But that's because only San Francisco is home to a certain bacterium that bears its name– Lactobacillus sanfranciscensis.

Of course bread uses another microbe– the yeast that turns sugar into the air bubbles that lighten the loaf. For sourdough, though, local bacteria then add their secret ingredient. They eat up the yeast's waste and turn it into acid, making the bread San Francisco sour.

The bacteria also make the dough inhospitable for other microbes, keeping all that doughy goodness for the yeast and itself. The yeast and bacteria make such great partners because the yeast can't eat the sugar maltose, which the bacteria absolutely need.

San Franciscans have been noshing on this local concoction since at least the Gold Rush. Boudin Bakery first baked buns in 1849. Some bakeries even claim to have a "starter"– the bit of dough that contains yeast and bacteria– that's over a century old. They pinch off a piece of starter for every new loaf, and care for the dough with regular feedings of flour and water.

If you've got a favorite brand, chances are it's because of the unique mix of yeast and bacteria from that bakery. Other towns' sourdough will taste a little bit different because their bacteria aren't the San Francisco kind.

Want to whip up a loaf unique to your backyard? The Exploratorium has a recipe to make your own starter that will pick up local yeast and bacteria. Or if you prefer that authentic San Francisco flavor, buy the original.

For more on Lactobacillus sanfranciscensis, check out the Berkeley Science Review.

Amber Dance is the Quest Intern and a science communication student at UC Santa Cruz.

Amundsen-Scott South Pole Station

As the sun shines and the air warms in the Bay Area, take a moment to consider a place where it's always cold–the South Pole. Thanks to some local folk, we can get a taste of the science at the bottom of the earth without leaving balmy San Francisco.

Berkeley graduate student Michaelangelo D'Agostino blogs about his trip south for the Economist. D'Agostino chronicles the stages of his journey, from New Zealand to the station, and what day-to-day life is like at -24 degrees Celsius.

SF's own Exploratorium brings Antarctic scientists, live, to your computer monitor. In the webcasts, archived so you can watch any time,
scientists explain their research on everything from penguins and glaciers to neutrinos. The also have dispatches, updates from the scientists as they go about their work.

Amber Dance is the Quest Intern and a science communication student at UC Santa Cruz.

latitude: -90, longitude: 0

We scour the web and serve up the best of science, environment and nature content–from the Bay area and beyond–right to our readers.

Today's pick is from YouTube.

National Geographic, via YouTube, brings us the tale of Australia’s water-holding frog. This plucky amphibian rarely sees rain, so when it does, it slurps enough liquid to double its weight. Then it digs a hole and hides in a shell made of its own shed skin. It can hibernate for up to two years, until the rainy season comes 'round again and it's time to look for a mate.Supposedly aboriginals even dig up the frogs when they need a drink–just squeeze and you've got fresh water!Check out the video of this amphibious camel for more on its amazing adaptations:

http://www.youtube.com/watch?v=tuWo_kWMihs

Amber Dance is the Quest Intern and a science communication student at UC Santa Cruz.