Characterization of cell density-regulated gene expression of the grass endophyte Azoarcus sp. BH72. Azoarcus sp.

Azoarcus sp. BH72 is able to communicate via cell density-dependent gene regulation. Here, the impact of cell-free conditioned culture supernatants, obtained from stationary phase Azoarcus wild type cultures, on gene expression was investigated determining changes in transcript profiles when early exponential aerobic cultures were incubated with cell-free culture supernatants for one and four hours. Bacterial communication via quorum sensing (QS) is involved in the regulation of several cellular mechanisms such as metabolic processes, microbe-host interactions or biofilm formation. The nitrogen-fixing model endophyte of grasses Azoarcus sp. strain BH72 shows density-dependent gene regulation in the absence of common hydrophobic autoinducers for pilA encoding the structural protein of type IV pili that are essential for plant colonization. Here, we used a transcriptomic approach to identify target genes differentially regulated under QS conditions in conditioned supernatants in comparison to standard growth conditions. Overall design: Analysis used RNA from the early exponential growth phase as control samples for comparison to the quorum-sensing condition samples taken at one hour and four hours after incubation with cell-free culture supernatants.