Amoebae pack their lunch before travel

Houston: Do you know what's common between amoebae and humans? Well, some amoebae do what many of us do -- packing a lunch before travel.

Researchers at Rice University in Houston found that the social amoebae Dictyostellum discoideum, commonly known as slime molds, increase their odds of survival with the help of a rudimentary form of agriculture.

Some of them, the "farmer" class, sequester their food -- particular strains of bacteria -- for later use, the way we preserve our food for future, the scientists said, adding that the findings would help understand why tuberculosis bacteria invade cells and escape treatment.

"We now know that primitively social slime molds have genetic variation in their ability to farm beneficial bacteria as a food source," said George Gilchrist of National Science Foundation's Division of Environmental Biology, which funded the research.

"But the catch is that with the benefits of a portable food source, comes the cost of harbouring harmful bacteria."

After these 'farmer' amoebae aggregate into a slug, they migrate in search of nourishment and form a fruiting body, or a stalk of dead amoebae topped by a sorus, a structure containing fertile spores.

Then they release the bacteria-containing spores to the environment as feedstock for continued growth, the authors reported in the journal Nature.

The findings run counter to the presumption that all 'Dicty' eat everything in sight before they enter the social spore-forming stage.

Non-farmer amoebae do eat everything, but farmers were found to leave food uneaten, and their slugs don't travel as far, the researchers said.

Debra Brock, who led the research, said that carrying bacteria is a genetic trait by eliminating all living bacteria from four farmers and four non-farmers (the control group) by treating them with antibiotics.

It was found that all amoebae were grown on dead bacteria -- confirming that they were free of live bacteria.

When the eight clones were then fed live bacteria, the farmers all regained their abilities to seed bacteria colonies, while the non-farmers did not.

The findings, the researchers said, has implications for treating disease as it may, for instance, provide clues to the way tuberculosis bacteria invade cells, infecting the host while resisting attempts to break them down.

The results, they added, also demonstrate the importance of working in natural environments with wild organisms whose complex ties to their living environment have not been broken.