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

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.

Identification and characterization of a phase-variable element that regulates the autotransporter UpaE in uropathogenicEscherichia coli

“…To assess the functionality of UpaE in isolation, we utilized a plasmid based overexpression system it the E. coli K-12 background strain MS427 (48). MS427 has a mutation in the Ag43-encoding flu gene rendering it unable to facilitate biofilm formation or self-aggregation, and has previously been used successfully to probe the function of other autotransporters (20, 48–53). Immunoblots of whole cell lysates generated from MS427 transformed with a UpaE expression plasmid using a polyclonal anti-serum raised to a UpaE-MBP fusion protein showed a band consistent with the 271kDa predicted molecular weight of UpaE (Fig.…”

“…Immunofluoresence microscopy was performed essentially as previously described (53). Overnight cultures supplemented with the appropriate antibiotics and 1mM of IPTG were fixed to an OD 600 of 0.4, spotted onto a glass slide and allowed to dry.…”

The inverse autotransporters of Yersinia ruckeri, YrInv and YrIlm, contribute to biofilm formation and virulence

“…A similar structure was recently described for Y. enterocolitica (Lenchenko et al ., 2019). Many IATs from other organisms, particularly E. coli and the fish pathogen E. tarda , have been implicated in biofilm formation (Nesta et al ., 2012; Dong et al ., 2013; Martinez‐Gil et al ., 2017; Goh et al ., 2019). Therefore, we also investigated the role of the two Y. ruckeri IATs in our biofilm model.…”

“…YeeJ is a very large protein (2358 amino acids). Overexpression of YeeJ in E. coli MG1655 significantly increased the biofilm formation compared to the WT E. coli MG1655 strain (Nesta et al ., 2012; Martinez‐Gil et al ., 2017). Bioinformatics analysis showed that YeeJ, like other IATs, contains a LysM domain, which binds to peptidoglycan and stabilizes the proteins as shown previously for another E. coli IAT, Intimin (Leo et al ., 2015).…”

“…The expression of YrInv and YrIlm is regulated by environmental factors such as temperature, osmolarity, iron availability as well as the presence of nutrients (Wrobel et al ., 2017). Many IATs are involved in biofilm formation, such as FdeC, IatC and YeeJ from E. coli , and EtInvA from Edwardsiella tarda (Nesta et al ., 2012; Dong et al ., 2013; Martinez‐Gil et al ., 2017; Goh et al ., 2019). We therefore hypothesized that YrInv and YrIlm may play a role in biofilm formation and virulence of Y. ruckeri .…”