Identification and expression profiling of c-di-GMP signaling genes in the probiotic strain Escherichia coli Nissle 1917 during adhesion to the intestinal epithelial cells

Abstract

Cyclic-di-GMP (c-di-GMP) is a ubiquitous signaling molecule in many microorganisms that orchestrates genetic regulation during the transition between a sessile and motile lifestyle. The intracellular levels of c-di-GMP are stringently monitored by two enzymes, diguanylate cyclases (DGCs) consisting of GGDEF domain and phosphodiesterases (PDEs) with EAL or HD-GYP domain. This study scanned the probiotic strain Escherichia coli Nissle 1917 (EcN) genome for genes encoding for GGDEF and EAL domain-containing proteins. A total of 30 genes coding for proteins with canonical GGDEF, EAL, or both domains were identified. The expression of these genes in EcN during host intestinal cell colonization is yet to be characterized. Herein, the transcript levels of the 30 predicted genes implicated in c-di-GMP metabolism were analyzed in EcN during in vitro colonization of intestinal epithelial cells, Caco-2. The expression of two genes, dgcZ and sfaY, which play a vital role in the initial attachment to the cell surface and stress response, was highly up-regulated in EcN after 2 h of incubation with Caco-2 cells. Further, an affinity pull-down assay identified 53 c-di-GMP binding proteins. The in-depth genetic characterization will provide further insights into the c-di-GMP-mediated regulatory mechanisms during host colonization by the probiotic strains.

Funding

Science and Engineering Research Board (IN),(File No. PDF/2019/002852)