Passage IV

Talking Bacteria

In her lab at Princeton University, molecular biologist, Bonnie Bassler leans over a collection of petri dishes; her face illuminated by an aquamarine glow. The glow, caused by a particular species, of bacteria is confirmation of a phenomenon Bassler has been investigating for years. Bacteria, the simplest forms of life, have the ability to communicate with each other.

As a student in graduate school, Bassler became intrigued with other researchers’ and their discoveries involving Vibrio fischeri; a luminescent marine bacteria. Researchers found that these bacteria only begin to glow once they have formed a group. A series of experiments revealed that each bacterial cell releases an autoinducer, a type of chemical signal. A sensory protein allowed other bacteria to “hear” this molecular message. Once the bacteria have released a high enough concentration of autoinducer, they assemble and begin to glow. This “quorum sensing” enables the bacteria to coordinate their actions and perform their specific function.

On the contrary, in her own lab, Bassler found evidence of quorum sensing in a related bacterial species called Vibrio harveyi. She also discovered that V. harveyi release a second autoinducer, or AI-2. This AI-2, which Bassler has described as a chemical “trade language,” makes it possible for bacteria to communicate with other species of bacteria in the same neck of the woods. She found that each of the species she studied, including ones that live in humans, releases AI-2.

After her 2002 discovery, Bassler began using information from her quorum-sensing studies to understand how virulent strains of bacteria found in humans communicate. These disease-spreading bacteria rely on quorum sensing to spread disease. Bassler is hopeful that her ongoing studies of AI-2 will enable she and her team to disrupt quorum sensing.(59)