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

Summary

Researchers discovered that bacteria living on frog skin can protect against a dangerous water mold called Saprolegnia that kills amphibian eggs and young tadpoles. They tested 196 different bacteria from frogs in Portugal and found that certain bacteria, especially Bacillus species, could stop the mold from growing. Interestingly, these bacteria worked best in clean water environments with fewer nutrients, similar to natural pond conditions, suggesting nature has built-in protections for amphibians.

Background

Amphibian populations have experienced severe decline due to environmental pollution, habitat destruction, climate change, and disease. Saprolegnia species are water molds that cause saprolegniosis, affecting amphibians particularly in early developmental stages. The study reports the first identification of saprolegniosis in Pelophylax perezi egg masses in Portugal.

Objective

To screen bacterial isolates from P. perezi skin microbiomes for antagonistic activity against Saprolegnia spp., assess whether antagonistic potential depends on sampling site environmental conditions, evaluate the influence of different culture media on bacterial antagonistic capabilities, and identify the causative pathogen of P. perezi saprolegniosis.

Results

The pathogen was identified as Saprolegnia australis. Among 196 bacterial isolates, 26 showed antagonistic activity against at least one Saprolegnia strain, predominantly from genera Bacillus, Serratia, Pseudomonas, and Aeromonas. Antagonistic activity varied significantly between nutrient-poor (R2A) and nutrient-rich (PG) media, with 14% strong inhibition in R2A dropping to 3% in PG.

Conclusion

Amphibian skin bacteria demonstrate significant protective potential against Saprolegnia spp., with activity dependent on bacterial composition, environmental origin, and culture conditions. Nutrient-limited environments favor bacterial antimicrobial compound production, suggesting natural aquatic conditions better support protective bacterial function against water mold infections in amphibians.
  • Published in:Journal of Fungi (Basel),
  • Study Type:Experimental/In vitro Study,
  • Source: PMC12471046; PMID: 41003195; DOI: 10.3390/jof11090649
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