Infection is an important source of mortality for avian embryos but parental behaviors and eggs themselves can provide a network of antimicrobial defenses. Mound builders (Aves: Megapodiidae) are unique among birds in that they produce heat for developing embryos not by sitting on eggs but by burying them in carefully tended mounds of soil and microbially decomposing vegetation. The low infection rate of eggs of one species in particular, the Australian brush-turkey (Alectura lathami), suggests that they possess strong defensive mechanisms. To identify some of these mechanisms, we first quantified antimicrobial albumen proteins and characterized eggshell structure, finding that albumen was not unusually antimicrobial, but that eggshell cuticle was composed of nanometer-sized calcite spheres. Experimental tests revealed that these modified eggshells were significantly more hydrophobic and better at preventing bacterial attachment and penetration into the egg contents than chicken eggs. Our results suggest that these mechanisms may contribute to the antimicrobial defense system of these eggs, and may provide inspiration for new biomimetic anti-fouling surfaces.
L.D. and M.D.S. conceived, designed and carried out experiments. D.N.J., C.E. and H.T.B. performed data collection and logistic support. All authors performed manuscript writing and revision.
The authors declare no competing financial interests.
This work was supported by Human Frontier Science Program Young Investigator's grant RGY-0083 and AFOSR FA9550-13-1-0222, both to M.D.S.
- © 2014. Published by The Company of Biologists Ltd