Biofilm-producing bacteria could stabilize buildings.

Bacteria that secrete a sticky goo can increase the strength of soil, a trait that scientists say could eventually prevent damage to buildings in sandy, earthquake-prone areas.

When an earthquake strikes, it can shake soil so violently that it breaks up, sometimes leading to the collapse of buildings. Currently, the most common way to stabilize earthquake-vulnerable buildings is to flow cement into the soil beneath them. However, because the cement can set up unevenly, it tends to provide only patchy support for a building.

Seeking a better way to strengthen soil, Laurie Caslake and Mary Roth of Lafayette College in Easton, Pa., looked to Flavobacterium johnsoniae, a bacterial species that secretes a viscous, sticky polymer that forms what's called a biofilm.

To see whether they could turn the polymers of such biofilms to their advantage, Caslake and Roth mixed sand with a liquid culture of F.johnsoniae in a suitcase-size box. After giving the bacteria several days to colonize the sand, the researchers measured the sand's cohesion with an instrument that assesses particles' tendency to slide past each other. The team found that sand colonized by the bacteria was almost twice as solid as sand without the biofilm-producing microbes.

Although the researchers stress that more testing is necessary to confirm that the bacteria actually strengthen soil and will spread evenly through it, they suggest that biofilms may eventually provide a viable alternative to cement for fortifying soils in earthquake zones.--C. B.