YeeJ is an inverse autotransporter from Escherichia coli that binds to peptidoglycan and promotes biofilm formation

Marta Martinez-Gil,Kelvin G K Goh,Elze Rackaityte,Mark A Schembri,Christophe Beloin,Bianca Audrain,Chizuko Sakamoto,Makrina Totsika,Danilo G Moriel,Jean-Marc Ghigo

doi:10.1038/s41598-017-10902-0

Abstract

Escherichia coli is a commensal or pathogenic bacterium that can survive in diverse environments. Adhesion to surfaces is essential for E. coli colonization, and thus it is important to understand the molecular mechanisms that promote this process in different niches. Autotransporter proteins are a class of cell-surface factor used by E. coli for adherence. Here we characterized the regulation and function of YeeJ, a poorly studied but widespread representative from an emerging class of autotransporter proteins, the inverse autotransporters (IAT). We showed that the yeeJ gene is present in ~40% of 96 completely sequenced E. coli genomes and that YeeJ exists as two length variants, albeit with no detectable functional differences. We demonstrated that YeeJ promotes biofilm formation in different settings through exposition at the cell-surface. We also showed that YeeJ contains a LysM domain that interacts with peptidoglycan and thus assists its localization into the outer membrane. Additionally, we identified the Polynucleotide Phosphorylase PNPase as a repressor of yeeJ transcription. Overall, our work provides new insight into YeeJ as a member of the recently defined IAT class, and contributes to our understanding of how commensal and pathogenic E. coli colonise their environments.

Highlights

Escherichia coli is a versatile bacterium comprising both commensal and pathogenic strains found in intra- and extra-intestinal environments[1]
No significant difference was observed between the biofilms formed by strains expressing either YeeJ variant. These results demonstrate that YeeJ can promote biofilm formation when expressed in a recombinant E. coli K-12 strain, and that there is no difference between the ability of the two YeeJ variants to mediate biofilm formation under the conditions examined in these experiments
outer membrane vesicles (OMVs) are inherently enriched in surface exposed proteins[59], and we previously showed that ethylenediaminetetraacetic acid (EDTA)/heat-induced OMVs of uropathogenic E. coli are strongly enriched with OM and extracellular proteins[60, 61]

Summary

Introduction

Escherichia coli is a versatile bacterium comprising both commensal and pathogenic strains found in intra- and extra-intestinal environments[1]. Genomic analysis of the E. coli K-12 strain MG1655 revealed the presence of numerous genes encoding potentially cryptic adhesins, including AT proteins that contribute to attachment and colonization[9, 10]. We used the RExBAD cassette to place an arabinose inducible promoter upstream of putative adhesin-encoding genes in E. coli MG1655, and identified novel cryptic adhesins involved in biofilm formation that were not expressed under standard laboratory growth conditions[9]. This analysis identified YeeJ as an intimin-like protein involved in adhesion to different abiotic surfaces. This work enhances our understanding of YeeJ and its contribution to E. coli adhesion and biofilm formation

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