Beneficial Shifts in the Gut Bacterial Community of Gilthead Seabream (Sparus aurata) Juveniles Supplemented with Allium-Derived Compound Propyl Propane Thiosulfonate (PTSO)

Abstract

This study analyzes the potential use of an Allium-derived compound, propyl propane thiosulfonate (PTSO), as a functional feed additive in aquaculture. Gilthead seabream (Sparus aurata) juveniles had their diet supplemented with this Allium-derived compound (150 mg/kg of PTSO) and were compared with control fish. The effects of this organosulfur compound were tested by measuring the body weight and analyzing the gut microbiota after 12 weeks. The relative abundance of potentially pathogenic Vibrio and Pseudomonas in the foregut and hindgut of supplemented fish significantly decreased, while potentially beneficial Lactobacillus increased compared to in the control fish. Shannon's alpha diversity index significantly increased in both gut regions of fish fed with a PTSO-supplemented diet. Regarding beta diversity, significant differences between treatments only appeared in the hindgut when minority ASVs were taken into account. No differences occurred in body weight during the experiment. These results indicate that supplementing the diet with Allium-derived PTSO produced beneficial changes in the intestinal microbiota while maintaining the productive parameters of gilthead seabream juveniles.

Keywords: Allium-based phytogenic; Sparus aurata; body weight; gilthead seabream; gut microbiota; propyl propane thiosulfonate.

Figure 1

LDA effect size (LEfSe) analyses showing bacterial classes and genera that differed significantly between control fish and those supplemented with Allium-derived PTSO in the foregut and hindgut. Significant LDA score > 4.0. Sample size was 48 for control foregut, 55 for control hindgut, 42 for Allium-supplemented foregut, and 51 for Allium-supplemented hindgut.

Figure 2

Bar plot summarizing the relative bacterial abundance at the genus level in different gut regions (foregut and hindgut) and treatments. Control (C) refers to gilthead seabream juveniles fed with basal diet while Allium-derived PTSO (T) refers to experimental gilthead seabream juveniles fed with basal diet supplemented with Allium-derived PTSO. Sample size was 48 for control foregut, 55 for control hindgut, 42 for Allium-supplemented foregut, and 51 for Allium-supplemented hindgut.

Figure 3

(A) Shannon’s diversity index and (B) ASV richness (number of bacterial ASV) of bacterial community of foregut and hindgut of gilthead seabream juveniles fed with control (blue) and Allium supplemented diets (red). Sample size was 48 for control foregut, 55 for control hindgut, 42 for Allium-supplemented foregut, and 51 for Allium-supplemented hindgut.

Figure 4

Principal coordinate analysis based on (A) weighted and (B) unweighted UniFrac distance matrices exploring the effects in the bacterial gut community of the supplementation with Allium-derived PTSO in the diet of gilthead seabream juveniles (red: foregut—control fish; pink: hindgut—control; green: foregut—treated fish; light green: hindgut—treated fish). Percentages show the proportion of variance explained by each axis. Sample size was 48 for control foregut, 55 for control hindgut, 42 for Allium-supplemented foregut, and 51 for Allium-supplemented hindgut.

Figure 5

Body weight (g) of control (red) and Allium-derived PTSO (blue) supplemented gilthead bream juveniles during the 12 weeks experiment. Whiskers show ± 95% confidence intervals.