Molecular and phenotypical diversities of autochthonous
oenological Saccharomyces cerevisiae strains from Lebanon.
Diversités moléculaire et phénotypique de souches autochtones oenologiques de Saccharomyces cerevisiae isolées au Liban.
Résumé
We explored in this study the biodiversity of the fermenting indigenous Lebanese flora
of Saccharomyces cerevisiae by collecting samples of natural fermentations of grape musts
from various localities dispersed within the Lebanese territory. A great molecular diversity of
the Lebanese flora was found in the natural fermentations, as well as in the wineries as a
whole and between different geographic localities. However, cases of dominance and
perenniallity were also recorded in wineries. Besides, fermentations in the same wineries
seemed to involve lineages of related strains. Relatedness of strains was also seen in narrow
geographical areas while it was lost as the areas enlarged. Despite its diversity, the Lebanese
flora could nevertheless be interrelated, which property was observed when this flora was
compared to other oenological floras of diverse origins. Finally, it seemed that the effect of
the thriving media was greater on the lineages of fermenting floras than the effect of the
geographical distance.
We also evaluated the usefulness of the molecular typing methods used for assessing the
biodiversity of the S. cerevisiae floras. Two of them, interdelta fingerprinting and
microsatellites analysis, were previously developed, while we tested a new method, the
MLST. The first two methods were very useful for typing due to the great variability of their
markers and thus to their great discriminatory power, while MLST showed a lower
discriminatory power. But our MLST scheme could probably be improved by using more
variable loci. MLST was nonetheless more useful in inferring strains relatedness, especially
for poorly related isolates.
We further examined the phenotypic diversity that accompanies the molecular one in
order to initiate a selection scheme for some oenological strains and also to verify the
correspondence between the molecular and the phenotypic diversity. The studied strains of S.
cerevisiae presented different fermenting capacities which could be exploited to push further
the selection scheme for potential commercial uses, in particular in the Lebanese winemaking
industry. On the other hand, a certain congruence between the molecular and the phenotypic
diversities was observed and it was mainly due to a correlation between high acetaldehyde
productions and particular molecular profiles. If this path is studied further, this congruence
might help predict acetaldehyde production for particular strains
of Saccharomyces cerevisiae by collecting samples of natural fermentations of grape musts
from various localities dispersed within the Lebanese territory. A great molecular diversity of
the Lebanese flora was found in the natural fermentations, as well as in the wineries as a
whole and between different geographic localities. However, cases of dominance and
perenniallity were also recorded in wineries. Besides, fermentations in the same wineries
seemed to involve lineages of related strains. Relatedness of strains was also seen in narrow
geographical areas while it was lost as the areas enlarged. Despite its diversity, the Lebanese
flora could nevertheless be interrelated, which property was observed when this flora was
compared to other oenological floras of diverse origins. Finally, it seemed that the effect of
the thriving media was greater on the lineages of fermenting floras than the effect of the
geographical distance.
We also evaluated the usefulness of the molecular typing methods used for assessing the
biodiversity of the S. cerevisiae floras. Two of them, interdelta fingerprinting and
microsatellites analysis, were previously developed, while we tested a new method, the
MLST. The first two methods were very useful for typing due to the great variability of their
markers and thus to their great discriminatory power, while MLST showed a lower
discriminatory power. But our MLST scheme could probably be improved by using more
variable loci. MLST was nonetheless more useful in inferring strains relatedness, especially
for poorly related isolates.
We further examined the phenotypic diversity that accompanies the molecular one in
order to initiate a selection scheme for some oenological strains and also to verify the
correspondence between the molecular and the phenotypic diversity. The studied strains of S.
cerevisiae presented different fermenting capacities which could be exploited to push further
the selection scheme for potential commercial uses, in particular in the Lebanese winemaking
industry. On the other hand, a certain congruence between the molecular and the phenotypic
diversities was observed and it was mainly due to a correlation between high acetaldehyde
productions and particular molecular profiles. If this path is studied further, this congruence
might help predict acetaldehyde production for particular strains
Nous avons exploré dans la présente étude la diversité de la flore fermentaire indigène libanaise de Saccharomyces cerevisiae en collectant des échantillons de moûts de raisins en cours de fermentations naturelles de diverses localités dispersées sur le territoire libanais. Une grande diversité moléculaire de la flore libanaise a été mise en évidence, que ce soit entre différentes localités géographiques, au sein des caves ou au sein des fermentations naturelles. En dépit de cette diversité, plusieurs cas de dominance et de pérennité de souches ont été observés dans les caves vinicoles où les fermentations semblent être conduites par des lignées de souches apparentées. Une telle parenté a aussi été observée dans des zones géographiques restreintes, mais plus la zone s'élargissait moins apparente était la parenté entre souches. La flore libanaise, en dépit de sa diversité, pourrait être dotée d'une certaine spécificité en comparaison aux autres flores vinicoles. L'influence du milieu de fermentation sur la parenté des isolats semble en outre plus importante que l'effet géographique. Nous avons aussi évalué les méthodes moléculaires utilisées pour l'exploration de la diversité ; deux méthodes déjà mises au point auparavant (amplifications de séquences entre deux éléments delta et de loci microsatellites) et une nouvelle méthode que nous avons testé, le MLST. Les deux premières méthodes se sont avérées très utiles pour le typage vu la grande variabilité de leurs marqueurs et par conséquent leur grande capacité de discrimination. Par contre le schéma MLST a montré une capacité de discrimination inférieure à celle des deux autres méthodes. Il pourrait néanmoins être amélioré par l'utilisation de loci plus variables. Mais contrairement aux deux autres méthodes, le MLST est apparu plus utile pour l'inférence des relations phylogéniques, particulièrement pour les souches peu apparentées. La diversité phénotypique accompagnant la diversité moléculaire a été examinée elle aussi en vue d'une potentielle sélection de souches et pour envisager son éventuelle congruence avec la diversité moléculaire. Les souches étudiées de S. cerevisiae ont présenté des capacités fermentaires différentes ce qui pourrait être exploité pour pousser la sélection entamée dans cette étude en vue de futures utilisations oenologiques, notamment dans l'industrie vinicole libanaise. La diversité phénotypique qui a accompagné la diversité moléculaire a montré une certaine congruence avec elle. Cette congruence a été particulièrement reliée à la production élevée d'acétaldéhyde de certains profils moléculaires et elle pourrait éventuellement aider à prédire la production d'acétaldéhyde pour certaines souches.
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