Probiotic Bacillus pumilus SE5 shapes the intestinal microbiota and mucosal immunity in grouper Epinephelus coioides

Abstract

The health benefits of probiotics are thought to occur, at least in part, through an improved intestinal microbial balance in fish, although the molecular mechanisms whereby probiotics modulate the intestinal microbiota by means of activation of mucosal immunity are rarely explored. In this study, the effects of viable and heat-inactivated probiotic Bacillus pumilus SE5 on the intestinal dominant microbial community and mucosal immune gene expression were evaluated. The fish were fed for 60 d with 3 different diets: control (without probiotic), and diets T1 and T2 supplemented with 1.0 × 10⁸ cells g⁻¹ viable and heat-inactivated B. pumilus SE5, respectively. Upregulated expression of TLR1, TLR2 and IL-8, but not MyD88 was observed in fish fed the viable probiotic, while elevated expression of TLR2, IL-8 and TGF-β1, but not MyD88 was observed in fish fed the heat-inactivated B. pumilus SE5. The induced activation of intestinal mucosal immunity, especially the enhanced expression of antibacterial epinecidin-1, was consistent with the microbial data showing that several potentially pathogenic bacterial species such as Psychroserpens burtonensis and Pantoea agglomerans were suppressed by both the viable and heat-inactivated probiotic B. pumilus SE5. These results lay the foundation for future studies on the molecular interactions between probiotics, intestinal microbiota and mucosal immunity in fish.

Effect of dietary supplementation with a synbiotic (Lacto Forte) on growth performance, haematological and histological profiles, the innate immune response and resistance to bacterial disease inOreochromis niloticus

“…This lack of difference was probably due to the short period of supplementation, which was insufficient to activate innate immune pathways. It has been proposed that probiotic bacteria, the main components of synbiotics, can interact with some pattern recognition receptors (PRRs), such as Toll‐like receptors (TLRs), and upregulate specific cytokines, thereby exaggerating the fish immune response (Yang et al, ). Recently, evidence of cell recognition by mannose‐binding lectin (MBL) following synbiotic supplementation has also been reported (Arockiaraj et al, ).…”

“…The health benefits of these compounds are mediated by competition with pathogenic bacteria and balancing of the indigenous microbiota in the gastrointestinal tract (Rengpipat, ), improvements in water quality and feed efficiency and reductions in fish waste (Ngan & Phu, ; Nimrat, Suksawat, Boonthai, & Vuthiphandchai, ). In addition, these compounds increase intestinal mucosal adhesion (Servin & Coconnier, ), activate mucus production, and increase microvillus density, in turn producing impenetrable barriers against invading pathogens (Standen et al, ; Yang, Xia, Ye, Zou, & Sun, ).…”

Antioxidant Properties of Probiotic Bacteria

“…Bacillus species are preferred in the feed industry because of their stability as spore-forming bacteria and ability to produce a variety of enzymes such as protease, amylase, and lipase [34]. The intestinal microbiota and mucosal immunity of fish could be shaped by Bacillus [35], and the mucosal immunity of chickens could also be improved via Bacillus treatment [36]. …”

The positive contributions of PowerLac ™ supplementation to the production performance, feed utilization and disease resistance of Nile tilapia Oreochromis niloticus (L.)

“…,b), and nutrient uptake and utilization by means of (1) contribution of digestive enzymes (Yanbo & Zirong ; Suzer, Çoban, Kamaci, Saka, Firat, Otgucuoğlu & Küçüksari ; Yang et al . ), (2) modulation of intestinal microbiota (Yang, Xia, Ye, Zou & Sun ), (3) contribution on the development of digestive tract morphology (an increase in microvilli) that allows higher surface area for nutrient uptake (Frouël, Le Bihan, Serpentini, Lebel, Koueta & Nicolas ; Sáenz de Rodrigáñez, Díaz‐Rosales, Chabrillón, Smidt, Arijo, León‐Rubio, Alarcon, Balebona, Moriñigo, Cara & Moyano ), and (4) stimulation of enzyme activity related to nutrient utilization, such as those involved in nutrient absorption in the intestinal brush border (alkaline phosphatase and leucine aminopeptidase) (Sáenz de Rodrigáñez et al . ; Panigrahi, Kiron, Satoh & Watanabe ).…”

“…The advantageous effects of PowerLac TM on the growth and feed conversion ratio of Nile tilapia might be explained by the established positive role of probiotics vis-a-vis the targeted species, including the improvement on feed digestibility (Dawood et al 2015a,b), and nutrient uptake and utilization by means of (1) contribution of digestive enzymes (Yanbo & Zirong 2006;Suzer, C ßoban, Kamaci, Saka, Firat, Otgucuo glu & K€ uc ߀ uksari 2008;Yang et al 2015), (2) modulation of intestinal microbiota (Yang, Xia, Ye, Zou & Sun 2014), (3) contribution on the development of digestive tract morphology (an increase in microvilli) that allows higher surface area for nutrient uptake ( Figure 4 Survival of Nile tilapia (Oreochromis niloticus) fed with a practical diet containing different PowerLac TM supplementation levels (0 g kg À1 ; 0.25 g kg À1 ; 0.50 g kg À1 and 1.00 g kg À1 ) and postchallenged with Aeromonas hydrophila (10 6 cell mL À1 , 2 weeks). Different letters in each bar indicate significant difference (P < 0.05).…”