Bacteria Develops App-like Genes to Thrive in Toxic Soil

Good news for polluted soil! Researchers at Washington State University (WSU) have identified a set of genes that allow certain soil bacteria to not only survive but thrive in environments with high levels of toxic nickel. This discovery, published in the journal Proceedings of the National Academies of Sciences, could be a game-changer for bioremediation efforts aimed at restoring polluted lands.

The study focused on a type of soil bacteria called rhizobia, which plays a crucial role in legume plant health. These beneficial bacteria form symbiotic relationships with legumes like soybeans and alfalfa, helping them fix nitrogen from the air, essentially acting as a natural fertilizer.

The research team, led by Dr. Stephanie Porter, a WSU evolutionary ecologist, collected samples of wild rhizobia bacteria from grasslands across Oregon and California. They compared bacteria from areas with naturally high nickel concentrations (serpentine soils) to those from areas with lower nickel levels.

Through genetic analysis, the researchers pinpointed a specific set of genes, called the nickel resistance operon, that allows these bacteria to tolerate and pump out nickel, preventing it from reaching toxic levels within the cell. Interestingly, they also found that the effectiveness of these genes varied depending on the nickel content of the soil. Bacteria from high-nickel environments had more potent versions of these resistance genes, allowing them to withstand greater levels of the metal.

"It's like a perfect match between the bacteria and their environment," explained Dr. Porter. "This highlights the remarkable process of evolution, where organisms develop adaptations that precisely fit the challenges of their habitat."

The researchers are now delving deeper into how this adaptation occurs. Unlike animals, bacteria can share genetic information not just through reproduction but also through a process called horizontal gene transfer. This fascinating mechanism allows bacteria to "download" sets of genes from other bacteria they come in contact with, similar to downloading an app on a smartphone.

"Imagine two bacteria bumping into each other in the soil," said co-author Angeliqua Montoya, a Ph.D. candidate in Dr. Porter's lab. "One bacterium might share a 'mobile' set of genes containing the nickel resistance operon. The recipient bacterium then incorporates this new DNA into its own genome, gaining the ability to thrive in high-nickel environments."

This process, while beneficial in some cases like the nickel-resistant rhizobia, can also be problematic. Many harmful bacteria, such as antibiotic-resistant strains, acquire resistance through horizontal gene transfer.

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