial design.