GSE131423
Genome-wide map of Flagx3-DnaA bound to DNA in exponentially growing Sinorhizobium meliloti cultures
The genome of Sinorhizobium meliloti, a model for studying plant-bacteria symbiosis, contains the genes coding for eight LuxR-like proteins. Two of these, SinR and ExpR, are essential for quorum sensing (QS). Roles and regulation surrounding the others are mostly unknown. Here, we reveal the DNA recognition sequence and regulon of the LuxR-like protein SMc00877. Unlike ExpR, which uses the long chain acyl homoserine lactones (AHLs) as inducers, SMc00877 functioned independently of AHLs and was even functional in Escherichia coli. A target of SMc00877 is sinR, the major regulator of AHL production in S. meliloti. Disruption of SMc00877 decreased AHL production. A weaker production of AHLs resulted in smaller microcolonies, starting from single cells, and delayed AHL dependent regulation. SMc00877 was expressed only in growing cells in the presence of replete nutrients. Therefore, we renamed it NurR (nutrient sensitive LuxR-like regulator). We traced this nutrient-sensitive expression to transcription control by the DNA replication initiation factor, DnaA, which is essential for growth. These results indicate that NurR has a role in modulating the threshold of QS activation according to growth. We propose growth behavior as an additional prerequisite to population density for the activation of QS in S. meliloti. Overall design: This data includes a control and a sample, both with replicates. The control contains genomic DNA from the wild type strain, the sample contains genomic DNA enriched via Flag-tagged DnaA crosslinked to the DNA. The only difference between the wild type strain and the sample was the presence of an N-terminal Flag tag on the protein DnaA. The Flag-tagged DnaA/DNA complex was captured using anti-Flag beads.