Coaxing purple bacteria into becoming bioplastic factories

In a world overrun by petroleum-based plastics, scientists are searching for alternatives that are more sustainable, more biodegradable and far less toxic to the environment.

Two new studies by biologists at Washington University in St. Louis highlight one potential source of game-changing materials: purple bacteria that, with a little encouragement, can act like microscopic factories for bioplastics.

A study led by graduate student Eric Conners found that two relatively obscure species of purple bacteria have the ability to produce polyhydroxyalkanoates (PHAs), natural polymers that can be purified to make plastic.

Another study led by research lab supervisor Tahina Ranaivoarisoa showed that genetic engineering could coax a well-studied but notoriously stubborn species of purple bacteria to dramatically ramp up its production of PHAs.

The bacteria naturally produce PHAs and other building blocks of bioplastics to store extra carbon. Under the right conditions, they can keep producing those polymers indefinitely.

As the WashU biologists report this week in Microbial Biotechnology, two little-known species of purple bacteria in the genus Rhodomicrobium showed a remarkable willingness to produce polymers, especially when energized with small amounts of electricity and nourished with nitrogen.

Image source: Joe Angeles/WashU.