Influence of dietary supplementation with Bacillus velezensis on intestinal microbial diversity of mice

Highlights

• Yaks are aboriginal breed of the Qinghai-Tibet plateau (3000 m) which are highly adaptable to cold and hypoxic environments.

• Hypoxia and hypothermia may induce special intestinal microflora in yaks.

• B. velezensis supplementation increased the population of Lactobacillus & Ruminococcus in the duodenum & C.Arthromitus in the jejunum.

Abstract

Yaks are an aboriginal breed of the Qinghai-Tibet plateau (3000 m), which are highly adaptable to cold and hypoxic environments. It is noticed that hypoxia and hypothermia can induce changes in intestinal microbial structure in animals. Increasing evidences suggested that probiotics supplementation can improve the balance of gut microbiota of animals. However, so far, very few studies have emphasized on the probiotics isolated from yaks in the Qinghai-Tibet Plateau. Therefore, a potential probiotic strain Bacillus velezensis was isolated from yaks. In the present study, a total of 18 Kunming mice (15–18 g) were equally distributed into two groups; control and probiotic treated groups (1 × 10⁹ CFU/day). During the experimental period, all the mice from both groups were given standard normal diet ad libitum. At the end of the experiment, mice were euthanized and the intestines (duodenum, jejunum, ileum, and cecum) were removed for high-throughput sequencing. The results demonstrated that Bacillus velezensis supplementation showed beneficial effects on the gut microbiota of mice. Specifically, Bacillus velezensis supplementation increased the population of Lactobacillus and Ruminococcus in the duodenum, and Candidatus Arthromitus in the jejunum. Additionally, Acinetobacter in the duodenum and Helicobacter in the cecum were decreased after feeding Bacillus velezensis. Altogether, these findings suggested that Bacillus velezensis isolated from Tibetan yaks can improve gut microbiota of mice.

Introduction

The outbreaks of bacterial disease cause a significant reduction of fertility, milk production and weight gain in animals, which have led huge economic losses to the livestock industry [1,2]. Antibiotics are widely used to treat bacterial diseases and improve the growth performance of animals [3]. However, it was no longer recommended now, because the potential risk to human health and microflora balance has become a common concern [4]. Not only that, the misuse of antibiotics can accelerate the development of bacterial resistance and lead to antibacterial-associated diarrhea (AAD) [5]. Therefore, it is an entire need to find a new antibiotic alternative as soon as possible. Now a days, many scholars believe that one of the optimal alternatives to antibiotics is probiotics [6].

Probiotics are living microorganisms that can benefit the host if given in enough amounts, meanwhile it does not pollute the environment [7]. There are large number of microorganisms colonizing the intestines of animals and play a significant role in the health of the host. Numerous studies have found that gut microbiota is closely related to digestive absorption, immunomodulation, metabolism, and the development of nervous system [8,9]. Instead, imbalance of gut microbiota may induce constipation, enteritis, and obesity [10]. Studies in recent years have shown that alteration of gut microbiota is intimately linked to diabetes and even tumors [11]. It is very important for the healthy development of the host to maintain the stability of gut microbiota. Probiotics supplementation not only improve the growth performance but also maintain the balance of intestinal microbes as compared to antibiotics [12,13]. Significantly, supplementing with probiotics can also lower cholesterol, prevent diarrhea, enhance the body immunity and resistance in organisms against diseases [14,15].

Yaks are an aboriginal breed of the high-altitude hypoxic environment of Qinghai-Tibet Plateau (above 3000 m). The necessities of life of Tibetan herdsmen cannot be separated from yaks. Yaks are important source of milk, meat, leather and play vital role in economic source for local herdsmen. Previous studies indicated that oxygen-deficient environment and dietary habit can lead to changes in the structure of gut microbes [16]. Yaks have resided the Qinghai-Tibet Plateau over thousands of years and they have completely adapted to the local extremely severe survival environment. Therefore, the extreme environment in Tibet may induce yaks to have special intestinal microbial structure. However, until now, few studies have focused on the probiotic potential of Bacillus velezensis isolated from Tibetan yaks. Therefore, the present study is designed to assess whether Bacillus velezensis isolated from Tibetan yaks have an ameliorative and protective role on the gut microbiota of mice.