Ricardo Manuel Fernandes Santos, NOVA School of Sciences and Technology - University of Lisbon

FERNANDES-SANTOS(a,b,c,d,e), Ricardo; CASTILLO(f), Mariangie M.; CÂMARA(f,g), José S.; RODRÍGUEZ-COUSIÑO(h,i), Nieves; SANTOS(e), Conceição; SCHWARTZ(c), Jean-Marc; GONÇALVES(a,b), Paula; KOTTA-LOIZOU(d,j), Ioly (a) UCIBIO, Department of Life Sciences, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal (b) Associate Laboratory i4HB, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal (c) School of Biological Sciences, University of Manchester, Manchester, UK (d) Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, SW7 2AZ, UK (e) Department of Biology, LAQV-REQUIMTE, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal (f) CQM—Centro de Química da Madeira, Universidade da Madeira, Campus da Penteada, 9020-105 Funchal, Portugal (g) Departamento de Química, Faculdade de Ciências Exatas e Engenharia, Universidade da Madeira, Campus da Penteada, 9020-105 Funchal, Portugal (h) Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, Salamanca, Spain (i) Escuela Politécnica Superior de Zamora, Universidad de Salamanca, Salamanca, Spain (j) Department of Clinical, Pharmaceutical and Biological Science, School of Health, Medicine and Life Sciences, University of Hertfordshire, Hatfield, AL10 9AB, UK

Epidemiology, Evolution, and Diversity

Killer yeasts are infected with a double-stranded (ds)RNA virus that encodes a toxin (M virus) and a helper virus (L-A virus) belonging to the Totiviridae family. Previous studies have primarily focused on Saccharomyces cerevisiae and, more recently, Saccharomyces paradoxus, although other yeasts also exhibit killer phenotypes. While infection and immunity mechanisms have been investigated, they are not fully elucidated. The present project focuses on comparing the functional characteristics of known toxins and screening yeast populations for viral killer systems.

Each known toxin, K1, K2 and Klus derived from S. cerevisiae and K21/K66, K28, K45, K62 and K74 derived from S. paradoxus, exhibits a distinct pH range and optimum for maximal activity against sensitive S. cerevisiae 5X47. Across all toxins, pH 4.5 was found to be the most effective in killer assays and will be used for further oxidative stress assays and transcriptome profiling of toxin-exposed strains.

Among 12 S. cerevisiae strains originating from Madeira island (Portugal) and used in wine production, 11 exhibited killer activity. All killer strains produced the K2 toxin, but variations in the diameter of inhibition halos against the sensitive strains 5X47 and BY4741 suggest potential genetic differences in the host and/or the viruses. Phylogenetic studies are currently conducted to understand the population structure and dynamics of killer yeast systems in the geographically isolated Madeira.

These findings have significant implications for both science and biotechnology. By expanding the understanding of function and diversity in killer yeast systems, this research contributes to the broader study of microbial symbioses.