| Autor: |
Clemans, Daniel L., Kolenbrander, Paul E., Debabov, Dmitri V., Zhang, Qunying, Lunsford, R. Dwayne, Sakone, Holly, Whittaker, Catherine J., Heaton, Michael P., Neuhaus, Francis C. |
| Zdroj: |
Infection and Immunity; May 1999, Vol. 67 Issue: 5 p2464-2474, 11p |
| Abstrakt: |
ABSTRACTMost human oral viridans streptococci participate in intrageneric coaggregations, the cell-to-cell adherence among genetically distinct streptococci. Two genes relevant to these intrageneric coaggregations were identified by transposon Tn916mutagenesis ofStreptococcus gordoniiDL1 (Challis). A 626-bp sequence flanking the left end of the transposon was homologous todltAand dltBof Lactobacillus rhamnosusATCC 7469 (formerly called Lactobacillus casei). A 60-kb probe based on this flanking sequence was used to identify the homologous DNA in a fosmid library of S. gordoniiDL1. This DNA encodedd-alanine-d-alanyl carrier protein ligase that was expressed in Escherichia colifrom the fosmid clone. The cloned streptococcal dltAwas disrupted by inserting anermAMcassette, and then it was linearized and transformed into S. gordoniiDL1 for allelic replacement. Erythromycin-resistant transformants containing a single insertion indltAexhibited a loss of d-alanyl esters in lipoteichoic acid (LTA) and a loss of intrageneric coaggregation. This phenotype was correlated with the loss of a 100-kDa surface protein reported previously to be involved in mediating intrageneric coaggregation (C. J. Whittaker, D. L. Clemans, and P. E. Kolenbrander, Infect. Immun. 64:4137–4142, 1996). The mutants retained the parental ability to participate in intergeneric coaggregation with human oral actinomyces, indicating the specificity of the mutation in altering intrageneric coaggregations. The mutants were altered morphologically and exhibited aberrant cell septa in a variety of pleomorphs. The natural DNA transformation frequency was reduced 10-fold in these mutants. Southern analysis of chromosomal DNAs from various streptococcal species with the dltAprobe revealed the presence of this gene in most viridans streptococci. Thus, it is hypothesized that d-alanyl LTA may provide binding sites for the putative 100-kDa adhesin and scaffolding for the proper presentation of this adhesin to mediate intrageneric coaggregation. |
| Databáze: |
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