Dietary supplementation with probiotics regulates gut microbiota structure and function in Nile tilapia exposed to aluminum.

Qixiao Zhai,Hao Zhang,Ruipeng Yu,Leilei Yu,Wei Chen,Nanzhen Qiao,Jianxin Zhao,Fengwei Tian,Tianqi Li

doi:10.7717/peerj.6963

Abstract

Backgrounds and aimsAluminum contamination of water is becoming increasingly serious and threatens the health status of fish. Lactobacillus plantarum CCFM639 was previously shown to be a potential probiotic for alleviation aluminum toxicity in Nile tilapia. Considering the significant role of the gut microbiota on fish health, it seems appropriate to explore the relationships among aluminum exposure, probiotic supplementation, and the gut microbiota in Nile tilapia and to determine whether regulation of the gut microbiota is related to alleviation of aluminum toxicity by a probiotic in Nile tilapia.Methods and resultsThe tilapia were assigned into four groups, control, CCFM639 only, aluminum only, and aluminum + CCFM639 groups for an experimental period of 4 weeks. The tilapia in the aluminum only group were grown in water with an aluminum ion concentration of 2.73 mg/L. The final concentration of CCFM639 in the diet was 108 CFU/g. The results show that environmental aluminum exposure reduced the numbers of L. plantarum in tilapia feces and altered the gut microbiota. As the predominant bacterial phyla in the gut, the abundances of Bacteroidetes and Proteobacteria in aluminum-exposed fish were significantly elevated and lowered, respectively. At the genus level, fish exposed to aluminum had a significantly lower abundance of Deefgea, Plesiomonas, and Pseudomonas and a greater abundance of Flavobacterium, Enterovibrio, Porphyromonadaceae uncultured, and Comamonadaceae. When tilapia were exposed to aluminum, the administration of a probiotic promoted aluminum excretion through the feces and led to a decrease in the abundance of Comamonadaceae, Enterovibrio and Porphyromonadaceae. Notably, supplementation with a probiotic only greatly decreased the abundance of Aeromonas and Pseudomonas.ConclusionAluminum exposure altered the diversity of the gut microbiota in Nile tilapia, and probiotic supplementation allowed the recovery of some of the diversity. Therefore, regulation of gut microbiota with a probiotic is a possible mechanism for the alleviation of aluminum toxicity in Nile tilapia.

Highlights

Aluminum, the third commonest chemical element and the most abundant metal on earth, is ubiquitous in the environment
The aim of the study was to explore whether the regulation of gut microbiota is an aluminum toxicity alleviation mechanism exerted by probiotics in tilapia
The accumulated aluminum in Nile tilapia can be excreted through feces, and oral administration of L. plantarum CCFM639 increased aluminum excretion (Fig. 6)

Summary

Introduction

The third commonest chemical element and the most abundant metal on earth, is ubiquitous in the environment. Environmental aluminum levels have increased due to diverse anthropogenic activities such as water treatment, eutrophic lakes control, mining operations, and industrial landfill (Fernandez-Davila et al, 2012; Garcia-Medina et al, 2011). The aluminum level reaches 5.7 mg/L in certain rivers and lakes in England, the United States, China, and Brazil (Camargo, Fernandes & Martinez, 2009; Da Cruz et al, 2015), research has been shown that concentration of aluminum ranging from 0.1 to 0.2 mg/L can be harmful to fish (Baker & Schofield, 1982; Wang et al, 2013). Excess aluminum ions in water were reported to cause mortalities and decreasing population of Atlantic salmon in Norway, southeast Canada, and the northeastern United States (Monette & McCormick, 2008). Aluminum contamination causes economic losses in aquaculture and poses potential human health risks from consumption of aquatic products

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