The effect of sugar concentration on yeast growth associated with floral nectar and honey

Abstract

Background: Floral nectar and honey vary in sugar concentration, from low concentration in nectar to high concentration in honey. Variation in sugar concentration is a gradient that determines yeast growth and can lead 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 honey of Melipona beecheii were grown in artificial media with a gradient of 2, 10, 20, 40 and 60% glucose. We evaluated culture density (cells / µL), growth parameters, 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. Cell size decreased as glucose concentration increased in all strains. The data supports 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.