These observations match earlier data that described detectable levels of metabolism of NeuNAc in most oral streptococci, while sialidase activity could only

be found in few species [32]. Amongst the oral streptococci, pneumococci carry a composite locus, probably assembled from the gene pool of related species. The association of the SPG1594 oxidoreductase with ManNAc metabolism and of two small hypothetical proteins (SPG1586 and SPG1588) with NeuNAc metabolism remains RepSox clinical trial unexplained, as all necessary enzymes for sialic acid metabolism appear to be already present. The PTS transporter, found to transport glucosamine, appears to be unique in pneumococci [23]. The fact that glucosamine is the last metabolic intermediate in sialic acid catabolism may indicate a convenience for the bacterium in co-utilisation of GlcN and ManNAc, even if it is not clear where pneumococci Selleckchem AZD5363 should feed on GlcN, a rare sugar in the human nasopharynx, but of which on the contrary the pneumococcal cell wall is exceptionally

rich [33]. When pneumococci grow on ManNAc and NeuNAc as the sole carbon sources, the generation time is much longer than on glucose or on the yeast-extract derived carbohydrates of the CAT medium, which is in accordance with previous data [23]. Growth on ManNAc (Figure 3B, Figure 4A) shows a profile with a change in generation time. In the case of growth on glucose repression of the whole locus indicates sequential

utilisation of sugars. This is less selleck screening library clear for the growth on yeast extract derived dextran and ManNAc, where only part of the locus is induced with the exception of the predicted central transcriptional unit encoding the principal ManNAc ABC transporter SPG1596-8. The data here presented thus do not rule out, that during growth on yeast derived sugars also ManNAc may be co-metabolised. The differential impact of regulation on the three operons Protirelin is reminiscent of data on expression of this locus in transparent colony variants, where also the nanB and ManNAc-uptake operon is not involved in differential expression, while the other two transcripts are upregulated [21]. The fact that both ManNAc and NeuNAc are able to efficiently induce the operon is in accordance with our finding that the SPG1583 regulator acts a positive regulator, as documented by absence of metabolism in its mutant and also by its annotation as a phosphor-sugar binding regulator. Since NeuNAc is imported by an ABC transporter, which does not phosphorylate during uptake, and is first hydrolysed to ManNAc before becoming phosphorylated (Figure 1B), both amino sugars may equally originate the inducer of the positive regulator; probably ManNAc-phosphate.