A glimpse into the disease biology of Pantoea stewartii comes from early biochemical and ultra-structural studies of the organism in culture and in the infected maize tissues. The promoter region of esaR features a wellconserved lux box-like element, the esaR box, which spans a putative -10 hexameric σ70 promoter element. The authors focused initially on this promoter to define the functional role of EsaR as a transcription factor and DNA-binding protein. EsaR showed functional attributes that were essentially the reverse from that of the LuxR and TraR functional paradigms and other orthologous proteins that are acyl homoserine lactone (AHL)-dependent quorum-sensing activators. The observation that P. stewartii expresses the major EPSST virulence factor in a cell-density-dependent manner suggests a key role for the EsaI/EsaR quorum-sensing system in managing the transition between distinct phases of bacterial/biofilm development, which may be key to pathogen fitness during host colonization. In addition, other surface localized functions will be characterized to identify components that initiate the contact between the bacterium and the xylem wall, as seen in infections with the AHL mutant strain ESN51. Finally, it might be of interest to know that P. stewartii was initially selected as an experimental organism for quorum-sensing control because of its capacity to synthesize high amounts of AHL.