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BIOLOGISTS are about to go bug hunting on a grand scale. By tricking bacteria into thinking they are still in their natural environment, they will be able to grow formerly elusive bugs in the laboratory, tapping into a goldmine of genetic information that could be used to make new drugs.

Enzymes isolated from microbes drove the revolution in genomics and molecular biology in the 1990s, with the result that bacteria are now a major source of industrial enzymes and new medicines. But we still know very little about most of the world鈥檚 bugs. Of the million or so species of different bacteria on Earth, only a few thousand have ever been isolated and grown in a lab. Most are known by sight only, and researchers have struggled to identify even a few snippets of their genes.

鈥淚magine an animal biologist studying jungle rainforests who has only been able to capture one mosquito,鈥� says Slava Epstein of Northeastern University in Boston. 鈥淏y comparison, that鈥檚 where we are.鈥�

The problem isn鈥檛 finding these so-called 鈥渦ncultivable鈥� bugs鈥攕ome are major players in the environment, for instance driving soil ecology. But no one has found the right stew of chemicals to get them to thrive outside their natural home.

Typically, researchers put bacteria collected from the wild directly on nutrient-rich gels in Petri dishes, then look for the growth of visible mounds of bacteria, or colonies. But that only works for a tiny minority of bugs. So Epstein and his colleagues Tammi Kaeberlein and Kim Lewis decided to make the bacteria feel more at home.

They isolated bacteria from beach sand and placed the bugs individually in a soft gel. The gel was then sealed in a permeable membrane, laid on top of the sand and covered with seawater. The gel and membrane allowed the bacteria to exchange nutrients and chemicals with the sediment and its inhabitants while preventing them moving in or out.

After a week of growth, they looked carefully for colonies in the gel. Many were so small they could only be seen with a microscope. But on average 22 per cent of bacteria seen in the sediment samples were able to grow in the simulated tidal environment鈥攁bout 300 times more than grew on standard Petri dishes.

In theory, the technique could be tweaked to grow any bug by simulating its natural environment. The biologists have already identified a pair of formerly unknown microbes, and are now studying several more.

The researchers also found that, once purified, some of these 鈥渆lusive鈥� microbes can grow on conventional Petri dishes, but only when another bacterial strain is present. 鈥淭hat suggests they are sophisticated,鈥� says Epstein. 鈥淏efore they decide to grow, they get an idea of who their neighbours are.鈥�

Stephen Giovannoni at Oregon State University in Corvallis says the new technique is an innovative way of harnessing an untapped reservoir of genetic information, as studying live bugs in the lab is the best way to understand a bacterium鈥檚 potential. His own team is working on an automated approach that quickly samples a large number of conditions to find the right growth environment for different marine bacteria.