Cortisol-induced signatures of stress in the fish microbiome

Abstract

Stress experienced in intensive aquaculture can compromise fish growth, condition and immunity. Microbiome disruption may contribute to these adverse health effects, but little is known about how stress affects fish microbial communities. Here, we specifically examined the effects of stress-induced cortisol production on the fish microbiome. We exposed juvenile Atlantic salmon to a mild confinement stressor for two weeks. We then measured cortisol in the plasma, skin-mucus and faeces, and characterised the skin and faecal microbiome. Faecal and skin cortisol concentrations increased in fish exposed to confinement stress, and were positively correlated with plasma cortisol. Elevated faecal cortisol was associated with pronounced changes in the diversity and structure of the faecal microbiome. In particular, we identified a marked decline in probiotic Lactobacillales (Carnobacterium sp.) and an increase in pro-inflammatory and pathogenic taxa within the classes Clostridia and Gammaproteobacteria. In contrast, skin-mucus cortisol concentrations were lower and not associated with any detectable changes in the skin microbiome. Our results demonstrate that cortisol disrupts the gut microbiome, which may, in turn, contribute to the adverse effects of stress on fish health. They also highlight the value of using non-invasive faecal samples to monitor stress, including simultaneous determination of cortisol and stress-responsive bacteria.

Diet, Immunity, and Microbiota Interactions: An Integrative Analysis of the Intestine Transcriptional Response and Microbiota Modulation in Gilthead Seabream (Sparus aurata) Fed an Essential Oils-Based Functional Diet

“…In effect, the results from our transcriptional analysis revealed a positive regulation of processes related with a response to hormone stimulus. Changes in hormone secretion, such as cortisol, may interfere with the gut immune response (57) and microbiome (58), which could explain the obtained immunity activation and regulation of hormone-sensitive bacteria, such as those belonging to Rothia (14). Moreover, stress and stress-related hormones are known to affect carbohydrate, protein, and lipid metabolisms in fish (59), which in turn are also regulated in the host by the gut microbiota.…”

The role of the gut microbiome in sustainable teleost aquaculture

“…It is possible to measure fish welfare through physiological and behavioural indicators, with a current focus on identifying stress. The microbiome has been identified as another potential biomarker [64] due to its interaction with the host immune system, and its responsive nature to stressors [115,116]. Therefore, identifying imbalances in the gut microbiome, or dysbiosis, could be a useful predictor of stress-related syndromes, which could ultimately lead to mortality.…”

Impact of environmental micropollutants and diet composition on the gut microbiota of wild european eels (Anguilla anguilla)

“…Then, the alteration of the microbiota composition and / or its metabolic functions might (Claus et al, 2016). This phenomenon is called dysbiosis and its links with environmental stressors suggest that the microbiome has the potential to provide innovative biomarkers (Boutin et al, 2013;Webster et al, 2019) and the identification of dysbiosis might be informative regarding adverse outcomes. Still, processes that drive microbial community in fish are poorly understood.…”