TheAzotobacter vinelandiiAlgU Regulon During Vegetative Growth and Encysting Conditions: A Proteomic Approach

Abstract

AbstractIn thePseduomonadaceafamily, the extracytoplasmic function sigma factor AlgU is crucial to withstand adverse conditions.Azotobacter vinelandii,a closed relative ofPseudomonas aeruginosa, has been a model for cellular differentiation in Gram-negative bacteria since it forms desiccation-resistant cysts. Previous work demonstrated the essential role of AlgU to withstand oxidative stress and onA. vinelandiidifferentiation, particularly for the positive control of alginate production. In this study, the AlgU regulon was dissected by a proteomic approach under vegetative growing conditions and upon encystment induction. Our results revealed several molecular targets that explained the requirement of this sigma factor during oxidative stress and extended its role in alginate production. Furthermore, we demonstrate that AlgU was necessary to produce alkyl resorcinols, a type of aromatic lipids that conform the cell membrane of the differentiated cell. AlgU was also found to positively regulate stress resistance proteins such as OsmC, LEA-1, or proteins involved in trehalose synthesis. A position-specific scoring-matrix (PSSM) was generated based on the consensus sequence recognized by AlgU inP. aeruginosa, which allowed the identification of direct AlgU targets in theA. vinelandiigenome. This work further expands our knowledge about the function of the ECF sigma factor AlgU inA. vinelandiiand contributes to explains its key regulatory role under adverse conditions.