Quantifying variation in the ability of yeasts to attract Drosophila melanogaster

Yeasts that invade and colonise fruit significantly enhance the volatile chemical diversity of this ecosystem. These modified bouquets are thought to be more attractive to Drosophila flies than the fruit alone, but the variance of attraction in natural yeast populations is uncharacterised. Here we investigate how a range of yeast isolates affect the attraction of female D. melanogaster to fruit in a simple two choice assay comparing yeast to sterile fruit. Of the 43 yeast isolates examined, 33 were attractive and seven repellent to the flies. The results of isolate-versus-isolate comparisons provided the same relative rankings. Attractiveness varied significantly by yeast, with the strongly fermenting Saccharomyces species generally being more attractive than the mostly respiring non-Saccharomyces species (P = 0.0035). Overall the habitat (fruit or other) from which the isolates were directly sampled did not explain attraction (P = 0.2352). However, yeasts isolated from fruit associated niches were more attractive than those from non-fruit associated niches (P = 0.0188) regardless of taxonomic positioning. These data suggest that while attractiveness is primarily correlated with phylogenetic status, the ability to attract Drosophila is a labile trait among yeasts that is potentially associated with those inhabiting fruit ecosystems. Preliminary analysis of the volatiles emitted by four yeast isolates in grape juice show the presence/absence of ethanol and acetic acid were not likely explanations for the observed variation in attraction. These data demonstrate variation among yeasts for their ability to attract Drosophila in a pattern that is consistent with the hypothesis that certain yeasts are manipulating fruit odours to mediate interactions with their Drosophila dispersal agent. © 2013 Palanca et al

Characterization of a versatile arylesterase from Lactobacillus plantarum active on wine esters

The gene lp-1002 from Lactobacillus plantarum WCFS1 encoding a putative lipase/esterase was cloned and overexpressed in Escherichia coli BL21(DE3). The purified Lp-1002 protein was biochemically characterized. Lp-1002 is an arylesterase which showed high hydrolytic activity on phenyl acetate. Although to a lesser extent, Lp-1002 also hydrolyzed most of the esters assayed including relevant wine aroma compounds. Importantly, Lp-1002 exhibited hydrolytic activity at winemaking conditions, although optimal catalytic activity is observed at 40 °C and pH 5-7. The effect of wine compounds on Lp-1002 activity was assayed. From the compounds assayed (ethanol, sodium metabisulfite, and malic, tartaric, lactic and citric acids), only malic acid slightly inhibited Lp-1002 activity. Lp-1002 is the first arylesterase described in a wine lactic acid bacteria and possessed suitable biochemical properties to be used during winemaking. © 2014 American Chemical Society.This work was financially supported by grants AGL2011-22745 and BFU2010-17929 (MINECO), S2009/AGR-1469 (ALIBIRD) (Comunidad de Madrid), and RM2012-00004 (INIA). M. Esteban-Torres is a recipient of a JAE predoctoral fellowship from the CSIC.Peer Reviewe