“Molecular diversity of aquatic Pseudomonas spp. with inhibitory activity against Saprolegnia water mould (Oomycota) (7121)”

Molecular diversity of aquatic Pseudomonas spp. with inhibitory activity against Saprolegnia water mould (Oomycota)

Introduction: The fungal-like oomycete water moulds can occur in freshwater ecosystems and pose a significant threat to both freshwater environments and fish farms worldwide. The fish pathogen water moulds belong to the genera Saprolegnia, Achlya, and Phytium, and they cause a disease called saprolegniosis. Control options are limited, leading to growing interest in bio-based solutions. Among others, bacterial species of the genus Pseudomonas can inhibit the growth of water moulds. In the present study, we isolated Pseudomonas strains from aquatic environment, analysed their genetic diversity and protein profiles, and tested their inhibitory effects against various Saprolegnia species in vitro.

Methodology: Pseudomonas bacterial strains were isolated from water, fish eggs, and fry originating from fish farms and natural waters in Hungary. Species identification was based on 16S rRNA and rpoD gene sequencing, and phylogenetic relationships were examined using the maximum-likelihood method. Protein fingerprinting was carried out using MALDI-TOF MS. The inhibitory effect against Saprolegnia parasitica, S. ferax, S. australis, and S. velencensis was measured on agar plates and in liquid media.

Results: All 24 tested Pseudomonas strains showed inhibitory effects against the Saprolegnia species. All bacteria belonged to the P. fluorescens taxonomic group. Our study was the first to demonstrate that P. danubii, P. canadensis, P. shahriarae, P. salmasensis, and P. chlororaphis have anti-water mould activity. Several strains of P. danubii and the Pseudomonas sp. strain B379-HU showed outstanding inhibitory effects. The bacteria deformed the hyphal tips through branching and nodule formation, and in cases of complete inhibition, the hyphae were fragmented or completely destroyed.

Conclusion: The study confirmed that several Pseudomonas species are effective in inhibiting the growth of water moulds and could be potential candidates for biological control. Our future research will focus on identifying the active inhibitory compounds produced by these bacteria and, in the long term, on developing a method for their practical application in aquaculture.

This research was supported by the National Research, Development and Innovation Office under grant number K141889.

1. Vámosi, Réka, HUN-REN Veterinary Medical Research Institute, Presenter
2. Erdei, Noémi, HUN-REN Veterinary Medical Research Institute, Author
3. Kóczán, Patrícia, HUN-REN Veterinary Medical Research Institute, Author
4. Farkas, Milán, Hungarian University of Agriculture and Life Sciences, Author
5. Kaján, Győző, HUN-REN Veterinary Medical Research Institute, Author
6. Sipos, Dóra, HUN-REN Veterinary Medical Research Institute, Author
7. Sváb, Domonkos, HUN-REN Veterinary Medical Research Institute, Author
8. Kaszab, Edit, Hungarian University of Agriculture and Life Sciences, Author
9. Eszterbauer, Edit, HUN-REN Veterinary Medical Research Institute, Author