当前位置： SCI文献检索 > JOURNAL OF BACTERIOLOGY期刊下所有文献 > Transcriptional regulation of Aggregatibacter actinomycetemcomitans lsrACDBFG and lsrRK operons and their role in biofilm formation.

Transcriptional regulation of Aggregatibacter actinomycetemcomitans lsrACDBFG and lsrRK operons and their role in biofilm formation.

Abstract：

:Autoinducer-2 (AI-2) is required for biofilm formation and virulence of the oral pathogen Aggregatibacter actinomycetemcomitans, and we previously showed that lsrB codes for a receptor for AI-2. The lsrB gene is expressed as part of the lsrACDBFG operon, which is divergently transcribed from an adjacent lsrRK operon. In Escherichia coli, lsrRK encodes a repressor and AI-2 kinase that function to regulate lsrACDBFG. To determine if lsrRK controls lsrACDBFG expression and influences biofilm growth of A. actinomycetemcomitans, we first defined the promoters for each operon. Transcriptional reporter plasmids containing the 255-bp lsrACDBFG-lsrRK intergenic region (IGR) fused to lacZ showed that essential elements of lsrR promoter reside 89 to 255 bp upstream from the lsrR start codon. Two inverted repeat sequences that represent potential binding sites for LsrR and two sequences resembling the consensus cyclic AMP receptor protein (CRP) binding site were identified in this region. Using electrophoretic mobility shift assay (EMSA), purified LsrR and CRP proteins were shown to bind probes containing these sequences. Surprisingly, the 255-bp IGR did not contain the lsrA promoter. Instead, a fragment encompassing nucleotides +1 to +159 of lsrA together with the 255-bp IGR was required to promote lsrA transcription. This suggests that a region within the lsrA coding sequence influences transcription, or alternatively that the start codon of A. actinomycetemcomitans lsrA has been incorrectly annotated. Transformation of ΔlsrR, ΔlsrK, ΔlsrRK, and Δcrp deletion mutants with lacZ reporters containing the lsrA or lsrR promoter showed that LsrR negatively regulates and CRP positively regulates both lsrACDBFG and lsrRK. However, in contrast to what occurs in E. coli, deletion of lsrK had no effect on the transcriptional activity of the lsrA or lsrR promoters, suggesting that another kinase may be capable of phosphorylating AI-2 in A. actinomycetemcomitans. Finally, biofilm formation of the ΔlsrR, ΔlsrRK, and Δcrp mutants was significantly reduced relative to that of the wild type, indicating that proper regulation of the lsr locus is required for optimal biofilm growth by A. actinomycetemcomitans.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Torres-Escobar A,Juárez-Rodríguez MD,Lamont RJ,Demuth DR

doi

10.1128/JB.01476-12

subject

Has Abstract

pub_date

2013-01-01 00:00:00

pages

56-65

issue

eissn

0021-9193

issn

1098-5530

pii

JB.01476-12

journal_volume

195

pub_type

杂志文章

在线工具

Transcriptional regulation of Aggregatibacter actinomycetemcomitans lsrACDBFG and lsrRK operons and their role in biofilm formation.