Lyophilized B. subtilis ZB183 Spores: 90-Day Repeat Dose Oral (Gavage) Toxicity Study in Wistar Rats

Engineered Bacillus subtilis as Oral Probiotics To Enhance Clearance of Blood Lactate

Elevated lactate concentrations are implicated in various acute and chronic diseases, such as sepsis and mitochondrial dysfunction, respectively. Conversely, ineffective lactate clearance is associated with poor clinical prognoses and high mortality in these diseases. While several groups have proposed using small molecule inhibitors and enzyme replacement to reduce circulating lactate, there are few practical and effective ways to manage this condition. Recent evidence suggests that lactate is exchanged between the systemic circulation and the gut, allowing bidirectional modulation between the gut microbiota and peripheral tissues. Inspired by these findings, this work seeks to engineer spore-forming probiotic Bacillus subtilis strains to enable intestinal delivery of lactate oxidase as a therapeutic enzyme. After strain optimization, we showed that oral administration of engineered B. subtilis spores to the gut of mice reduced the level of blood lactate in two different mouse models involving exogenous challenge or pharmacologic perturbation without disrupting gut microbiota composition, liver function, or immune homeostasis. Taken together, through the oral delivery of engineered probiotic spores to the gastrointestinal tract, our proof-of-concept study offers a practical strategy to aid in the management of disease states with elevated blood lactate and provides a new approach to "knocking down" circulating metabolites to help understand their roles in host physiological and pathological processes.

Bacillus subtilis ZB423: 90-Day repeat dose oral (gavage) toxicity study in Wistar rats

The novel genetically modified probiotic Bacillus subtilis ZB423 was assessed in a 90-day repeated-dose oral toxicity study adhering to Good Laboratory Practice (GLP) and Organization for Economic Cooperation and Development (OECD) guidelines. Spray-dried spores at a concentration of 1.1E12 CFU/g were administered at doses of 130, 260, and 519 mg/kg body weight/day correlating to 1.43 × 1011, 2.86 × 1011, and 5.71 × 1011 CFU/kg/day, respectively, by oral gavage to Wistar rats for a period of 90 consecutive days. Results showed no toxicologically relevant findings for B. subtilis ZB423 from measured parameters. The no observed adverse effect level (NOAEL) of B. subtilis ZB423 is 519 mg/kg body weight/day corresponding to 5.71 × 1011 CFU/kg/day for lyophilized B. subtilis ZB423 spores under the test conditions employed.

Engineering a probiotic Bacillus subtilis for acetaldehyde removal: A hag locus integration to robustly express acetaldehyde dehydrogenase

We have addressed critical challenges in probiotic design to develop a commercially viable bacterial strain capable of removing the intestinal toxin, acetaldehyde. In this study, we report the engineering of the hag locus, a σD-dependent flagellin expression site, as a stable location for robust enzyme production. We demonstrate constitutive gene expression in relevant conditions driven by the endogenous hag promoter, following a deletion of the gene encoding a post-translational regulator of σD, FlgM, and a point mutation to abrogate the binding of the translational inhibitor CsrA. Reporter constructs demonstrate activity at the hag locus after germination, with a steady increase in heterologous expression throughout outgrowth and vegetative growth. To evaluate the chassis as a spore-based probiotic solution, we identified the physiologically relevant ethanol metabolic pathway and the subsequent accumulation of gut-derived acetaldehyde following alcohol consumption. We integrated a Cupriavidus necator aldehyde dehydrogenase gene (acoD) into the hag locus under the control of the flagellin promoter and observed a rapid reduction in acetaldehyde levels in gut-simulated conditions post-germination. This work demonstrates a promising approach for the development of genetically engineered spore-based probiotics.

Living Engineered Bacterial Therapeutics: Emerging Affordable Precision Interventions

Live biotherapeutic products (LBPs), including engineered bacteria, are rapidly emerging as potential therapeutic interventions. These innovative therapies can serve as live in situ drug delivery platforms for the direct deposition of therapeutic payloads, including complex biologics, at sites of disease. This approach offers a platform likely to enhance therapeutic efficacy and decrease off-target side effects. LBPs also can likely be distributed at a relatively low price point, as their production can be economically scaled up. LBPs represent an exciting new means for ensuring healthy lives and promoting well-being for all ages, aligning with the World Health Organization's sustainable development goal 3.

Engineered Bacillus subtilis as oral probiotics to enhance clearance of blood lactate

Elevated lactate concentrations are implicated in various acute and chronic diseases such as sepsis and mitochondrial dysfunction, respectively. Conversely, ineffective lactate clearance is associated with poor clinical prognoses and high mortality in these diseases. While several groups have proposed using small molecule inhibitors and enzyme replacement to reduce circulating lactate, there are few practical and effective ways to manage this condition. Recent evidence suggests that lactate is exchanged between systemic circulation and the gut, allowing bidirectional modulation between the gut microbiota and peripheral tissues. Inspired by these findings, this work seeks to engineer spore-forming probiotic B. subtilis strains to enable intestinal delivery of lactate oxidase as a therapeutic enzyme. After strain optimization, we showed that oral administration of engineered B. subtilis spores to the gut of mice reduced elevations in blood lactate in two different mouse models involving exogenous challenge or pharmacologic perturbation without disrupting gut microbiota composition, liver function, or immune homeostasis. Taken together, through the oral delivery of engineered probiotic spores to the gastrointestinal tract, our proof-of-concept study offers a practical strategy to aid in the management of disease states with elevated blood lactate and provides a new approach to 'knocking down' circulating metabolites to help understand their roles in host physiological and pathological processes.

Next generation probiotics: Engineering live biotherapeutics

The population dynamics of the human microbiome have been associated with inflammatory bowel disease, cancer, obesity, autoimmune diseases, and many other human disease states. An emerging paradigm in treatment is the administration of live engineered organisms, also called next-generation probiotics. However, the efficacy of these microbial therapies can be limited by the organism's overall performance in the harsh and nutrient-limited environment of the gut. In this review, we summarize the current state of the art use of bacterial and yeast strains as probiotics, highlight the recent development of genetic tools for engineering new therapeutic functions in these organisms, and report on the latest therapeutic applications of engineered probiotics, including recent clinical trials. We also discuss the supplementation of prebiotics as a method of manipulating the microbiome and improving the overall performance of engineered live biotherapeutics.

Subchronic oral toxicity assessment of Bacillus velezensis strain BV379 in sprague-dawley rats

INTRODUCTION

The spore-forming bacterial species Bacillus velezensis is commonly utilized in feed for livestock and aquaculture. In recent years, there has been increased interest in introducing B. velezensis into human supplements and food. Before it can be safely administered in humans, the safety of each B. velezensis strain needs to be established. The objective of this study was to evaluate the in vivo safety of Bacillus velezensis strain BV379 by high-dose oral administration to rats in a 28-day subchronic toxicity study.

METHODS

In this study, 80 animals were assigned to four groups: vehicle control, 1 × 1010, 4 × 1010, or 10 × 1010 CFU/kg bw/day by gavage. The following toxicological assessments were performed: ophthalmological examinations; observations for viability, signs of gross toxicity, and behavioral changes; in-life parameters, including body weight and food consumption; urinalysis, hematology, clinical chemistry, and coagulation assessments; macroscopic and microscopic tissue assessments; and bacterial enumeration in selected tissues.

RESULTS

Under the conditions of this study, no adverse clinical endpoints were attributed to the administration of Bacillus velezensis strain BV379, which was well-tolerated up to the highest dose of 10 × 1010 CFU/kg bw/day.

CONCLUSION

These results support the in vivo pre-clinical safety of Bacillus velezensis strain BV379 for use in food and supplements.

Engineering bacteria to modulate host metabolism

The microbial community of the gut, collectively termed the gut microbiota, modulates both host metabolism and disease development in a variety of clinical contexts. The microbiota can have detrimental effects and be involved in disease development and progression, but it can also offer benefits to the host. This has led in the last years to the development of different therapeutic strategies targeting the microbiota. In this review, we will focus on one of these strategies that involve the use of engineered bacteria to modulate gut microbiota in the treatment of metabolic disorders. We will discuss the recent developments and challenges in the use of these bacterial strains with an emphasis on their use for the treatment of metabolic diseases.

Engineered probiotics

Engineered probiotics are a kind of new microorganisms produced by modifying original probiotics through gene editing. With the continuous development of tools and technology progresses, engineering renovation of probiotics are becoming more diverse and more feasible. In the past few years there have been some advances in the development of engineered probiotics that will benefit humankind. This review briefly introduces the theoretical basis of gene editing technology and focuses on some recent engineered probiotics researches, including inflammatory bowel disease, bacterial infection, tumor and metabolic diseases. It is hoped that it can provide help for the further development of genetically modified microorganisms, stimulate the potential of engineered probiotics to treat intractable diseases, and provide new ideas for the diagnosis of some diseases or some industrial production.