Bacillus velezensis HBXN2020 alleviates Salmonella Typhimurium-induced colitis by improving intestinal barrier integrity and reducing inflammation

  1. Linkang Wang
  2. Haiyan Wang
  3. Xinxin Li
  4. Mengyuan Zhu
  5. Dongyang Gao
  6. Dayue Hu
  7. Zhixuan Xiong
  8. Xiangmin Li
  9. Ping Qian

  • Curated by eLife

    eLife logo

    eLife assessment

    In this useful study, Wang and colleagues investigate the potential probiotic effects of Bacillus velezensis to prevent colitis in a mouse model. They provide solid evidence that B. velezensis limits the growth of Salmonella typhimurium in lab culture and in mice, together with beneficial effects on the microbiota. The work will be of interest to infectious disease researchers and those studying the microbiome.

Reviewed by

Read the full article See related articles

Listed in

Log in to save this article

Abstract

Bacillus velezensis is a species of Bacillus that has been widely investigated because of its broad-spectrum antimicrobial activity. However, most studies on Bacillus velezensis have focused on the biocontrol of plant diseases, with few reports on antagonizing Salmonella Typhimurium infections. In this investigation, it was discovered that Bacillus velezensis HBXN2020, which was isolated from healthy black pigs, possessed strong anti-stress and broad-spectrum antibacterial activity. Importantly, Bacillus velezensis HBXN2020 did not cause any adverse side effects in mice when administered at various doses (1 × 10 7 , 1 × 10 8 , and 1 × 10 9 CFU) for 14 d. Supplementing Bacillus velezensis HBXN2020 spores, either as a curative or preventive measure, dramatically reduced the levels of Salmonella Typhimurium ATCC14028 in the mice’s feces, ileum, cecum, and colon, as well as the disease activity index (DAI), in a model of colitis caused by this pathogen in mice. Additionally, supplementing Bacillus velezensis HBXN2020 spores significantly regulated cytokine levels (TNF-α, IL-1β, IL-6, and IL-10) and maintained the expression of tight junction proteins and mucin protein. Most importantly, adding Bacillus velezensis HBXN2020 spores to the colonic microbiota improved its homeostasis and increased the amount of beneficial bacteria ( Lactobacillus and Akkermansia ). All together, Bacillus velezensis HBXN2020 can improve intestinal microbiota homeostasis and gut barrier integrity and reduce inflammation to help treat bacterial colitis.

Article activity feed

  1. Version published to 10.1101/2023.11.21.568052v2 on bioRxiv
  2. Version published to 10.7554/elife.93423 on eLife
  3. Version published to 10.7554/elife.93423.1 on eLife
  4. eLife

    eLife assessment

    In this useful study, Wang and colleagues investigate the potential probiotic effects of Bacillus velezensis to prevent colitis in a mouse model. They provide solid evidence that B. velezensis limits the growth of Salmonella typhimurium in lab culture and in mice, together with beneficial effects on the microbiota. The work will be of interest to infectious disease researchers and those studying the microbiome.

  5. eLife

    Reviewer #1 (Public Review):

    Summary:

    Wang and colleagues presented an investigation of pig-origin bacteria Bacillus velezensis HBXN2020, for its released genome sequence, in vivo safety issue, probiotic effects in vitro, and protection against Salmonella infection in a murine model. Various techniques and assays are performed.

    Strengths:

    An extensive study on the probiotic properties of the Bacillus velezensis strain HBXN2020.

    Weaknesses:

    - The main results are all descriptive, without new insight advancing the field or a mechanistic understanding of the observed protection.

    - Most of the results and analysis parts are separated without a link or any story-telling to deliver a concise message.

    - For the Salmonella Typhimurium-induced mouse model of colitis, it is not clear how an oral infection of C57BL/6 would lead to colitis. Streptomycin is always pretreated (https://link.springer.com/protocol/10.1007/978-1-0716-1971-1_17).

  6. eLife

    Reviewer #2 (Public Review):

    Summary:

    In this study, Wang and colleagues study the potential probiotic effects of Bacillus velezensis. Bacillus species have the potential benefit of serving as probiotics due to their ability to form endospores and synthesize secondary metabolites. B. velezensis has been shown to have probiotic effects in plants and animals but data for human use are scarce, particularly with respect to salmonella-induced colitis. In this work, the authors identify a strain of B. velezensis and test it for its ability to control colitis in mice.

    Key findings:

    (1) The authors sequence an isolate for B. velezensis - HBXN2020 and describe its genome (roughly 4 mb, 46% GC-content etc).

    (2) The authors next describe the growth of this strain in broth culture and survival under acid and temperature stress. The susceptibility of HBXN2020 was tested against various antibiotics and against various pathogenic bacteria. In the case of the latter, the authors set out to determine if HBXN2020 could directly inhibit the growth of pathogenic bacteria. Convincing data, indicating that this is indeed the case, are presented.

    (3) To determine the safety profile of BHXN2020 (for possible use as a probiotic), the authors infected the strain in mice and monitored weight, together with cytokine profiles. Infected mice displayed no significant weight loss and expression of inflammatory cytokines remained unchanged. Blood cell profiles of infected mice were consistent with that of uninfected mice. No significant differences in tissues, including the colon were observed.

    (4) Next, the authors tested the ability of HBXN2020 to inhibit the growth of Salmonella typhimurium (STm) and demonstrate that HBXN2020 inhibits STm in a dose-dependent manner. Following this, the authors infect mice with STm to induce colitis and measure the ability of HBXN2020 to control colitis. The first outcome measure was a reduction in STm in faeces. Consistent with this, HBXN2020 reduced STm loads in the ileum, cecum, and colon. Colon length was also affected by HBXN2020 treatment. In addition, treatment with HBXN2020 reduced the appearance of colon pathological features associated with colitis, together with a reduction in inflammatory cytokines.

    (5) After noting the beneficial (and anti-inflammatory effects) of HBXN2020, the authors set out to investigate the effects on microbiota during treatment. Using a variety of algorithms, the authors demonstrate that upon HXBN2020 treatment, microbiota composition is restored to levels akin to that seen in healthy mice.

    (6) Finally, the authors assessed the effect of using HBXN2020 as prophylactic treatment for colitis by first treating mice with the spores and then infecting them with STm. Their data indicate that treatment with HBXN2020 reduced colitis. A similar beneficial impact was seen with the gut microbiota.

    Strengths:

    (1) Good use of in vitro and animal models to demonstrate a beneficial probiotic effect.

    (2) Most observations are supported using multiple approaches.

    (3) The mouse experiments are very convincing.

    Weaknesses:

    (1) Whilst a beneficial effect is observed, there is no investigation of the mechanism that underpins this.

    (2) The mouse experiments would have benefited from the use of standard anti-inflammatory therapies to control colitis. That way the authors could compare their approach of using bacillus spores with the current gold standard for treatment.

  7. eLife

    Reviewer #3 (Public Review):

    Summary:
    The manuscript by Wang et al. investigates the effects of B. velezensis HBXN2020 in alleviating S. Typhimurium-induced mouse colitis. The results showed that B. velezensis HBXN2020 could alleviate bacterial colitis by enhancing intestinal homeostasis (decreasing harmful bacteria and enhancing the abundance of Lactobacillus and Akkermansia) and gut barrier integrity and reducing inflammation. Overall, the manuscript is of potential interest to readers.

    Strengths:
    B. velezensis HBXN2020 is a novel species of Bacillus that can produce a great variety of secondary metabolites and exhibit high antibacterial activity against several pathogens. B. velezensis HBXN2020 is able to form endospores and has strong anti-stress capabilities. B. velezensis HBXN2020 has a synergistic effect with other beneficial microorganisms, which can improve intestinal homeostasis.

    Weaknesses:
    There are few studies about the clinical application of Bacillus velezensis. Thus, more studies are still needed to explore the effectiveness of Bacillus velezensis before clinical application.

  8. Version published to 10.1101/2023.11.21.568052v1 on bioRxiv