Bacteria used to create "living" building materials

We've already heard about experimental self-healing concrete, that can repair cracks within itself. Now, scientists have gone a step further, utilizing bacteria to create building materials that can be grown on-site – and that regenerate when broken.

Led by Asst. Prof. Wil Srubar, a team from the University of Colorado at Boulder started by combining sand and a gelatine-based hydrogel. This mixture was then placed in brick-shaped molds, to which Synechococcus cyanobacteria were added. The internal structure of the mix served as scaffolding in which the microbes could essentially "roost."

The bacteria proceeded to grow as they absorbed carbon dioxide gas from the surrounding environment, producing calcium carbonate in the process. The latter mineralized the hydrogel into a sort of mortar, thus binding the sand particles together to form solid bricks.

In tests conducted so far, it was found that about 9 to 14 percent of the bacterial colonies were still alive 30 days after the bricks were formed – even that success rate is only possible if the bricks are kept in an environment with a Synechococcus-friendly level of humidity. This presents a challenge, as the bricks are at their strongest when they're completely dried out. With that in mind, the scientists are now working on developing microbes that could survive under much more arid conditions.

Ultimately, it is hoped that the technology could find use in building materials that can be grown on location from supplied ingredients, and that have self-healing capabilities.

In fact, it's already been shown that if half of an "established" brick is placed in a mold with more of the gel and sand, the bacteria from that half will migrate out and colonize the new material, eventually forming another brick. Ultimately, one parent brick – that's initially broken in two – can be used to produce up to eight other bricks.

As an added bonus, building materials made with the bacteria would actually help sequester excess carbon dioxide gas from the environment. The opposite is true of conventional concrete, as production of the cement used within it is one of the major sources of manmade CO2 emissions.

"We already use biological materials in our buildings, like wood, but those materials are no longer alive," says Srubar. "We're asking: Why can't we keep them alive and have that biology do something beneficial, too?".

The research is described in a paper that was published this week in the journal Matter.

Sources: University of Colorado at Boulder, Cell Press via EurekAlert