Interplay between OmpA and RpoN Regulates Flagellar Synthesis in Stenotrophomonas maltophilia

Chun-Hsing Liao,Chun-Hsing Liao,Yi-Tsung Lin,Hsin-Hui Huang,Tsuey-Ching Yang,Li-Hua Li,Chia-Lun Chang

doi:10.3390/microorganisms9061216

Chun-Hsing Liao, Chun-Hsing Liao + Show 5 more

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https://doi.org/10.3390/microorganisms9061216

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Abstract

OmpA, which encodes outer membrane protein A (OmpA), is the most abundant transcript in Stenotrophomonas maltophilia based on transcriptome analyses. The functions of OmpA, including adhesion, biofilm formation, drug resistance, and immune response targets, have been reported in some microorganisms, but few functions are known in S. maltophilia. This study aimed to elucidate the relationship between OmpA and swimming motility in S. maltophilia. KJΔOmpA, an ompA mutant, displayed compromised swimming and failure of conjugation-mediated plasmid transportation. The hierarchical organization of flagella synthesis genes in S. maltophilia was established by referencing the Pseudomonas aeruginosa model and was confirmed using mutant construction, qRT-PCR, and functional assays. Distinct from the P. aeruginosa model, rpoN, rather than fleQ and fliA, was at the top of the flagellar regulatory cascade in S. maltophilia. To elucidate the underlying mechanism responsible for ΔompA-mediated swimming compromise, transcriptome analysis of KJ and KJΔOmpA was performed and revealed rpoN downregulation in KJΔOmpA as the key element. The involvement of rpoN in ΔompA-mediated swimming compromise was verified using rpoN complementation, qRT-PCR, and function assays. Collectively, OmpA, which contributes to bacterial conjugation and swimming, is a promising target for adjuvant design in S. maltophilia.

Highlights

Gram-negative bacteria are surrounded by two membranes, which confine the periplasmic space containing the peptidoglycan [1]
Transcriptome analysis of S. maltophilia KJ was performed in our recent study, and the results demonstrated that ompA (Smlt0955) has the greatest transcript abundance in logarithmically grown KJ cells [33]
The flagellum and swimming motility are well characterized in several Gram-negative bacteria, such as

Summary

Introduction

Gram-negative bacteria are surrounded by two membranes, which confine the periplasmic space containing the peptidoglycan [1]. This double membrane may be impenetrable to antibiotics, noxious agents, or other foreign compounds [2,3]. As much as 3% of the Gram-negative bacterial genome may encode outer membrane proteins (OMPs) [4]. Most of the integral membrane proteins of the OM assume a β-barrel architecture with long loops between the strands on the extracellular side and short loops on the periplasmic side. Β-barrel OMPs are classified into two major types, classical porins and slow porins, based on their physiological roles.

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