Tetrapisispora phaffii killer toxin is a highly specific β-glucanase that disrupts the integrity of the yeast cell wall

Francesca Comitini,Ilaria Mannazzu,Maurizio Ciani

doi:10.1186/1475-2859-8-55

Francesca Comitini, Ilaria Mannazzu + Show 1 more

Open Access

https://doi.org/10.1186/1475-2859-8-55

Copy DOI

Abstract

BackgroundKiller yeasts have been used to combat contaminating wild yeasts in food, to control pathogenic fungi in plants, and in the medical field, to develop novel antimycotics for the treatment of human and animal fungal infections. Among these killer yeasts, Tetrapisispora phaffii (formerly known as Kluyveromyces phaffii) secretes a glycoprotein known as Kpkt that is lethal to spoilage yeasts under winemaking conditions. In the present study, the mode of action of Kpkt, and the specific damage produced by this toxin on sensitive yeasts is investigated.ResultsThe use of castanospermine, a β-glucanase inhibitor, demonstrated that β-glucanase activity is essential for the Kpkt killer activity in vivo. Accordingly, Kpkt has no killer activity on either sensitive yeast spheroplasts or whole sensitive cells in the presence of isosmothic medium (0.8 molar sorbitol). Kpkt induces ultrastructural modifications in the cell wall of sensitive strains, as shown by confocal microscopy, laser-scanning electron microscopy, and atomic force microscopy. The Kpkt killer action is mediated by the glucidic portion of the toxin. This, in turn, appears to be involved both in the stronger cytocidal activity and in the selectivity for the sensitive strain shown by Kpkt compared to laminarinase.ConclusionCollectively, these data indicate that the mode of action of Kpkt is directed towards the disruption of cell-wall integrity, and that this is mediated by a highly specific β-glucanase activity. In this, Kpkt differs from other microbial β-glucanases that do not show killer activities.

Highlights

Killer yeasts have been used to combat contaminating wild yeasts in food, to control pathogenic fungi in plants, and in the medical field, to develop novel antimycotics for the treatment of human and animal fungal infections
Collectively, these data indicate that the mode of action of Kpkt is directed towards the disruption of cell-wall integrity, and that this is mediated by a highly specific -glucanase activity
Killer yeasts have been used to combat contaminating wild yeasts in food, and to control pathogenic fungi in plants [9,10,11]. These yeasts have been used in the development of novel antimycotics for the treatment of human and animal fungal infections [1,12,13] and in the biotyping of pathogenic yeasts and yeast-like fungi [14,15,16]

Summary

Introduction

Killer yeasts have been used to combat contaminating wild yeasts in food, to control pathogenic fungi in plants, and in the medical field, to develop novel antimycotics for the treatment of human and animal fungal infections. Among these killer yeasts, Tetrapisispora phaffii (formerly known as Kluyveromyces phaffii) secretes a glycoprotein known as Kpkt that is lethal to spoilage yeasts under winemaking conditions. It is known that under competitive conditions, the killer phenomenon offers a considerable advantage to these yeast strains against other sensitive microbial cells in their ecological niches This advantage has a basic and applied significance, and killer yeasts and their toxins have found several applications. The Kluyveromyces phaffii (recently reclassified as Tetrapisispora phaffii) [17] killer toxin, known as Kpkt and known to be active in the winemaking environment, has shown a wide cytocidal spectrum towards apiculate and other spoilage yeasts [18]

Methods

Results

Discussion

Conclusion