Unrooted radial tree of streptococcal zinc metalloproteinases: The tree diagram of streptococcal zinc metalloproteinases was drawn to visualise to which group the diverse proteinases of strain TIGR4 belong to. The major clusters formed by the zinc metalloproteinases of the oral streptococci are circled. The three enzymes of strain TIGR4, whose deletion mutants are assayed in this work, are boxed. Even if streptococcal zinc metalloproteinases evolve by horizontal gene transfer and show evident mosaic like structure, a fact questioning phylogenic analysis, a tree was drawn to show the major grouping of these enzymes. A stretch of 180 amino acids surrounding the active site of the streptococcal zinc metalloproteinases available from GenBank [5–8], TIGR and Sanger Centre were aligned with ClustalX using standard parameters and the tree was visualised using TreeView. S. pneumoniae proteins are preceded by Sp and the serotype. Proteins of the unfinished genomes of serotype 6 (TIGR) and 23F (Sanger Centre) are named as homologs referring to the published pneumococcal enzymes. The proteins derived from the unfinished genomes of S. gordonii and S. mitis (both TIGR) are denominated according to the respective contigs (last accessed January 27th 2003).