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Shifts in bacterial communities of eggshells and antimicrobial activities in eggs during incubation in a ground-nesting passerine.

Grizard S, Versteegh MA, Ndithia HK, Salles JF, Tieleman BI - PLoS ONE (2015)

Bottom Line: Regarding the antimicrobials, we notice a decrease of pH and lysozyme concentration, while ovotransferrin concentration increases during incubation.Lastly, our results provide limited evidence of significant correlation between antimicrobial compounds and bacterial communities.Identifying invading microbes and their roles in embryo mortality, as well as understanding the role of the eggshell microbiome, might be key to better understand avian strategies of immune maternal investment.

View Article: PubMed Central - PubMed

Affiliation: Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands; Department of Microbial Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands.

ABSTRACT
Microbial invasion of egg contents is a cause of embryonic death. To counter infection risks, the embryo is protected physically by the eggshell and chemically by antimicrobial proteins. If microbial pressure drives embryo mortality, then females may have evolved, through natural selection, to adapt their immune investment into eggs. Although frequently hypothesized, this match between immune allocation and microorganisms has not been explored yet. To examine if correlations between microbes on eggs and immunity in eggs exist, we collected eggs from red-capped larks (Calandrella cinerea) and simultaneously examined their bacterial communities and antimicrobial components--pH, lysozyme and ovotransferrin--during natural incubation. Using molecular techniques, we find that bacterial communities are highly dynamic: bacterial abundance increases from the onset to late incubation, Shannon's α-diversity index increases during early incubation stages, and β-diversity analysis shows that communities from 1 day-old clutches are phylogenetically more similar to each other than the older ones. Regarding the antimicrobials, we notice a decrease of pH and lysozyme concentration, while ovotransferrin concentration increases during incubation. Interestingly, we show that two eggs of the same clutch share equivalent immune protection, independent of clutch age. Lastly, our results provide limited evidence of significant correlation between antimicrobial compounds and bacterial communities. Our study examined simultaneously, for the first time in a wild bird, the dynamics of bacterial communities present on eggshells and of albumen-associated antimicrobial components during incubation and investigated their relationship. However, the link between microorganisms and immunity of eggs remains to be elucidated further. Identifying invading microbes and their roles in embryo mortality, as well as understanding the role of the eggshell microbiome, might be key to better understand avian strategies of immune maternal investment.

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Related in: MedlinePlus

Repeatability of albumen antimicrobials among and within clutches.Clutch ID is given by a letter and followed by its age (LetterNumber), and is consistent across plots. Clutch age corresponds to the number of days that the complete clutch spent in the nest; day 1 is the day of clutch completion. Only complete nests (i.e containing two eggs) are plotted and ordered by clutch age. Within each plot, one clutch is represented by the values of its two eggs (black dots) and by their mean value (±S.E.) (grey dots with error-bars). Clutches are ordered by age, the youngest starting on the left part of the graphs. (A) pH, (B) lysozyme and (C) ovotransferrin concentrations.
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pone.0121716.g003: Repeatability of albumen antimicrobials among and within clutches.Clutch ID is given by a letter and followed by its age (LetterNumber), and is consistent across plots. Clutch age corresponds to the number of days that the complete clutch spent in the nest; day 1 is the day of clutch completion. Only complete nests (i.e containing two eggs) are plotted and ordered by clutch age. Within each plot, one clutch is represented by the values of its two eggs (black dots) and by their mean value (±S.E.) (grey dots with error-bars). Clutches are ordered by age, the youngest starting on the left part of the graphs. (A) pH, (B) lysozyme and (C) ovotransferrin concentrations.

Mentions: pH did not differ between two eggs of the same clutch (χ2 = 1.71, P = 0.19), independent of clutch age, and repeatability was 0.31 (±0.22) (Fig 3A). As for lysozyme, two eggs from the same nest had significantly more similar concentrations compared to two eggs of two random nests (χ2 = 9.72, P = 0.002), independent of clutch age. Lysozyme repeatability was 0.67 (±0.14) (Fig 3B), indicating that the variation among clutches (CVa = 0.33) was relatively higher than the variation within clutches (CVw = 0.13). Ovotransferrin concentrations were not different among nests (χ2 = 0.05, P = 0.82), independent of clutch age. This was confirmed by a low repeatability of 0.05 (±0.25) (Fig 3C), indicating that the variation among clutches (CVa = 0.25) was similar to the variation within clutches (CVw = 0.24). Lysozyme and ovotransferrin concentrations did not correlate with each other (F1,12 = 0.64, P = 0.44).


Shifts in bacterial communities of eggshells and antimicrobial activities in eggs during incubation in a ground-nesting passerine.

Grizard S, Versteegh MA, Ndithia HK, Salles JF, Tieleman BI - PLoS ONE (2015)

Repeatability of albumen antimicrobials among and within clutches.Clutch ID is given by a letter and followed by its age (LetterNumber), and is consistent across plots. Clutch age corresponds to the number of days that the complete clutch spent in the nest; day 1 is the day of clutch completion. Only complete nests (i.e containing two eggs) are plotted and ordered by clutch age. Within each plot, one clutch is represented by the values of its two eggs (black dots) and by their mean value (±S.E.) (grey dots with error-bars). Clutches are ordered by age, the youngest starting on the left part of the graphs. (A) pH, (B) lysozyme and (C) ovotransferrin concentrations.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400097&req=5

pone.0121716.g003: Repeatability of albumen antimicrobials among and within clutches.Clutch ID is given by a letter and followed by its age (LetterNumber), and is consistent across plots. Clutch age corresponds to the number of days that the complete clutch spent in the nest; day 1 is the day of clutch completion. Only complete nests (i.e containing two eggs) are plotted and ordered by clutch age. Within each plot, one clutch is represented by the values of its two eggs (black dots) and by their mean value (±S.E.) (grey dots with error-bars). Clutches are ordered by age, the youngest starting on the left part of the graphs. (A) pH, (B) lysozyme and (C) ovotransferrin concentrations.
Mentions: pH did not differ between two eggs of the same clutch (χ2 = 1.71, P = 0.19), independent of clutch age, and repeatability was 0.31 (±0.22) (Fig 3A). As for lysozyme, two eggs from the same nest had significantly more similar concentrations compared to two eggs of two random nests (χ2 = 9.72, P = 0.002), independent of clutch age. Lysozyme repeatability was 0.67 (±0.14) (Fig 3B), indicating that the variation among clutches (CVa = 0.33) was relatively higher than the variation within clutches (CVw = 0.13). Ovotransferrin concentrations were not different among nests (χ2 = 0.05, P = 0.82), independent of clutch age. This was confirmed by a low repeatability of 0.05 (±0.25) (Fig 3C), indicating that the variation among clutches (CVa = 0.25) was similar to the variation within clutches (CVw = 0.24). Lysozyme and ovotransferrin concentrations did not correlate with each other (F1,12 = 0.64, P = 0.44).

Bottom Line: Regarding the antimicrobials, we notice a decrease of pH and lysozyme concentration, while ovotransferrin concentration increases during incubation.Lastly, our results provide limited evidence of significant correlation between antimicrobial compounds and bacterial communities.Identifying invading microbes and their roles in embryo mortality, as well as understanding the role of the eggshell microbiome, might be key to better understand avian strategies of immune maternal investment.

View Article: PubMed Central - PubMed

Affiliation: Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands; Department of Microbial Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands.

ABSTRACT
Microbial invasion of egg contents is a cause of embryonic death. To counter infection risks, the embryo is protected physically by the eggshell and chemically by antimicrobial proteins. If microbial pressure drives embryo mortality, then females may have evolved, through natural selection, to adapt their immune investment into eggs. Although frequently hypothesized, this match between immune allocation and microorganisms has not been explored yet. To examine if correlations between microbes on eggs and immunity in eggs exist, we collected eggs from red-capped larks (Calandrella cinerea) and simultaneously examined their bacterial communities and antimicrobial components--pH, lysozyme and ovotransferrin--during natural incubation. Using molecular techniques, we find that bacterial communities are highly dynamic: bacterial abundance increases from the onset to late incubation, Shannon's α-diversity index increases during early incubation stages, and β-diversity analysis shows that communities from 1 day-old clutches are phylogenetically more similar to each other than the older ones. Regarding the antimicrobials, we notice a decrease of pH and lysozyme concentration, while ovotransferrin concentration increases during incubation. Interestingly, we show that two eggs of the same clutch share equivalent immune protection, independent of clutch age. Lastly, our results provide limited evidence of significant correlation between antimicrobial compounds and bacterial communities. Our study examined simultaneously, for the first time in a wild bird, the dynamics of bacterial communities present on eggshells and of albumen-associated antimicrobial components during incubation and investigated their relationship. However, the link between microorganisms and immunity of eggs remains to be elucidated further. Identifying invading microbes and their roles in embryo mortality, as well as understanding the role of the eggshell microbiome, might be key to better understand avian strategies of immune maternal investment.

Show MeSH
Related in: MedlinePlus