Abstract
Concerns about safety, applicability and functionality associated with live probiotic cells have led to consideration of the use of non-viable microorganisms, known as paraprobiotics. The present study evaluated the effects of dietary administration of heat-inactivated cells of the probiotic strain Shewanella putrefaciens Ppd11 on the intestinal microbiota and immune gene transcription in Solea senegalensis. Results obtained were evaluated and compared to those described after feeding with viable Pdp11 cells. S. senegalensis specimens were fed with basal (control) diet or supplemented with live or heat inactivated (60 °C, 1 h) probiotics diets for 45 days. Growth improvement was observed in the group receiving live probiotics compared to the control group, but not after feeding with a probiotic heat-inactivated diet. Regarding immune gene transcription, no changes were observed for tnfα, il-6, lys-c1, c7, hsp70, and hsp90aa in the intestinal samples based on the diet. On the contrary, hsp90ab, gp96, cd4, cd8, il-1β, and c3 transcription were modulated after probiotic supplementation, though no differences between viable and heat-inactivated probiotic supplemented diets were observed. Modulation of intestinal microbiota showed remarkable differences based on the viability of the probiotics. Thus, higher diversity in fish fed with live probiotic cells, jointly with increased Mycoplasmataceae and Spirochaetaceae to the detriment of Brevinemataceae, was detected. However, microbiota of fish receiving heat-inactivated probiotic cells showed decreased Mycoplasmataceae and increased Brevinemataceae and Vibrio genus abundance. In short, the results obtained indicate that the viable state of Pdp11 probiotic cells affects growth performance and modulation of S. senegalensis intestinal microbiota. On the contrary, minor changes were detected in the intestinal immune response, being similar for fish receiving both, viable and inactivated probiotic cell supplemented diets, when compared to the control diet.
Highlights
Aquaculture is the fastest growing agro-industry sector in the world [1]
Fish fed with diet P exhibited significant increased rates (p < 0.05) in the final body weight, weight gain rate (WGR) and specific growth rate (SGR) compared to those receiving control and heat-inactivated probiotic
The effects of heat-inactivated cells of the probiotic strain Pdp11 on the intestinal microbiota and immune response were evaluated in S. senegalensis
Summary
Aquaculture is the fastest growing agro-industry sector in the world [1]. intensive aquaculture practices negatively affect the farmed fish physiology, disrupting the immune status and making fish prone to infectious diseases [2,3,4]. In order to contribute to aquaculture sustainability, practices to help fish maintain optimal gastrointestinal functionality are essential [5]. Fish gut mucosa is a very active immunological site and plays an essential role in host health, directly interacting with the aquatic environment [6,7]. Fish gut-associated lymphoid tissue (GALT) involves lymphocytes, plasmatic cells, granulocytes, and macrophages [8]. This mucosal surface supports large microbial populations, which play a key role in the intestinal environment and host-microbial interactions. Fish intestinal microbiome comprises complex communities with demonstrated impact on host health, mucosal development and cellular differentiation, metabolism, nutrition, and disease resistance [9]
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