Bacteriocins with a broader antimicrobial spectrum prevail in enterococcal symbionts isolated from the hoopoe's uropygial gland

Abstract

The use of compounds produced by symbiotic bacteria against pathogens in animals is one of the most exciting discoveries in ecological immunology. The study of those antibiotic metabolites will enable an understanding of the defensive strategies against pathogenic infections. Here, we explore the role of bacteriocins explaining the antimicrobial properties of symbiotic bacteria isolated from the uropygial gland of the hoopoe (Upupa epops). The antagonistic activity of 187 strains was assayed against eight indicator bacteria, and the presence of six bacteriocin genes was detected in the genomic DNA. The presence of bacteriocin genes correlated with the antimicrobial activity of isolates. The most frequently detected bacteriocin genes were those encoding for the MR10 and AS-48 enterocins, which confer the highest inhibition capacity. All the isolates belonged to the genus Enterococcus, with E. faecalis as the most abundant species, with the broadest antimicrobial spectrum and the highest antagonistic activity. The vast majority of E. faecalis strains carried the genes of MR10 and AS-48 in their genome. Therefore, we suggest that fitness-related benefits for hoopoes associated with harbouring the most bactericidal symbionts cause the highest frequency of strains carrying MR10 and AS-48 genes. The study of mechanisms associated with the acquisition and selection of bacterial symbionts by hoopoes is necessary, however, to reach further conclusions.

Environmental Factors Shape the Community of Symbionts in the Hoopoe Uropygial Gland More than Genetic Factors

“…In accordance with a possible process of symbiont selection and the effect of environments determining their bacterial community, we found that E. faecalis, the species with the greatest antibiotic activity (35), is the culturable bacterium that is prevalent in hoopoe glands (36). Thus, it is possible that the community of symbionts in the UG of hoopoes is a plastic trait conditioned by particularities of the nest environment each year.…”

“…Although we cannot rule out the possible presence of bacteria that cannot be cultured, our results imply a certain specialization in hosting enterococci. Earlier studies have shown the relationship of bacteriocin production to the antimicrobial capacity of isolated colonies and also the association between genotypes and antimicrobial properties (15,35,36). Moreover, we know that hoopoes derive fitness advantages from harboring these symbionts (14,21), suggesting a mutualistic relationship between enterococci and hoopoes.…”

“…On the other hand, nestlings may acquire symbionts vertically from mothers and/or horizontally from nest remains of previous reproduction events of con-or heterospecifics. Previous studies have shown that the dominant group of cultivable bacteria in the UGS of hoopoes belongs to the genus Enterococcus (14,35,36) and that some isolated strains from hoopoes produce compounds with strong antagonistic activity against other bacterial species (15,16). Enterococci are common bacteria that can be found in soil and plants (37,38) or in the gastrointestinal tract of birds (39,40) and could therefore be easily acquired from different sources.…”

“…Enterococci are common bacteria that can be found in soil and plants (37,38) or in the gastrointestinal tract of birds (39,40) and could therefore be easily acquired from different sources. Moreover, it is known that the antimicrobial properties of different Enterococcus bacterial strains harbored by hoopoes differ and that those with broader antimicrobial spectra are the most common in the UGS of hoopoes (35,36). The mechanisms responsible for acquisition of symbionts with the highest potential benefits are unknown, and thus it is an ideal system for exploring the importance of vertical transmission relative to that of horizontal transmission in explaining the symbiotic microbiota.…”

The Antibacterial Effects of Antimicrobial Peptides OP-145 against Clinically Isolated Multi-Resistant Strains

“…Antimicrobial peptides (AMPs) are one of the types of antimicrobial agents used to treat infection diseases (6). Natural antibacterial peptides have a wide antimicrobial spectrum (7), particularly with the ability to eradicate multidrug-resistant bacteria (8), and antibacterial peptides exhibit good thermal stability and solubility in water. One of the best-studied AMP is human LL-37, which is the only cathelicidin peptide found in humans.…”