UNCONVENTIONAL ORGANIZATION OF THE DIVISION AND CELL-WALL GENE-CLUSTER OF STREPTOCOCCUS-PNEUMONIAE

The genes responsible for cell wall biosynthesis and cell division (dc w genes) were identified and sequenced in Streptococcus pneumoniae. Th e genetic organization of the dcw cluster in Streptococcus pneumoniae differed significantly from the clusters of other bacteria reported to date. In particular, the genes corresponding to the 2 min region of t he Escherichia coli chromosome were found distributed in three genetic ally separate regions of the Streptococcus pneumoniae chromosome. The first region contained the expected ftsA and ftsZ cell division genes at one end and pbp2b, ddl and murF at the other end. The murD, murG an d divIB genes, always found located upstream of ftsA, were found in a second region separated from the first. A third region contained the y llC, yllD, pbp2x and mraY genes. The chromosomal region downstream of ftsZ was also sequenced and characterized. In Streptococcus pneumoniae this region contains four ORFs, all of unknown function, and an ORF e ncoding the Bacillus subtilis DivIVA homologue. The gene order and the organization of this region was found to be conserved in Staphylococc us aureus, Streptococcus pyogenes and Bacillus subtilis, raising the p ossibility that previously unidentified loci may also be involved in d ivision.