Project description:Chemical signaling in the plant microbiome can have drastic effects on microbial community structure, and on host growth and development. Previously, we demonstrated that the auxin metabolic signal interference performed by the bacterial genus Variovorax via a novel auxin degradation locus was essential for maintaining stereotypic root development in an ecologically-relevant bacterial synthetic community. Here, we dissect the Variovorax auxin degradation locus to define the genes necessary and sufficient for indole-3-acetic acid (IAA) degradation and signal interference. We determine the crystal structures and binding properties of the operon’s MarR-family repressor with IAA and other auxins. We identify auxin-degradation operons across the bacterial tree of life and define two distinct types based on gene content and metabolic products: iac-like and iad-like. We solve the structures of MarRs from representatives of each auxin degradation operon type, establishing that each have distinct IAA binding pockets. Comparison of representative IAA degrading strains from diverse bacterial genera show that while all degrade IAA, only strains containing iad-like auxin degrading operons interfere with auxin signaling in a complex synthetic community context. This suggests that iad-like operon containing strains, including Variovorax species, play a key ecological role in modulating auxins in the plant microbiome.
Project description:Streptococcus pneumoniae D39 AdcR (adhesion competence repressor) is the first metal-sensing member of the MarR (multiple antibiotic resistance repressor) family to be characterized. Expression profiling of a ∆adcR strain grown in liquid culture under microaerobic conditions revealed that transcript amounts for 13 genes were up-regulated relative to the wild-type strain, among them adcR, adcCBA, encoding a high affinity ABC uptake system for zinc, and genes encoding cell-surface zinc-binding pneumococcal histidine triad (pht) and adcII (lmb, laminin binding) proteins. Down-regulated transcripts included those encoding two putative zinc-containing alcohol dehydrogenases.
Project description:Streptococcus pneumoniae D39 AdcR (adhesion competence repressor) is the first metal-sensing member of the MarR (multiple antibiotic resistance repressor) family to be characterized. Expression profiling of a âadcR strain grown in liquid culture under microaerobic conditions revealed that transcript amounts for 13 genes were up-regulated relative to the wild-type strain, among them adcR, adcCBA, encoding a high affinity ABC uptake system for zinc, and genes encoding cell-surface zinc-binding pneumococcal histidine triad (pht) and adcII (lmb, laminin binding) proteins. Down-regulated transcripts included those encoding two putative zinc-containing alcohol dehydrogenases. Bacterial strains were grown exponentially in rich (BHI) media at 37C and an atmosphere of 5% CO2 to OD620~0.2, and were processed as described in the related Sample records. Samples were collected from three independent biological replicates and included one dye swap. Data were normalized using the Lowess (block) method without background subtraction. Changes in relative transcript amounts of positive or negative 2-fold with Bayesian P value of <0.001 were considered significant, and were included as supplementary material for the accompanying manuscript (The metalloregulatory site in Streptococcus pneumoniae AdcR, a zinc-activated MarR-family repressor; Reyes-Caballero, H. et al, manuscript in preparation).
Project description:The experiment contains ChIP-seq data for Enterotoxigenic Escherichia coli strain H10407 transformed with plasmids pAMNF (encoding an N-terminal MarR-3xFLAG fusion) or pAMNM (encoding an N-terminal MarR-8xmyc fusion). The cells was cultured at 37 degrees in LB medium and crosslinked with 1 % (v/v) formaldehyde. After sonication, to break open cells and fragment DNA, immunoprecipitations were done using an anti-FLAG antibody (i.e. the strain encoding the MarR-8xmyc fusion was used as a control). Libraries were prepared using DNA remaining after immunoprecipitation.