Microbe of the Week Monday: Hanseniaspora uvarum

With sincerest apologies to my co-terroirists and appreciative readers, I return to the wine blog, awaken from my slumber.  As Eric knows, I often succumb to deep sleeps, where my alter ego awakens and fights crime, saves maidens, and I become, Dream Warrior.

After a brief respite from the Wine World (I spent the summer gardening and hiking with kids), the harvest approaches, and I am drawn back, powerlessly, to the vines.  As a heat wave has settled in on the California Coast, growers and producers worry and hope, simultaneously.  Will the flavors and phenolics be ripe before the sugar spikes?

Looking for Hanseniaspora, Alisos Vineyard, Los Alamos, CA

And I, the Microbiologist, am pondering the populations of Hanseniaspora out there.  As I await my own little bins of Pinot Noir to arrive, I consider the question of the year: To inoculate, or to allow spontaneous ferment.

This is a popular question these days, so let me focus on a little critter with two names.  The French enologist Emile Peynaud suggested that perhaps 95% of the wild yeast present on the skin of a grape in the vineyard, is an apiculate (pointy ended) yeast named Hanseniaspora uvarum.  This pointy-ended yeast is seen in this photo sourced from my new favorite website, http://www.mycobank.org.

Hanseniaspora uvarum

This is what microbiologists call the anamorph form.  This means, the yeasts are making new yeasts by budding, which you can clearly see here.

If these yeasts were to make little saturn shaped spores, they would be called by their teleomorph name, Kloeckera apiculata.

So what?  Why does this matter?  Because these guys predominate the topographical surface of a grape.  When we harvest next week, and smash up these globes of goodness, this yeast will eat sugar and make nail polish remover.  If there are enough Saccharomyces around, (our Odysseus from previous post) he will essentially slay these foul-smelling pointy-yeasts, with his ethanol production of course.

But if there isn’t enough round shaped yeast, and we don’t intervene, Hanseniaspora will win.  He will marry Penelope, he will cause a stuck fermentaion, and he will cause our wine to taste like…I don’t even want to go there.

Stay Tuned,

Michael the Microbiologist