Material uses live cyanobacteria to neutralize waterborne pollutants

We often hear of cyanobacteria as being the cause of toxic blue-green algae blooms in lakes and rivers. Soon, however, a 3D-printed material that incorporates the microbes could be used to help purify polluted water – and after the bacteria are finished, they'll kill themselves.

Developed by a team of scientists at the University of California San Diego, the material is made of a seaweed-derived natural polymer known as alginate, which is combined with live Synechococcus elongatus cyanobacteria.

The resulting hydrogel is printed in a waffle-like grid pattern with a high surface-area-to-volume ratio. This configuration boosts the survival of the bacteria by placing most of the microbes near the surface of the gel where they can more easily access life-sustaining nutrients, gases and sunlight.

Importantly, the cyanobacteria has been genetically engineered to produce an enzyme called laccase. Previous studies have shown how laccase is able to break down waterborne pollutants such as bisphenol A (BPA), antibiotics, pharmaceutical drugs and dyes. In lab tests, the new material successfully neutralized indigo carmine, which is a toxic dye commonly used in the production of denim blue jeans.

Of course, no one wants genetically engineered cyanobacteria lingering in the environment after the job is done. With that fact in mind, the microbes have additionally been engineered to produce a protein that destroys their single-cell bodies, when they're exposed to a natural chemical known as theophylline.

Image source: David Baillot / UC San Diego.