Two Probiotic Candidates of the Genus Psychrobacter Modulate the Immune Response and Disease Resistance after Experimental Infection in Turbot (Scophthalmus maximus, Linnaeus 1758)

Abstract

Probiotic bacteria are a recognized alternative to classical methods of disease prophylaxis and therapy. We tested the effects of their application on the immune reaction in juvenile turbot. To prevent digestion of the probiotics, rectal administration was applied to maximise colonization, by-passing digestion in the stomach. The application of Psychrobacter nivimaris and Psychrobacter faecalis showed beneficial effects on the inflammatory response and disease resistance after infection with the common pathogen Tenacibaculum maritimum. Treatment with P. nivimaris and P. faecalis resulted in 0% and 8% mortalities post-infection, while in the treatment control, an elevated mortality of 20% was observed. In the challenge controls (no infection), no mortalities were observed during the entire experimental period. After an experimental infection, mRNA expression of selected immune markers (mhc II α, il-1β, tcr, tgf β and tnf α) were determined by RT-QPCR at 0, 1 and 5 days post-infection (dpi). At 0 dpi, gene expression was comparable between the treatments and the treatment control, suggesting that probiotics did not act via immune stimulation of the host. At 1 dpi, all genes were up-regulated in the treatment control but not in the probiotic groups, indicating that the infection in probiotic-treated fish developed at a less severe level. At 5 dpi, mRNA expression returned to baseline levels. As a conclusion, the native probiotic candidates P. nivimaris and P. faecalis improved survival, whereas, in the control, mortality increased and expression of the immune markers was up-regulated post infection. This highlights a potential application of P. nivimaris and P. faecalis in disease prophylaxis, but further research is needed.

Influence of host phylogeny and water physicochemistry on microbial assemblages of the fish skin microbiome

“…includes opportunistic pathogens in both fish and humans and is the causative agent of disease in Red Sea marine fish (El-Sayed et al 2023 ). However, P. nivimaris and P. faecalis have also been documented to have probiotic qualities, reducing mortality rates in juvenile turbot ( Scophthalmus maximus ) exposed to Tenacibaculum maritimum (see Wuertz et al 2023 ). Ralstonia spp.…”

“…This may also change in response to environmental stressors and disease. For example, the genus Psychrobacter contains both opportunistic pathogens and symbionts, with thus both a protective function but also a disease-causing impact (El-Sayed et al 2023 , Wuertz et al 2023 ). It is well-established that when fish are stressed, their microbiomes are perturbed leading to an increase in the abundance of opportunistic pathogens, which may lead to the development of disease (Minniti et al 2017 ).…”

Biofilm formation and auto-aggregation abilities of novel targeted aqua-probiotics

“…At the same time, for the first time, probiotics were used to stimulate the growth of aquatic organisms back in 1986 [63]. Later, probiotics of various origins were used for this purpose, which had a significant effect on the growth of pathogens in fish [64][65][66][67][68][69]. Among the pathogens of hydrobionts, representtatives of the genus Vibrio deserve close attention, since some halophilic vibrios are the causative agents of vibriosis [70].…”

Effect of Soybean and Seaweed-based Diets on Growth Performance, Feed Utilization, and Gut Microbiota of Tilapia: A Systematic Review and Meta-analysis

“…Additionally, Psychrobacter spp, and Arthrobacter spp were noted in fish fed with soybean meal [51,55,59]. These microorganisms are known to possess probiotic properties, which could potentially enhance nutrient absorption and disease resistance [94][95][96][97]. The seaweed and soybean dietary components contain bioactive compounds such as isoflavones, saponins, and oligosaccharides in soybean [98][99][100], and polysaccharides, polyphenols, phycobiliproteins, and phlorotannins in seaweed [101][102][103].…”