Ecotin and LamB in Escherichia coli influence the susceptibility to Type VI secretion-mediated interbacterial competition and killing by Vibrio cholerae

Si Lhyam Myint,Nikola Zlatkov,Kyaw Min Aung,Eric Toh,Annika Sjöström,Aftab Nadeem,Marylise Duperthuy,Bernt Eric Uhlin,Sun Nyunt Wai

doi:10.1016/j.bbagen.2021.129912

Si Lhyam Myint, Nikola Zlatkov + Show 7 more

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https://doi.org/10.1016/j.bbagen.2021.129912

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Journal: BBA - General Subjects	Publication Date: Apr 20, 2021
Citations: 7	License type: cc-by

Affiliation: Umeå University

Abstract

BackgroundA prevailing action of the Type VI secretion system (T6SS) in several Gram-negative bacterial species is inter-bacterial competition. In the past several years, many effectors of T6SS were identified in different bacterial species and their involvement in inter-bacterial interactions were described. However, possible defence mechanisms against T6SS attack among prey bacteria were not well clarified yet. MethodsEscherichia coli was assessed for susceptibility to T6SS-mediated killing by Vibrio cholerae. TheT6SS-mediated bacterial killing assays were performed in absence or presence of different protease inhibitors and with different mutant E. coli strains. Expression levels of selected proteins were monitored using SDS-PAGE and immunoblot analyses. ResultsThe T6SS-mediated killing of E. coli by V. cholerae was partly blocked when the serine protease inhibitor Pefabloc was present. E. coli lacking the periplasmic protease inhibitor Ecotin showed enhanced susceptibility to killing by V. cholerae. Mutations affecting E. coli membrane stability also caused increased susceptibility to killing by V. cholerae. E. coli lacking the maltodextrin porin protein LamB showed reduced susceptibility to killing by V. cholerae whereas E. coli with induced high levels of LamB showed reduced survival in inter-bacterial competition. ConclusionsOur study identified two proteins in E. coli, the intrinsic protease inhibitor Ecotin and the outer membrane porin LamB, that influenced E. coli susceptibility to T6SS-mediated killing by V. cholerae. General significanceWe envision that it is feasible to explore these findings to target and modulate their expression to obtain desired changes in inter-bacterial competition in vivo, e.g. in the gastrointestinal microbiome.

Highlights

Bacteria employ various protein secretion systems to interact with host organisms, adversary bacteria, and the environment
To investigate if protease inhibitors can inhibit the activity of the T6SS of V. cholerae, T6SS-mediated bacterial killing assay was per formed as described in Materials and Methods using the wild type V. cholerae strain V52 and the ΔvasK mutant as predator bacteria, and the wild type E. coli strain C600 as a prey bacterium in absence or in presence of protease inhibitors
To further test if the altered susceptibility was due to the LamB protein per se, and not merely resulting from some other induced factor or the inducer maltose, we introduced a plasmid har bouring the lamb+ gene into the E. coli strains C600, MC4100, MG1655 and the C600ΔlamB mutant and compared the susceptibility to V. cholerae killing of these E. coli strains in comparison with vector controls

Summary

Introduction

Bacteria employ various protein secretion systems to interact with host organisms, adversary bacteria, and the environment. In the past several years, using proteomic [7], genetic [8], and bio informatic analyses [9], the effectors of T6SS were identified in different bacterial species and their important roles in inter-bacterial interactions were described. A prevailing action of the Type VI secretion system (T6SS) in several Gram-negative bacterial species is inter-bacterial competition. In the past several years, many effectors of T6SS were identified in different bacterial species and their involvement in inter-bacterial interactions were described. E. coli lacking the maltodextrin porin protein LamB showed reduced susceptibility to killing by V. cholerae whereas E. coli with induced high levels of LamB showed reduced survival in inter-bacterial competition. Conclusions: Our study identified two proteins in E. coli, the intrinsic protease inhibitor Ecotin and the outer membrane porin LamB, that influenced E. coli susceptibility to T6SS-mediated killing by V. cholerae. General significance: We envision that it is feasible to explore these findings to target and modulate their expression to obtain desired changes in inter-bacterial competition in vivo, e.g. in the gastrointestinal microbiome

Methods

Results

Conclusion