4-Hydroxy-3-Methyl-2-Alkenylquinoline Disrupts Temporospatial Control of Flagellar Assembly and Induces Transcriptomic Remodeling in Bacillus subtilis Consistent with a Short-Circuiting of the Spo0A Phosphorelay.

4-hydroxy-3-methyl-2-alkenylquinolines (HMAQs) belong to an emerging sub-class of naturally synthesized alkaloids with several prominent biological properties. HMAQ-7 is a novel variant recently identified in Burkholderia contaminans MS14 which was previously shown to impede normal cellular behaviors in Bacillus subtilis, including multiple colonization phenotypes such as motility, pellicle formation, and sporulation. While the list of biological and chemical characteristics among HMAQ's and related molecules is extensive, the mechanistic basis of these responses has been far more elusive. Using a combination of RNA-seq and bioinformatics, we have determined that several of the physiological defects induced by HMAQ-7 are strongly correlated with alterations in systems related to phospho-transduction. Specifically, HMAQ-7 augments gene expression in elements associated with late stationary phase growth, including those involved in phosphate assimilation and regulation of the spo0A phosphorelay. We also note that HMAQ-7 promotes dysregulated transcription of flagellar assembly genes which would normally be downregulated during late stationary phase. This study constitutes one of the first extensive investigations into an HMAQ's mode of action, providing vital insight into the ecological dynamics between B. contaminans and B. subtilis.