It turns out long-living bacteria in salt crystals beneath Death Valley require very little sustenance.

Imagine you were trapped in a room for weeks with nothing to eat but a single leaf of lettuce. Sound like a nightmare in crash dieting?

For microscopic bacteria holed up in ancient buried salt flats in California's Death Valley, that's life. In fact, according to a new study, the fasting bugs have been subsisting on just a few cells of algae for at least the past 34,000 years.

These aren't the oldest beings with an extremely small appetite. In fact, scientists claim to have discovered living bacteria huddled in salt deposits that date back 250 million years.

Such findings are controversial, not least because it's very easy to contaminate ancient samples with modern organisms. Scientists have also puzzled over just how anything could live that long. Do they go dormant? What, if anything, do they eat?

In this weird environment, algae is the stuff of life. Once encased in salt and buried, plant cells die out quickly, but as they break down nutrients leak out that bacteria can use. According to the team's calculations, a single algae cell can sustain one bacterium for a whopping 12 million years.

During that time, the bugs essentially go into suspended animation. They cease reproduction, movement, and shrink to a fraction of their normal size. The only thing they do, the team speculates, is sip at the salty nutrient soup and repair damage to their DNA that accrues over time.

The research was published in a recent issue of the journal, Geology.

"The algae discovery is very exciting, it makes each pocket of fluid a complete ecosystem," Robert Hazen of the Carnegie Institute of Washington said. "It suggests a way that microbes could be preserved for very long periods of time."

Hazen cautioned that experiments still need to be repeated to see whether bacteria have indeed survived for up to 250 million years in salty isolation. But the discovery increases the likelihood that extreme organisms could be found tucked away for millions of years all around Earth, and perhaps even other planets.