Phobalysin, a Small β-Pore-Forming Toxin of Photobacterium damselae subsp. damselae.

Martina Meyenburg,Claudia Neukirch,Amable J. Rivas,Klaus Boller,A. Camilli,Manuel L. Lemos,Gisela von Hoven,Carlos R. Osorio,Matthias Husmann,Qianqian Qin,Sabine Füser

doi:10.1128/iai.00277-15

Abstract

Photobacterium damselae subsp. damselae, an important pathogen of marine animals, may also cause septicemia or hyperaggressive necrotizing fasciitis in humans. We previously showed that hemolysin genes are critical for virulence of this organism in mice and fish. In the present study, we characterized the hlyA gene product, a putative small β-pore-forming toxin, and termed it phobalysin P (PhlyP), for "photobacterial lysin encoded on a plasmid." PhlyP formed stable oligomers and small membrane pores, causing efflux of K(+), with no significant leakage of lactate dehydrogenase but entry of vital dyes. The latter feature distinguished PhlyP from the related Vibrio cholerae cytolysin. Attack by PhlyP provoked a loss of cellular ATP, attenuated translation, and caused profound morphological changes in epithelial cells. In coculture experiments with epithelial cells, Photobacterium damselae subsp. damselae led to rapid hemolysin-dependent membrane permeabilization. Unexpectedly, hemolysins also promoted the association of P. damselae subsp. damselae with epithelial cells. The collective observations of this study suggest that membrane-damaging toxins commonly enhance bacterial adherence.

Highlights

Photobacterium damselae subsp. damselae, an important pathogen of marine animals, may cause septicemia or hyperaggressive necrotizing fasciitis in humans
We characterized the product of P. damselae subsp. damselae hlyApl and termed it “photobacterial lysin encoded on a plasmid”
To obtain experimental evidence that phobalysin P (PhlyP) is a small ␤-pore-forming toxin (PFT), we incubated ECPs from P. damselae subsp. damselae strain AR119 (⌬dly ⌬hlyAch; produces only HlyApl) with erythrocyte ghosts and separated firmly bound proteins by SDSPAGE

Summary

Introduction

Photobacterium damselae subsp. damselae, an important pathogen of marine animals, may cause septicemia or hyperaggressive necrotizing fasciitis in humans. We characterized the hlyA gene product, a putative small ␤-pore-forming toxin, and termed it phobalysin P (PhlyP), for “photobacterial lysin encoded on a plasmid.”. PhlyP formed stable oligomers and small membrane pores, causing efflux of K؉, with no significant leakage of lactate dehydrogenase but entry of vital dyes. PFTs may cause direct damage of target cells [18], promote escape from membrane-bound compartments [19, 20], or introduce virulence factors into the cytosol [21] (for recent reviews, see references 22 and 23). Damselae hlyApl and termed it “photobacterial lysin encoded on a plasmid” (phobalysin P [PhlyP]) This toxin exhibits distinct properties as well as features shared by other small ␤-PFTs, underscoring the diversity of these toxins. The results fuel the idea that hemolysins trigger complex stress responses, and they support an emerging role in bacterial adherence to target cells

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Conclusion