The ubiquitous plant pathogen Agrobacterium tumefaciens attaches efficiently to plant tissues and abiotic surfaces and can form complex biofilms. A genetic screen for mutants unable to form biofilms on PVC identified disruptions in a homologue of the exoR gene. ExoR is a predicted periplasmic protein, originally identified in Sinorhizobium meliloti, but widely conserved among alphaproteobacteria. Disruptions in the A. tumefaciens exoR gene result in severely compromised attachment to abiotic surfaces under static and flow conditions, and to plant tissues. These mutants are hypermucoid due to elevated production of the exopolysaccharide succinoglycan, via derepression of the exo genes that direct succinoglycan synthesis. In addition, exoR mutants have lost flagellar motility, do not synthesize detectable flagellin and are diminished in flagellar gene expression. The attachment deficiency is, however, complex and not solely attributable to succinoglycan overproduction or motility disruption. A. tumefaciens ExoR can function independently of the ChvG–ChvI two component system, implicated in ExoR-dependent regulation in S. meliloti. Mutations that suppress the exoR motility defect suggest a branched regulatory pathway controlling succinoglycan synthesis, motility and biofilm formation.

Background The response to the anticoagulant drug warfarin is greatly affected by genetic polymorphisms in the VKORC1 and CYP2C9 genes. Genotyping these polymorphisms has been shown to be important in reducing the time of the trial and error process for finding the maintenance dose of warfarin thus reducing the risk of adverse effects of the drug. Method We developed a real-time isothermal DNA amplification system for genotyping three single nucleotide polymorphisms (SNPs) that influence warfarin response. For each SNP, real-time isothermal Helicase Dependent Amplification (HDA) reactions were performed to amplify a DNA fragment containing the SNP. Amplicons were detected by fluorescently labeled allele specific probes during real-time HDA amplification. Results Fifty clinical samples were analyzed by the HDA-based method, generating a total of 150 results. Of these, 148 were consistent between the HDA-based assays and a reference method. The two samples with unresolved HDA-based test results were repeated and found to be consistent with the reference method. Conclusion The HDA-based assays demonstrated a clinically acceptable performance for genotyping the VKORC1 -1639G>A SNP and two SNPs (430C>T and 1075A>C) for the CYP2C9 enzyme (CYP2C9*2 and CYP2C9*3), all of which are relevant in warfarin pharmacogenentics.

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