Genetic and biochemical characterization of Bacillus subtilis 168 mutants specifically blocked in the synthesis of the teichoic acid poly(3-O-beta-D-glucopyranosyl-N-acetylgalactosamine 1-phosphate): gneA, a new locus, is associated with UDP-N-acetylglucosamine 4-epimerase activity

The resistance spectrum to bacteriophage phi 3T of different Bacillus subtilis 168/W23 strains hybrid for wall teichoic acids suggested that poly(3-O-beta-D-glucopyranosyl-N-acetylgalactosamine 1-phosphate), a so-called minor teichoic acid of strain 168, forms part of the receptor for this phage, and a serologically related group of phages. A representative sample of 25 mutants specifically resistant to phi 3T, obtained from a mutagenized culture by direct selection, were all found to have a greatly reduced galactosamine content. Relevant mutations in these strains were shown by PBS1 transduction and transformation to belong to two linkage groups; a minority, associated with an atypical colony morphology, were localized between sacA and purA, whereas the majority mapped between gtaB and tagB1 (formerly tag-1), a region containing all known genes involved in the synthesis of the major wall teichoic acid, poly(glycerol phosphate). The former mutations mapped in a new locus, gneA, characterized by a deficiency in UDP-N-acetylglucosamine 4-epimerase, while the latter ones, as well as the previously identified pha-3 (Estrela et al., 1986, Journal of General Microbiology 132, 411-415), map is a locus named gga. They are likely to affect membrane-bound enzymes involved in the synthesis of the galactosamine-containing teichoic acid. A possible biological role of this polymer is discussed.