[Seminar] Identification of novel regulators of virulence in Erwinia carotovora

Title: Identification of novel regulators of virulence in Erwinia carotovora

Speaker: Filipe Vieira

Affiliation: Bacterial Signalling Lab - IGC

Abstract:

Erwinia carotovora (strain Ecc15) is a phytopathogen used as a model of bacterial oral infection in Drosophila melanogaster, which can induce a systemic immune response. The Erwinia virulence factor, Evf, is the major determinant for Ecc15 infection of the insect gut. However, the factors involved in the regulation of evf expression are not known. Given that in the Erwinia genus quorum sensing regulates pectolytic enzymes, the major virulence factors necessary to infect plants, we asked if Evf is also regulated by quorum sensing. We show that transcription of evf is regulated by the acyl-homoserine lactone (AHL) synthase gene expI, via the AHL receptors expR1 and expR2. Moreover, we show that the GacS/A two-component system (GAC) is also partially required for the activation of evf expression. However, through the profile of evf expression, we found that even if regulated by the same signaling networks, additional evf regulators play a role in the expression of this host-specific virulence factor. To identify those regulators, I performed a genetic screen using a reporter fusion for the expression of evf. From a library of 4800 mutants, I have selected and identified 45 mutants with lower and higher levels of evf expression when compared to the wild-type stain (WT), which I am currently characterizing. Due to the small size of the library, I also performed an RNAseq experiment to compare the genetic profile of the quorum sensing and the GAC system mutants with the WT strain. From the RNAseq data I identified 10 genes that are potential candidates for the unknown mechanisms regulating evf expression. Using this two experimental approaches, I expect to identify genes involved in the different levels of regulation observed for the different host specific virulence factors, which will allow a better understanding of how bacteria that infect multiple hosts maximize their fitness during transition between hosts.

Keywords:  Quorum sensing; Host-microbe Interactions; Infection; Regulation of Virulence