The aim of the present study was to investigate the microbial community of skin mucus of infected and uninfected Prussian carp caused by parasitic crustaceans from the genus Argulus and Lernaea in an eutrophic lake with parallel studying of associated microbiota of their parasites and environmental compartments. In this study the libraries containing 16S ribosomal RNA genes from these distinct biological sources were studied using next-generation high-throughput sequencing and bioinfomratic software for identification and classification of operational taxonomic units (OTUs). In the microbial community associated with the parasitic crustaceans Argulus sp. and Lernaea sp., along with representatives of the normal microbiota, there were identified microorganisms that could be potential agents of infectious diseases in fish (Flavobacterium sp., Aeromonadaceae sp., Corynebacterium sp. and Streptococcus sp.). Each parasite is characterized by a specific structure of its associated microbiota, which, apparently, may indicate their role as vectors of different infectious disease.
Significant perturbation of dominant microbiota of skin mucus of unhealthy fish in comparison with healthy fish was registered (ADONIS, p≤0.05). Microbiota of intact skin mucosa of unhealthy fish were dominated by Corynebacterium (10.03±1.82%), Arcobacter (5.47±0.97%), and unclassified genus from Comamonadaceae family (4.44±0.48%). The microbiota of intact skin mucosa of healthy fish was opposite dominated by Arcobacter (12.57±3.49%), unclassified genus from Comamonadaceae (6.40±1.13%) and Helicobacteraceae families (4.37±1.47%). According to the Spearman rank correlation test the increase of ulceration load in skin of Prussian carp were significantly correlated with reduce the abundance of Acrobacter, bacteria C39 from Rhodocyclaceae family, Rheinheimera, unclassified bacteria from Helicobacteraceae, Aeromonadaceae family, and Vogesella (p≤0.05). Relative abundance of known opportunistic pathogens (Flavobacterium and Acrobacter) found in intact skin and ulcers of infected Prussian carp were significantly correlated with the ability of Argulus sp. and Lernaea sp. The microbiota associated with Lernaea sp. was significantly different from microbial communities of intact skin mucosa of both infected and uninfected fish and skin ulcers (ADONIS, p≤0.05) and represented by unclassified bacteria from Comamonadaceae and Aeromonadaceae families (33.93± and 8.44±5.97%, respectively). Associated microbiota of Argulus sp. was dominated by Flavobacterium (17.95±16.19%) and Corynebacterium (10.61±5.0%). Results of conducted studies indicate that ectoparasites have the potential to alter skin microbiota and play possible role in transmission of secondary bacterial infection in fish.