Bacteria that thrive on Earth may…

Bacteria that thrive on Earth may not survive easily on Mars, where the soil contains toxic perchlorate salts at levels that can reach about 1 percent by weight. Researchers at the Indian Institute of Science have now shown how a brick building soil bacterium responds to this chemical and discovered that although the toxin slows growth and stresses the cells, it can also yield stronger biocemented Martian bricks.

The work builds on earlier studies in which the team used the soil bacterium Sporosarcina pasteurii to turn synthetic Martian or lunar soil into solid "space bricks." When the microbe is supplied with urea and calcium in a granular simulant along with the natural polymer guar gum, it precipitates calcium carbonate crystals that bind soil grains together, a process known as biocementation. In contrast to previous experiments that relied on a standard laboratory strain, the new study used a more robust, native strain of S. pasteurii that the researchers had isolated from soils in Bengaluru.

After confirming that the Bengaluru strain could efficiently generate mineral precipitates in the simulant, the team introduced perchlorate at concentrations similar to those detected in Martian regolith. In collaboration with scientists at the Indian Institute of Science Education and Research in Kolkata, they observed that the chemical stressed the bacteria: cells divided more slowly, shifted from rod like to more circular shapes, and began to clump into multicellular like aggregates. Stressed cells also secreted greater amounts of extracellular matrix, a mixture of proteins and other molecules that formed a coating around the microbe clusters.