Background:

The sugar concentration gradient of the nectar-honey continuum varies from low in nectar to high concentration in honey. Variation in sugar concentration is a gradient determining yeast growth and leading to its ecological niche specialization.

Objective:

Evaluate the effect of a sugar concentration gradient on the growth kinetics and cell size of yeasts isolated from the floral nectar and honey of Melipona beecheii.

Methods:

Four strains identified as Metschnikowia koreensis and Sympodiomycopsis paphiopedili, isolated from floral nectar, and Starmerella apicola and Starmerella apicola 2, isolated from the honey of Melipona beecheii were grown in artificial media with a gradient of 2, 10, 20, 40, and 60 % glucose. We evaluated cell density, growth, and cell size in each strain.

Results and Conclusions:

Strains isolated from honey had high growth rates at the highest glucose concentrations, while strains isolated from floral nectar grew best at low concentrations. In addition, cell size decreased as glucose concentration increased in all yeasts. Thus, the data support the hypothesis that sugar concentration gradient is an ecological filter that modifies the growth and morphology of yeasts associated with flowers and honey and leads to niche specialization in yeasts that colonize plant-bee environments.

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