Every day, the pastry chef at Chanterelle, Kate Zuckerman, feeds her pet, which has lived in the kitchen of the TriBeCa restaurant for eight years. It’s not a dog or a cat that Ms. Zuckerman cares for, but a starter — the live culture she uses as a natural leavening agent when she bakes the daily bread for the restaurant.

Ms. Zuckerman could use store-bought yeast instead, but she’s convinced her bread wouldn’t have the complex, slightly sour flavor that naturally leavened breads tend to have. While the kind of dry yeast that is sold in the supermarket in foil packets is perfectly good for making the lovely pan and peasant loaves I recently learned to bake in a three-part class on “Techniques of Bread” at New York’s Institute of Culinary Education, natural starters are the key to artisanal bread that has just the right balance of acidity, sweetness, chewiness and crispness; a crackling crust that makes a noise when you break it; and a texture that is solid, but not too dense.

“Once you create a successful starter you become attached to it,” Ms. Zuckerman said. “You can always let it slow down in the refrigerator for a week or two and then revive it with multiple feedings a day.”

As long as she feeds her starter, or wild yeast, it can be used to leaven bread in perpetuity. If she stops giving it the flour and water it needs, the active cultures that cause the dough to rise would die after a few days.

A starter is basically dough, but because you keep adding more flour and water to it, and because fermentation causes it to rise and increase in volume, bread bakers usually keep some and throw the rest away. It’s common practice among bakers to share their winning starters with friends. “For some people, there is some romance to starters that are handed down from a great-grandmother or father,” the owner of Acme Bakery, which has locations in San Francisco and Berkeley, Calif., Steve Sullivan, said.

While Mr. Sullivan doesn’t personally put much stock in keeping track of the age of his starter, as some people and commercial bakeries do, he does respect the sentiment. “It means something that people have been paying attention, and whatever care is lavished upon it is going to have a beneficial effect,” he said. “But it’s more of a human cultural thing than a biological culture thing.” But even if I could convince Mr. Sullivan to share his sourdough starter with me, the bread I baked with it in New York City wouldn’t taste like San Francisco sourdough, no matter how proficient a baker I might become. “Why not?” I asked chef Nick Malgieri, who devised the curriculum at the Institute of Culinary Education.

“Starters are composed of different kinds of organisms,” Mr. Malgieri explained, noting that these bacteria contribute to the flavor of the baked bread. So even if you bring a starter to New York from Northern California, over the course of using it, the makeup will change as certain bacterial strains thrive in set environments.

But New York starters can have their own cachet, as Ms. Zuckerman knows, and even avid home bread bakers can make their own. A private tutor and Brooklyn resident, Alexander Auritt taught himself to make artisanal bread based on what he read in “Nancy Silverton’s Breads from the La Brea Bakery: Recipes for the Connoisseur” (Villard). He began to make his own starter: mixing flour and water into a paste, letting it proof in a warm place, then storing it in the refrigerator to allow the flavor to develop. (Some home bakers add sugar or grapes to the mixture of flour and water to encourage fermentation.)

Taking care of your starter doesn’t actually take that much actual time, Mr. Auritt said. “It’s about structuring your day so you can feed it two or three times a day for three days before you use it,” he said.

Mr. Auritt’s father even helped care for the hungry sourdough starter by shipping his son a 30-pound box of unbleached King Arthur bread flour.

It just may well be the perfect New York pet.