Ethanol stimulates trehalose production through a SpoT-DksA-AlgU dependent pathway in Pseudomonas aeruginosa

• Published in: bioRxiv
• Main Authors: Harty, Colleen E, Martins, Dorival, Doing, Georgia, Mould, Dallas L, Clay, Michelle E, Nguyen, Dao, Hogan, Deborah A
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 18.01.2019
• Subjects: Cell culture; Cell density; DNA-directed RNA polymerase; Ethanol; Gene expression; Inoculation; Osmotic stress; Proteolysis; Pseudomonas aeruginosa; RNA polymerase; Sigma factor; Transcription; Trehalose
• DOI: 10.1101/523126

Pseudomonas aeruginosa frequently resides among ethanol-producing microbes, and thus its response to microbially-produced concentrations of ethanol is relevant to understanding its biology. Transcriptome analysis found that the genes involved in trehalose metabolism were induced by ethanol, and levels of intracellular trehalose increased significantly upon growth with ethanol. The increase in trehalose was dependent on the TreYZ pathway, and not other trehalose metabolic enzymes TreS or TreA. The sigma factor AlgU (AlgT), a homolog of RpoE in other species, was required for the induction of the treZ gene and trehalose levels, but induction was not controlled by the well-characterized proteolysis of its antisigma factor MucA. Growth with ethanol led to increased (p)ppGpp, synthesized by SpoT, and genetic data suggest that increased (p)ppGpp stimulates AlgU-dependent transcription of treZ and other AlgU-regulated genes through DksA, an RNA polymerase binding protein. Ethanol stimulation of trehalose also required acylhomoserine lactone (AHL)-mediated quorum sensing (QS), as induction was not observed in a ΔlasRΔrhlR strain. Osmotic stress conferred by high salt is known to activate AlgU and TreYZ-dependent trehalose production, and we show that (p)ppGpp, DksA, and AHL-quorum sensing modulated this response. A network analysis of publicly available P. aeruginosa transcriptome datasets using eADAGE provides strong support our model that treZ and group of co-regulated genes are influenced by both AlgU and AHL-mediated QS. Ethanol, though added at the time of culture inoculation, only stimulated treZ transcript levels and trehalose production in post-exponential phase cultures, consistent with a model in which growth and cell density cues are integrated into the response to ethanol.