Terroir is a concept at the heart of French winemaking, but one so mysterious that the word has no English counterpart. It denotes the holistic combination of soil, geology, climate and local grape-growing practices that make each region’s wine unique.

There must be something to terroir, given that expert wine tasters can often identify the region from which a wine comes. But American wine growers have long expressed varying degrees of skepticism about this ineffable concept, some dismissing it as unfathomable mysticism and others regarding it as a shrewd marketing ploy to protect the cachet of French wines.

Now American researchers may have penetrated the veil that hides the landscape of terroir from clear view, at least in part. They have seized on a plausible aspect of terroir that can be scientifically measured — the fungi and bacteria that grow on the surface of the wine grape.

These microbes certainly affect the health of grapes as they grow — several of them adversely — and they are also incorporated into the must, the mashed grapes that are the starting material of winemaking. Several of the natural fungi that live on grapes have yeastlike properties, and they and other microbes could affect the metabolism of the ensuing fermentation. (Several species of microbes are available commercially for inoculation along with yeast into wine fermentations.)