Despite many studies showing that amphibians synthesize and secrete a remarkably diverse array of antimicrobial substances in their skin, little is known about the molecules produced in their brains. Rui Liu and colleagues decided to begin filling that knowledge gap by analyzing brains from the Giant Fire-Bellied Toad (Bombina maxima), and the Small-webbed Bell Toad (Bombina microdeladigitora). They discovered 79 different antimicrobial peptides, the components of proteins, including 59 that were totally new to science. The diversity of the peptides "is, to our knowledge, the most extreme yet described for any animal brains," they noted. Some of the peptides showed strong antimicrobial activity, crippling or killing strains of staph bacteria, E. coli, and the fungus that causes yeast infections in humans. These promising findings suggest that the toad brains might be a valuable source for developing new antibacterial and antiviral drugs. The antimicrobial peptides discovered belong to two peptide groups (maximin and maximin-H). Some of the antimicrobial peptides showed strong antimicrobial activities against Gram-positive and -negative bacteria and fungi.
Rui Liu, Huan Liu, Yufang Ma, Jing Wu, Hailong Yang, Huahu Ye, Ren Lai. There are Abundant Antimicrobial Peptides in Brains of Two Kinds of Bombina Toads. Journal of Proteome Research, 2011; 10 (4): 1806 DOI: 10.1021/pr101285n