The Effects of Nisin-Producing Lactococcus lactis Strain Used as Probiotic on Gilthead Sea Bream (Sparus aurata) Growth, Gut Microbiota, and Transcriptional Response

Abstract

The present research tested the effects of dietary nisin-producing Lactococcus lactis on growth performance, feed utilization, intestinal morphology, transcriptional response, and microbiota in gilthead sea bream (Sparus aurata). A feeding trial was conducted with fish weighting 70–90 g. Fish were tagged with passive, integrated transponders and distributed in nine 500 L tanks with 40 fish each. Fish were fed for 12 weeks with either a control (diet A) or experimental diets (diets B and C) in triplicate (3 tanks/diet). Extruded pellets of diets B and C were supplemented with a low (2 × 109 CFU/kg) and a high (5 × 109 CFU/kg) dose of probiotic, respectively. No significant differences were found between groups for the feed conversion ratio or specific growth rates. However, the final body weight of fish fed diet C was significantly higher than the control group with intermediate values for fish fed diet B. Histological analysis conducted using a semi-quantitative scoring system showed that probiotic did not alter the morphology of the intestine and did not trigger inflammation. With regard to the transcriptomic response, a customized PCR array layout was designed to simultaneously profile a panel of 44 selected genes. Significant differences in the expression of key genes involved in innate and acquired immunity were detected between fish fed probiotic and control diets. To analyze the microbiota associated to the feeds and the gut autochthonous microbial communities, we used the Illumina MiSeq platform for sequencing the 16S rRNA gene and a metagenomics pipeline based on VSEARCH and RDP databases. The analysis of gut microbiota revealed a lack of colonization of the probiotic in the host’s intestinal mucosa. However, probiotic did modulate the fish gut microbiota, confirming that colonization is not always necessary to induce host modification. In fact, diets B and C were enriched with Actinomycetales, as compared to diet A, which instead showed a higher percentage of Pseudomonas, Sphyngomonas, and Lactobacillus genera. These results were confirmed by the clear separation of gut bacterial community of fish fed with the probiotic from the bacterial community of control fish group in the beta-diversity and PLS-DA (supervised partial least-squares discriminant analysis) analyses.

Vibriosis Outbreaks in Aquaculture: Addressing Environmental and Public Health Concerns and Preventive Therapies Using Gilthead Seabream Farming as a Model System

“…Probiotics can be defined as live bacterial species able to survive and thrive in the acidic gastric environment whose activity leads to a beneficial effect on the health of the host by re-establishing or improving the gut microbiota, when administered in adequate amounts (Zhou et al, 2020 ; Moroni et al, 2021 ), although less stringent definitions have been proposed (see Borges et al, 2021 ). Probiotics are ideally inoffensive and promote host fitness.…”

Modulation of Gilthead Sea Bream Gut Microbiota by a Bioactive Egg White Hydrolysate: Interactions Between Bacteria and Host Lipid Metabolism

“…In other studies of this special issue of nutrition and gut microbiota in aquaculture, we also analyzed the effect of probiotics and alternative FM replacers on gilthead sea bream gut microbiota (Moroni et al, 2021;Solé-Jiménez et al, 2021). Meanwhile, bioactive peptides derived from food proteins are considered important modulators of various biological processes, which occur both systemically and locally within the gastrointestinal tract (Moughan et al, 2014).…”

Anti-nodavirus potential activity of R.A73 Enterococcus faecium strain, isolated from Tunisian freshwater fish mucus

“…On the other hand, the assessment of gene expression coding for the chemokine receptor C-C chemokine receptor 3 (CCR3) from cells inoculated with R.A73 E. faecium showed increased expression of the CCR3. In previous study, the probiotic treatment altered markers such as CCR3, resulting in an overall increase in gene expression, which was particularly noticeable in sh fed diets (Moroni et al, 2021).…”