Antimicrobial activity of the Anseriform outer eggshell and cuticle

Area of Science:

• Biochemistry
• Microbiology
• Zoology

Background:

• The avian eggshell is a biomineral structure with an organic outer layer, the eggshell cuticle.
• The cuticle, composed of polysaccharides, lipids, and glycoproteins, may possess antimicrobial properties.
• Antimicrobial defense mechanisms are crucial for protecting developing embryos.

Purpose of the Study:

• To investigate the antimicrobial activity of eggshell cuticle and outer eggshell protein extracts.
• To identify antimicrobial proteins present in the eggshell cuticle and outer eggshell.
• To compare the antimicrobial potency among four Anseriform species.

Main Methods:

• Proteins were extracted from eggshell cuticles and outer eggshells of wood duck, hooded merganser, Canada goose, and mute swan using urea or HCl treatment.
• The presence of specific antimicrobial proteins (C-type lysozyme, ovotransferrin, ovocalyxin-32-like protein) was analyzed.
• Antimicrobial activity was tested against Staphylococcus aureus, Escherichia coli D31, Pseudomonas aeruginosa, and Bacillus subtilis.

Main Results:

• Antimicrobial proteins, including C-type lysozyme, ovotransferrin, and an ovocalyxin-32-like protein, were detected in all tested eggshell extracts.
• Eggshell cuticle and outer eggshell protein extracts demonstrated inhibitory effects on all tested bacterial species.
• Protein extracts from the cavity-nesting hooded merganser exhibited notably potent antimicrobial activity.

Conclusions:

• The avian eggshell cuticle and outer eggshell contain active antimicrobial proteins, indicating a role in innate immunity.
• Antimicrobial defenses may be enhanced in species facing specific environmental pressures, such as cavity nesters.
• Further research into these antimicrobial proteins could reveal novel applications in biotechnology and medicine.