Microbial infection risk predicts antimicrobial potential of avian symbionts Martínez-Renau, Ester Martín-Vivaldi Martínez, Manuel Lorenzo Martín Platero, Antonio Manuel Antimicrobial activity Antibiotic-producing bacteria Birds Natural selection Symbiotic bacteria Uropygial gland Uropygial secretion Funding EM-R was financed by a predoctoral contract (PRE2018-085378) while the whole research group received funds from the projects CGL2017-83103-P, PID2020-117429GB-C21, and PID2020-117429GB-C22, funded by the Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación/10.13039/501100011033 and by “Fondo Europeo de Desarrollo Regional, a way of making Europe.” The research group also benefits from facilities, including accommodation, provided by the City Hall of Guadix, where a small lab to quickly process the samples was installed. Data availability statement Data used in this paper can be found in CSIC Institutional Repository: https://doi.org/10.20350/digitalCSIC/14748. Symbiotic bacteria on animal hosts can prevent pathogenic bacterial infections by several mechanisms. Among them, symbiotic bacteria can indirectly enhance host’s immune responses or, directly, produce antimicrobial substances against pathogens. Due to differences in life-style, different host species are under different risks of microbial infections. Consequently, if symbiotic bacteria are somewhat selected by genetically determined host characteristics, we would expect the antimicrobial properties of bacterial symbionts to vary among host species and to be distributed according to risk of infection. Here we have tested this hypothesis by measuring the antimicrobial ability of the bacterial strains isolated from the uropygial-gland skin of 19 bird species differing in nesting habits, and, therefore, in risk of microbial infection. In accordance with our predictions, intensity and range of antimicrobial effects against the indicator strains assayed varied among bird species, with hole-and open-nesters showing the highest and the lowest values, respectively. Since it is broadly accepted that hole-nesters have higher risks of microbial infection than open nesters, our results suggest that the risk of infection is a strong driver of natural selection to enhance immunocompetence of animals through selecting for antibiotic-producing symbionts. Future research should focus on characterizing symbiotic bacterial communities and detecting coevolutionary processes with particular antibiotic-producing bacteria within-host species. 2022-12-21T12:42:13Z 2022-12-21T12:42:13Z 2022-11-21 journal article Martínez-Renau E, Mazorra-Alonso M, Ruiz-Castellano C, Martín-Vivaldi M, Martín-Platero AM, Barón MD and Soler JJ (2022) Microbial infection risk predicts antimicrobial potential of avian symbionts. Front. Microbiol. 13:1010961. [doi: 10.3389/fmicb.2022.1010961] https://hdl.handle.net/10481/78586 10.3389/fmicb.2022.1010961 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional Frontiers Media