Identification of the main proteins secreted byKluyveromyces marxianusand their possible roles in antagonistic activity against fungi

Abstract

Lytic enzymes secreted by Kluyveromyces marxianus can lyse Saccharomyces cerevisiae cells. Their ability to hydrolyze yeast cell walls can be used in biotechnological applications, such as the production of glucans and protoplasts, as well as a biological control agent against plant pathogenic fungi. Herein, 27 proteins secreted by K. marxianus were identified by mass spectrometry analyses. Importantly, 14 out of the 27 proteins were classified as hydrolases. Indeed, the enzyme extract secreted by K. marxianus caused damage to S. cerevisiae cells and reduced yeast cell viability. Moreover, K marxianus inhibited spore germination and mycelial growth of the phytopathogenic fungus Botrytis cinerea in simultaneous co-cultivation assays. We suggest that this inhibition may be partially related to the yeast's ability to secrete lytic enzymes. Consistent with the in vitro antagonistic tests, K. marxianus was able to protect strawberry fruits inoculated with B. cinerea. Therefore, these findings suggest that K. marxianus possesses potential as a biocontrol agent against strawberry gray mold during the postharvest stage and may also have potential against other phytopathogenic fungi by means of its lytic enzymatic arsenal.

Molecular Basis of Yeasts Antimicrobial Activity—Developing Innovative Strategies for Biomedicine and Biocontrol

“…After internalization, the trimer is destabilized by breaking the disulfide bonds, the γ-subunit degrades tRNA, thus blocking the translation process, while the α-subunit enters inside the nucleus where it determines the repression of the CDC35 gene transcription, causing cellular arrest in the G1 phase of the cell cycle. When the zymocine interacts with a Candida cell, besides the previously described mechanism, the chitinase domain of the α-subunit directly interacts with the cell wall, causing its destabilization [38][39][40] (Figure 3). K. wickerhamii is a species basically isolated from various sources, such as spontaneously fermented dairy products from tropical areas and from grape must [41].…”