In:
Journal of Bacteriology, American Society for Microbiology, Vol. 183, No. 21 ( 2001-11), p. 6324-6334
Abstract:
The dlt operon of gram-positive bacteria comprises four genes ( dltA, dltB, dltC , and dltD ) that catalyze the incorporation of d -alanine residues into the lipoteichoic acids (LTAs). In this work, we characterized the dlt operon of Streptococcus agalactiae , which, in addition to the dltA to dltD genes, included two regulatory genes, designated dltR and dltS , located upstream of dltA . The dltR gene encodes a 224-amino-acid putative response regulator belonging to the OmpR family of regulatory proteins. The dltS gene codes for a 395-amino-acid putative histidine kinase thought to be involved in the sensing of environmental signals. The dlt operon of S. agalactiae is mainly transcribed from the P dltR promoter, which directs synthesis of a 6.5-kb transcript encompassing dltR, dltS, dltA, dltB, dltC , and dltD , and from a weaker promoter, P dltA , which is located in the 3′ extremity of dltS . We demonstrate that P dltR , but not P dlA , is activated by DltR in the presence of DltS in d -Ala-deficient LTA mutants resulting from insertional inactivation of the dltA gene, which encodes the cytoplasmic d -alanine- d -alanyl carrier ligase DltA. Expression of the dlt operon does not require DltR and DltS, since the basal activity of P dltR is high, being 20-fold that of the constitutive promoter P aphA-3 which directs synthesis of the kanamycin resistance gene aphA-3 in various gram-positive bacteria. We hypothesize that the role of DltR and DltS in the control of expression of the dlt operon is to maintain the level of d -Ala esters in LTAs at a constant and appropriate value whatever the environmental conditions. The DltA − mutant displayed the ability to form clumps in standing culture and exhibited an increased susceptibility to the cationic antimicrobial polypeptide colistin.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
DOI:
10.1128/JB.183.21.6324-6334.2001
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2001
detail.hit.zdb_id:
1481988-0
SSG:
12
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