Can bacteria and ivy help block UV?

Researchers investigate algae and ivy as inorganic UV absorbers

Blue-green algae (cyanobacteria) and ivy could be used to replace titanium dioxide and zinc oxide in sunscreens and anti-ageing cosmetics, according to researchers at Harvard Medical School and the University of Tennessee Knoxville.

Cyanobacteria, which gain energy through sunlight via photosynthesis, make sunscreen molecules called mycosporines and mycosporine-like amino acids (MAAs) to protect their DNA from UV radiation. Now Emily Balskus and Christopher Walsh of Harvard Medical School have identified the genes and enzymes involved in the biosynthesis of these molecules.

They identified the responsible gene cluster in the Anabaena variabilis cyanobacterium and expressed it in Escherichia coli, which began making the molecules. Four enzymes were found to be responsible for synthesising the MAA molecules; each MMA has two amino acids linked to a central organic group and these amino acid linkages were found to determine the wavelength and strength of UV absorbance. While MAAs are already used in anti-ageing products, these are extracted directly from algae. Balskus says this work “could be a starting point for devising new routes to these molecules or analogues using a biocatalytic or biological engineering approach”.

In an unrelated study at the University of Tennessee Knoxville, biomedical engineer Mingjun Zhang is hoping to replace metal particles in sunscreens with an alternative made from ivy. Zhang found the secretions that give ivy its clinging power to contain unusually shaped nanoparticles. These particles not only form strong bonds with surfaces, but also absorb the ultraviolet rays in sunlight.