Serratia marcescens: Blowing Corneal Epithelial Cell Bubbles with GumB

摘要

Purpose : Serratia marcescens causes bacterial keratitis and contact lens associated complications yet its virulence factors are poorly understood. Previous studies have shown that another bacteria, Pseudomonas aeruginosa, induces outer membrane blebs in corneal cells through a type III secretion system. We observed that S. marcescens induced epithelial bleb formation in human corneal limbal epithelial cells (HCLE) and human keratinocytes in vitro, yet S. marcescens lacks a type III secretion system. The purpose of this study was to identify the mechanism by which S. marcescens causes epithelial cell bleb formation. Methods : A mariner transposon library of corneal keratitis isolate K904 was screened for mutations that inactivated the bacterial bleb induction in HCLE cells. Results : ~7,000 mutants were used to challenge HCLE layers and the challenged epithelial cells were examined microscopically. Of the tested mutants, 5 were defective in inducing bleb formation. Two of the Bleb- isolates had transposons that map to different loci in an uncharacterized gene in S. marcescens named gumB. A deletion mutation of the gumB gene was generated and the resulting mutant was defective in bleb formation. Complementation of the gumB open reading frame mutant confirmed the role of this gene in bleb induction. Other bleb-inducing defective bacteria had mutations in a type V secretion system. Expression of the type V system in Escherichia coli conferred the ability to induce blebs. Conclusions : This analysis identified a novel mechanism for inducing necrotic bleb formation in corneal cells: through a type V secretion system. Future studies to inhibit this mechanism may help reduce contact lens associated complications and keratitis associated vision loss. This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.