Spheniscins, Avian β-Defensins in Preserved Stomach Contents of the King Penguin, Aptenodytes patagonicus

Abstract

During the last part of egg incubation in king penguins, the male can preserve undigested food in the stomach for several weeks. This ensures survival of the newly hatched chick, in cases where the return of the foraging female from the sea is delayed. In accordance with the characterization of stress-induced bacteria, we demonstrate the occurrence of strong antimicrobial activities in preserved stomach contents. We isolated and fully characterized two isoforms of a novel 38-residue antimicrobial peptide (AMP), spheniscin, belonging to the ␤-defensin subfamily. Spheniscin concentration was found to strongly increase during the period of food storage. Using a synthetic version of one of two spheniscin isoforms, we established that this peptide has a broad activity spectrum, affecting the growth of both pathogenic bacteria and fungi. Altogether, our data suggest that spheniscins and other, not yet identified, antimicrobial substances may play a role in the long term preservation of stored food in the stomach of king penguins.Lack of food resources induced by climatic changes may impair the breeding success of wild animals. For king penguins, the female usually comes back from foraging at sea to feed the chick at hatching. However, in relation to the circumpolar wave, thought to be linked with the El Niñ o Southern Oscillation phenomenon (1), the return of the female may be delayed due to the necessity of foraging at a greater distance than usual. The survival of the chick can still be ensured by the male, as it can provide food preserved in its stomach during the final 3 weeks of incubation (2, 3). A remaining unanswered question is how can food be preserved from attack by microorganisms, when the rich 38°C buffered growth medium (3, 4) and a long retention time in the stomach would be expected to favor microbial colonization (5, 6). The maintained mass and energetic value of the food throughout the fast (3) and the stressed-induced characteristics of the stomach bacteria (4) altogether suggest the existence of a protection mechanism against food degradation by microorganisms.Like other mucosal surfaces, the gastrointestinal tract surface interacts directly with the external environment and therefore has to be protected from damage and invasion by ingested or indigenous microorganisms. One established facet of epithelial host defense is the synthesis and secretion of AMPs 1 (7,8). The role of these AMPs is not limited to epithelial protection through innate immune responses since they can attract human blood cells, alert the adaptive immune system and induce gastrointestinal secretions (8 -10). It has also been assumed that some AMPs influence the resident microflora in the small intestine lumen (11,12). An additional role could then be the participation of AMPs in the control of microbial proliferation, contributing to the preservation of retained food.In the present study, we found numerous, strongly active antimicrobial substances in the stomach contents of male penguins that efficiently conserve food during th...

Preparation and Characterization of Nanoparticles Shelled with Chitosan for Oral Insulin Delivery

“…30 The fasting pH of the stomach is about 2.5-3.7. 31,32 In the presence of food, the stomach pH is about 1.0-2.0, due to hydrochloric acid secreted by parietal cells. 33 The proximal part of the small intestine (duodenum) has a pH of about 6.0-6.6 due to neutralization of the acid by bicarbonates secreted by the duodenal mucosa and pancreas.…”

Purification and Characterization of Avian β-Defensin 11, an Antimicrobial Peptide of the Hen Egg

“…The tertiary structure of AvBD103b is very similar to those of mammalian ␤-defensins, including the common array of disulfide bonds and the presence of a three-stranded ␤-sheet as the main secondary structure element (15,26). AvBD103b was isolated from the stomach contents of the king penguin and exhibits a wide spectrum of antimicrobial activity against Gram-positive and Gram-negative bacteria, yeasts, and fungi (29). The high potency of AvBD103b against bacteria was correlated with its extreme cationicity but also with the presence of a hydrophobic patch which is not present in mammalian ␤-defensins (15).…”

Three-dimensional NMR Structure of Hen Egg Gallin (Chicken Ovodefensin) Reveals a New Variation of the β-Defensin Fold

“…The observed anti-E. coli effect is in agreement with previous results showing that gallin at a concentration of 0.25 M was able to inhibit the growth of an E. coli strain different from those used in our study (34). In contrast, no activities against the other tested bacteria, including Gram-negative (S. enterica serovar Enteritidis and S. enterica serovar Typhimurium) and Gram-positive (S. aureus and L. monocytogenes) bacteria, were observed for gallin at a maximal concentration of 53 M. These results are unexpected because generally defensins possess a broad spectrum of antimicrobial activities, targeting both Gram-positive and Gram-negative bacteria (15,21,51). However, to our knowledge, no antimicrobial activity has been revealed for the other known members of the ovodefensin family to date.…”

“…Chicken AvBD2 is shorter, lacking the amino-terminal residues, and consequently cannot form an additional amino-terminal structural element. The presence (or absence) of this amino-terminal helix cannot be related to antimicrobial properties, because both king penguin AvBD103b and chicken AvBD2 demonstrate large antimicrobial spectrum (21,51). However, the amino-terminal region could be involved in other yet unknown functions.…”