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Potential Protective Role of Amphibian Skin Bacteria Against Water Mold Saprolegnia spp

Summary

Frog populations are declining due to various diseases and environmental challenges. This research discovered that bacteria living on frog skin can protect against harmful water molds called Saprolegnia that attack amphibian eggs. Scientists found that different types of bacteria, particularly Bacillus species, can inhibit the growth of these water molds. The protective effect was strongest in nutrient-poor conditions similar to natural water environments, suggesting that the bacterial symbiosis with frogs may be an important defense mechanism.

Background

Amphibian populations are declining due to environmental pollution, habitat destruction, climate change, and disease. Saprolegnia species are water molds that cause saprolegniosis, particularly affecting amphibian eggs and early developmental stages. The skin microbiome of amphibians has been shown to play a protective role against fungal pathogens.

Objective

This study aimed to identify and characterize bacterial strains from Pelophylax perezi skin that inhibit Saprolegnia spp. growth, assess whether antagonistic potential varies by sampling site, evaluate how culture conditions influence bacterial antagonism, and identify the Saprolegnia species causing infection in amphibian egg masses in Portugal.

Results

Saprolegnia australis was identified as the causative agent of infection in P. perezi eggs, representing the first report of saprolegniosis in this species in Portugal. Twenty-six of 196 bacterial isolates showed antagonistic activity, with Bacillus, Pseudomonas, Serratia, and Aeromonas being the most effective genera. Antagonistic activity was significantly reduced in nutrient-rich PG medium compared to nutrient-poor R2A medium, with strong to moderate inhibition decreasing from 85% to 30%.

Conclusion

Amphibian skin bacteria possess protective potential against Saprolegnia spp., with activity dependent on both bacterial species composition and environmental nutrient availability. The presence of antagonistic bacteria in adult frogs may contribute to lower susceptibility to water mold infections compared to early developmental stages like eggs and tadpoles. These findings suggest that bacterial symbiosis and microbiome composition may be important factors in amphibian disease resistance.
  • Published in:Journal of Fungi,
  • Study Type:In vitro Experimental Study,
  • Source: PMID: 41003195, DOI: 10.3390/jof11090649
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