Washington, Feb 3 (IANS): Microbes inhabit a tightly clustered world comprising co-operators, which share resources, and cheaters, those that selfishly take yet give nothing back. Surprisingly, the exploiter (cheater) and the exploited (co-operator) can co-exist, provided there is room to expand and grow, aver researchers.

According to researchers from Princeton (US) and Ben-Gurion (Israel) universities, our world and our bodies play host to a vast array of microbes.

On our teeth alone, there are approximately a thousand different kinds of bacteria, all living in very close quarters, according to a Princeton and Ben Gurion statement.

"In a fixed population, cells that share can't live together with cells that only take," said David Bruce Borenstein, researcher at Princeton.

"But if the population repeatedly expands and contracts then such 'co-operators' and 'cheaters' can co-exist."

Co-operators were given the ability to make a resource that speeds up growth in both kinds of cells.

Producing this resource slowed down the growth of co-operators, because they have to divert some energy to the process.

The researchers' computer model revealed that the producers tended to cluster, meaning that being a producer gave you greater access to resources.

It also meant that even though cheaters are avoiding the cost of production, they pay for it with reduced resource access.

Within these basic constraints it was found that when the two populations must compete directly for survival, no co-existence is possible.

"One type always wins out," observed Borenstein.

"To our astonishment, we found that while cheaters can exploit co-operators, co-operators can isolate cheaters, just from co-operation and growth," concluded Borenstein.

"As a result, the community can persist in a sort of perpetual race from which a winner need not emerge."

These findings were presented at the 57th Annual Meeting of the Biophysical Society (BPS), in Philadelphia, US.