tagO is involved in the synthesis of all anionic cell-wall polymers in Bacillus subtilis 168

Institut de Génétique et de Biologie Microbiennes, Université de Lausanne, Rue César-Roux 19, CH-1005 Lausanne, Switzerland 1 Author for correspondence: Dimitri Karamata. Tel: +41 21 320 60 75. Fax: +41 21 320 60 78. e-mail: dimitri.karamata{at}igbm.unil.ch Sequence homologies suggest that the Bacillus subtilis 168 tagO gene encodes UDP- N -acetylglucosamine:undecaprenyl-P N -acetylglucosaminyl 1-P transferase, the enzyme responsible for catalysing the first step in the synthesis of the teichoic acid linkage unit, i.e. the formation of undecaprenyl-PP- N -acetylglucosamine. Inhibition of tagO expression mediated by an IPTG-inducible P spac promoter led to the development of a coccoid cell morphology, a feature characteristic of mutants blocked in teichoic acid synthesis. Indeed, analyses of the cell-wall phosphate content, as well as the incorporation of radioactively labelled precursors, revealed that the synthesis of poly(glycerol phosphate) and poly(glucosyl N -acetylgalactosamine 1-phosphate), the two strain 168 teichoic acids known to share the same linkage unit, was affected. Surprisingly, under phosphate limitation, deficiency of TagO precludes the synthesis of teichuronic acid, which is normally induced under these conditions. The regulatory region of tagO , containing two partly overlapping A -controlled promoters, is similar to that of sigA , the gene encoding the major factor responsible for growth. Here, the authors discuss the possibility that TagO may represent a pivotal element in the multi-enzyme complexes responsible for the synthesis of anionic cell-wall polymers, and that it may play one of the key roles in balanced cell growth. Keywords: teichoic acid, teichuronic acid Abbreviations: GlcNAc, N -acetylglucosamine; poly(GlcGalNAcP), poly(glucosyl N -acetylgalactosamine 1-phosphate); poly(groP), poly(glycerol phosphate); TA, teichoic acid a The EMBL accession number for the nucleotide sequence reported in this paper is AJ004803.