Encapsulation of beneficial probiotic bacteria in extracellular matrix from biofilm-forming Bacillus subtilis

Design of probiotic delivery systems and their therapeutic effects on targeted tissues

The microbiota at different sites in the body is closely related to disease. The intake of probiotics is an effective strategy to alleviate diseases and be adjuvant in their treatment. However, probiotics may suffer from harsh environments and colonization resistance, making it difficult to maintain a sufficient number of live probiotics to reach the target sites and exert their original probiotic effects. Encapsulation of probiotics is an effective strategy. Therefore, probiotic delivery systems, as effective methods, have been continuously developed and innovated to ensure that probiotics are effectively delivered to the targeted site. In this review, initially, the design of probiotic delivery systems is reviewed from four aspects: probiotic characteristics, processing technologies, cell-derived wall materials, and interactions between wall materials. Subsequently, the review focuses on the effects of probiotic delivery systems that target four main microbial colonization sites: the oral cavity, skin, intestine, and vagina, as well as disease sites such as tumors. Finally, this review also discusses the safety concerns of probiotic delivery systems in the treatment of disease and the challenges and limitations of implementing this method in clinical studies. It is necessary to conduct more clinical studies to evaluate the effectiveness of different probiotic delivery systems in the treatment of diseases.

Single-cell encapsulation systems for probiotic delivery: Armor probiotics

Functional foods or drugs based on probiotics have gained unprecedented attention and development due to the increasingly clear relationship between probiotics and human health. Probiotics can regulate intestinal microbiota, dynamically participating in various physiological activities to directly affect human health. Some probiotic-based functional preparations have shown great potential in treating multiple refractory diseases. Currently, the survival and activity of probiotic cells in complex environments in vitro and in vivo have taken priority, and various encapsulation systems based on food-derived materials have been designed and constructed to protect and deliver probiotics. However, traditional encapsulation technology cannot achieve precise protection for a single probiotic, which makes it unable to have a significant effect after release. In this case, single-cell encapsulation systems can be assembled based on biological interfaces to protect and functionalize individual probiotic cells, maximizing their physiological activity. This review discussed the arduous challenges of probiotics in food processing, storage, human digestion, and the commonly used probiotic encapsulation system. Besides, a novel technology of probiotic encapsulation was introduced based on single-cell coating, namely, "armor probiotics". We focused on the classification, structural design, and functional characteristics of armor coatings, and emphasized the essential functional characteristics of armor probiotics in human health regulation, including regulating intestinal health and targeted bioimaging and treatment of diseased tissues. Subsequently, the benefits, limitations, potential challenges, as well as future direction of armor probiotics were put forward. We hope this review may provide new insights and ideas for developing a single-cell probiotics encapsulating system.

Comprehensive efficacy of nano-formulated mixed probiotics on broiler chickens' performance and Salmonella Typhimurium challenge

The increasing recognition of the potential advantages beyond nanoencapsulation of probiotics gained great attention owing to effective properties. Hence, we provided the most in-depth look into the influence of nanoformulated multi strain probiotics; BLB-NPs comprising Bacillus subtilis ATCC19659, Lactobacillus plantarum ATCC8014 and Bifidobacterium bifidum ATCC29521 on growth performance, antioxidant status and intestinal immunity supporting the defense against Salmonella Typhimurium (S. Typhimurium) challenge in broilers chickens. A total of 2,800 one-day-old male Ross 308 boiler chicks were divided into 7 groups; 1 control without additives, 3 probiotics [fed control diets mixed with B. subtilis, L. plantarum and B. bifidum (BLB) at concentrations of 1 × 104 (BLBI), 1 × 106 (BLBII) and 1 × 108 (BLBIII) CFU /kg diet, respectively] and 3 nanoencapsulated probiotics [fed control diets supplemented with BLB loaded nanoparticles (BLB-NPs) at concentrations of 1 × 104 (BLB-NPsI), 1 × 106 (BLB-NPsII) and 1 × 108 (BLB-NPsIII) CFU /kg diet, respectively]. All previous groups were challenged at d 22 of age with S. Typhimurium. Birds fed BLB-NPs II and III exhibited better weight gain and FCR simultaneously with upregulation in nutrients transporters genes (LAT-1, PepT-1, CAT-1 and SGLT1) even after S. Typhimurium challenge. Upregulation of immmune related genes (IL-1β, IL-6, IL-8, MyD88, NF-kB, CCL20, CXCLi2, TLR-2, TLR-4 and SOCS1) was prominently subsided in BLB-NPsIII fed group. The strengthening ability of BLB-NPs for broilers' intestinal barriers was evidenced by augmented expression of JAM, MUC-2, occludin and FABP-2 genes, diminished S. Typhimurium counts and suppressed its virulence related genes (HilA and SopD) with restored histopathological pictures of cecum. Notably, post dietary inclusion of higher levels of BLB-NPsIII, the abundance of beneficial Biofidobacterium and Lactobacillus species was dominated over harmful E. coli ones. Birds fortified with BLB-NPs displayed potent antioxidant potential signified by boosting serum and intestinal antioxidant markers alongside reducing oxidative ones. Overall, the abovementioned positive outcomes of BLB-NPs encouraged their potential application in poultry feed to attain superior performance and elicit protective immunity against S. Typhimurium infection.

Intestinal Delivery of Probiotics: Materials, Strategies, and Applications

Probiotics with diverse and crucial properties and functions have attracted broad interest from many researchers, who adopt intestinal delivery of probiotics to modulate the gut microbiota. However, the major problems faced for the therapeutic applications of probiotics are the viability and colonization of probiotics during their processing, oral intake, and subsequent delivery to the gut. The challenges of simple oral delivery (stability, controllability, targeting, etc.) have greatly limited the use of probiotics in clinical therapies. Nanotechnology can endow the probiotics to be delivered to the intestine with improved survival rate and increased resistance to the adverse environment. Additionally, the progress in synthetic biology has created new opportunities for efficiently and purposefully designing and manipulating the probiotics. In this article, a brief overview of the types of probiotics for intestinal delivery, the current progress of different probiotic encapsulation strategies, including the chemical, physical, and genetic strategies and their combinations, and the emerging single-cell encapsulation strategies using nanocoating methods, is presented. The action mechanisms of probiotics that are responsible for eliciting beneficial effects are also briefly discussed. Finally, the therapeutic applications of engineered probiotics are discussed, and the future trends toward developing engineered probiotics with advanced features and improved health benefits are proposed.

Maize Root Exudates Promote Bacillus sp. Za Detoxification of Diphenyl Ether Herbicides by Enhancing Colonization and Biofilm Formation

Diphenyl ether herbicides are extensively utilized in agricultural systems, but their residues threaten the health of sensitive rotation crops. Functional microbial strains can degrade diphenyl ether herbicides in the rhizosphere of crops, facilitating the restoration of a healthy agricultural environment. However, the interplay between microorganisms and plants in diphenyl ether herbicides degradation remains unclear. Thus, the herbicide-degrading strain Bacillus sp. Za and the sensitive crop, maize, were employed to uncover the interaction mechanism. The degradation of diphenyl ether herbicides by strain Bacillus sp. Za was promoted by root exudates. The strain induced root exudate re-secretion in diphenyl ether herbicide-polluted maize. We further showed that root exudates enhanced the rhizosphere colonization and the biofilm biomass of strain Za, augmenting its capacity to degrade diphenyl ether herbicide. Root exudates regulated gene fliZ, which is pivotal in biofilm formation. Wild-type strain Za significantly reduced herbicide toxicity to maize compared to the ZaΔfliZ mutant. Moreover, root exudates promoted strain Za growth and chemotaxis, which was related to biofilm formation. This mutualistic relationship between the microorganisms and the plants demonstrates the significance of plant-microbe interactions in shaping diphenyl ether herbicide degradation in rhizosphere soils. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Bacillus subtilis SOM8 isolated from sesame oil meal for potential probiotic application in inhibiting human enteropathogens

BACKGROUND

While particular strains within the Bacillus species, such as Bacillus subtilis, have been commercially utilised as probiotics, it is critical to implement screening assays and evaluate the safety to identify potential Bacillus probiotic strains before clinical trials. This is because some Bacillus species, including B. cereus and B. anthracis, can produce toxins that are harmful to humans.

RESULTS

In this study, we implemented a funnel-shaped approach to isolate and evaluate prospective probiotics from homogenised food waste - sesame oil meal (SOM). Of nine isolated strains with antipathogenic properties, B. subtilis SOM8 displayed the most promising activities against five listed human enteropathogens and was selected for further comprehensive assessment. B. subtilis SOM8 exhibited good tolerance when exposed to adverse stressors including acidity, bile salts, simulated gastric fluid (SGF), simulated intestinal fluid (SIF), and heat treatment. Additionally, B. subtilis SOM8 possesses host-associated benefits such as antioxidant and bile salt hydrolase (BSH) activity. Furthermore, B. subtilis SOM8 contains only haemolysin toxin genes but has been proved to display partial haemolysis in the test and low cytotoxicity in Caco-2 cell models for in vitro evaluation. Moreover, B. subtilis SOM8 intrinsically resists only streptomycin and lacks plasmids or other mobile genetic elements. Bioinformatic analyses also predicted B. subtilis SOM8 encodes various bioactives compound like fengycin and lichendicin that could enable further biomedical applications.

CONCLUSIONS

Our comprehensive evaluation revealed the substantial potential of B. subtilis SOM8 as a probiotic for targeting human enteropathogens, attributable to its exceptional performance across selection assays. Furthermore, our safety assessment, encompassing both phenotypic and genotypic analyses, showed B. subtilis SOM8 has a favourable preclinical safety profile, without significant threats to human health. Collectively, these findings highlight the promising prospects of B. subtilis SOM8 as a potent probiotic candidate for additional clinical development.

Exploring the potential of Bacillus subtilis as cell factory for food ingredients and special chemicals

BACKGROUND

Bacillus subtilis has been established as model microorganism for fundamental research in the laboratory on protein production/secretion and sporulation and as model bacterium for controlling spoilage in the food industry. It has also been used for production of (commercial) enzymes and several secondary metabolites such as vitamins. However, this doesn't fully reflect the potential of B. subtilis as a cell-factory. Here, various strains of B. subtilis, including food-grade, spore-deficient strains and industrially used strains, were compared for their growth and metabolic potential. Industry-relevant parameters were analyzed for all strains under various aeration regimes, under anaerobic conditions, in various nutritious and nutrient-limited cultivation media, with and without organic nitrogen sources, and with and without sugar.

RESULTS

Practical experiments were conducted to compare industrial relevant properties like growth rates, intracellular components and extracellular metabolite profile of different B. subtilis strains. Based on growth flexibility in different media, we found that some strains like NCIB3610 and DSM1092 are adapted to inorganic or organic nitrogen source utilization, which is highly relevant when considering a biorefinery approach using various cheap and abundant waste/sidestreams. Secondly, spore-deficient strains such as 3NA, 168 S and PY79S, showed advantages in microbial protein and acetolactate pathway expression, which is associated with applications in food industry for protein supplement and diacetyl production. Lastly, WB800 and PY79S exhibited potential for fermentative production of dipicolinic acid, 2,3-butanediol and lactic acid that could serve as precursors for biopolymers.

CONCLUSION

This study demonstrates the broad potential for more extensive industrial use of Bacillus subtilis in the (bio-based) chemical industry for use of sidestreams, in the personal care industry, in the food industry for food additive production, and in the bio-sustainable industry for biofuel and bio-degradable plastic precursors production. In addition, selecting different B. subtilis strains for specific purposes makes full use of the diversity of this species and increases the potential of B. subtilis in its contribution to the bio-based economy.

Probiotic properties of Bacillus subtilis DG101 isolated from the traditional Japanese fermented food nattō

Spore-forming probiotic bacteria offer interesting properties as they have an intrinsic high stability, and when consumed, they are able to survive the adverse conditions encountered during the transit thorough the host gastrointestinal (GI) tract. A traditional healthy food, nattō, exists in Japan consisting of soy fermented by the spore-forming bacterium Bacillus subtilis natto. The consumption of nattō is linked to many beneficial health effects, including the prevention of high blood pressure, osteoporosis, and cardiovascular-associated disease. We hypothesize that the bacterium B. subtilis natto plays a key role in the beneficial effects of nattō for humans. Here, we present the isolation of B. subtilis DG101 from nattō and its characterization as a novel spore-forming probiotic strain for human consumption. B. subtilis DG101 was non-hemolytic and showed high tolerance to lysozyme, low pH, bile salts, and a strong adherence ability to extracellular matrix proteins (i.e., fibronectin and collagen), demonstrating its potential application for competitive exclusion of pathogens. B. subtilis DG101 forms robust liquid and solid biofilms and expresses several extracellular enzymes with activity against food diet-associated macromolecules (i.e., proteins, lipids, and polysaccharides) that would be important to improve food diet digestion by the host. B. subtilis DG101 was able to grow in the presence of toxic metals (i.e., chromium, cadmium, and arsenic) and decreased their bioavailability, a feature that points to this probiotic as an interesting agent for bioremediation in cases of food and water poisoning with metals. In addition, B. subtilis DG101 was sensitive to antibiotics commonly used to treat infections in medical settings, and at the same time, it showed a potent antimicrobial effect against pathogenic bacteria and fungi. In mammalians (i.e., rats), B. subtilis DG101 colonized the GI tract, and improved the lipid and protein serum homeostasis of animals fed on the base of a normal- or a deficient-diet regime (dietary restriction). In the animal model for longevity studies, Caenorhabditis elegans, B. subtilis DG101 significantly increased the animal lifespan and prevented its age-related behavioral decay. Overall, these results demonstrate that B. subtilis DG101 is the key component of nattō with interesting probiotic properties to improve and protect human health.

Minicell-forming Escherichia coli mutant with increased chemical production capacity and tolerance to toxic compounds

Minicell, a small spherical form of bacterium produced by abnormal fission, possesses cytoplasmic constituents similar to those of the parental cell, except for genomic DNA. E. coli strains were engineered to produce minicells and value-added chemicals. Minicell-forming mutants showed enhanced tolerance to toxic chemicals and a higher intracellular NADH/NAD⁺ ratio than the wild-type. When toxic chemicals such as isobutanol, isobutyraldehyde, and isobutyl acetate were produced in this mutant, the titers increased by 67 %, 175 %, and 214 %, respectively. In addition, morphological changes and membrane dispersion mechanisms in minicell-forming mutants improved lycopene production by 259 %. This increase in production capacity was more pronounced when biomass hydrolysate was used as the substrate. Isobutanol and lycopene production also increased by 92 % and 295 %, respectively, on using the substrate in the mutant. It suggests that minicell-forming mutants are an excellent platform for biochemical production.

Biofilm-based delivery approaches and specific enrichment strategies of probiotics in the human gut

The use of probiotics has been one of the effective strategies to restructure perturbed human gut microbiota following a disease or metabolic disorder. One of the biggest challenges associated with the use of probiotic-based gut modulation strategies is to keep the probiotic cells viable and stable during the gastrointestinal transit. Biofilm-based probiotics delivery approaches have emerged as fascinating modes of probiotic delivery in which probiotics show significantly greater tolerance and biotherapeutic potential, and interestingly probiotic biofilms can be developed on food-grade surfaces too, which is ideal for the growth and proliferation of bacterial cells for incorporation into food matrices. In addition, biofilms can be further encapsulated with food-grade materials or with bacterial self-produced biofilms. This review presents a newly emerging and unprecedently discussed techniques for the safe delivery of probiotics based on biofilms and further discusses newly emerging prebiotic materials which target specific gut microbiota groups for growth and proliferation.

An open-source computational tool for measuring bacterial biofilm morphology and growth kinetics upon one-sided exposure to an antimicrobial source

Bacillus subtilis biofilms are well known for their complex and highly adaptive morphology. Indeed, their phenotypical diversity and intra-biofilm heterogeneity make this gram-positive bacterium the subject of many scientific papers on the structure of biofilms. The “robustness” of biofilms is a term often used to describe their level of susceptibility to antimicrobial agents and various mechanical and molecular inhibition/eradication methods. In this paper, we use computational analytics to quantify Bacillus subtilis morphological response to proximity to an antimicrobial source, in the form of the antiseptic chlorhexidine. Chlorhexidine droplets, placed in proximity to Bacillus subtilis macrocolonies at different distances result in morphological changes, quantified using Python-based code, which we have made publicly available. Our results quantify peripheral and inner core deformation as well as differences in cellular viability of the two regions. The results reveal that the inner core, which is often characterized by the presence of wrinkled formations in the macrocolony, is more preserved than the periphery. Furthermore, the paper describes a crescent-shaped colony morphology which occurs when the distance from the chlorhexidine source is 0.5 cm, as well as changes observed in the growth substrate of macrocolonies exposed to chlorhexidine.

Novel nano-encapsulated probiotic agents: Encapsulate materials, delivery, and encapsulation systems

Gut microbes are closely associated with most human health. When ingested orally, probiotics can effectively regulate the composition and quantity of human intestinal microorganisms, which is beneficial to human health. However, probiotics will be affected by the harsh environment of the digestive tract during the in vivo transportation process, and ensuring the viability of probiotics is a great challenge. Probiotic encapsulating technology provides an effective solution to this problem. The introduction of extreme temperatures, large probiotic microcapsule sizes and the difficulty in controlling probiotic microcapsule particle sizes mean that traditional microcapsule encapsulation methods have some limitations. From traditional microcapsule technology to the bulk encapsulation of probiotics with nanofibers and nanoparticles to the recent ability to wear nano "armor" for a single probiotic through biofilm, biological membrane and nanocoating. Emerging probiotic nanoagents provides a new conceptual and development direction for the field of probiotic encapsulation. In this review, we presented the characteristics of encapsulated probiotic carrier materials and digestive tract transport systems, we focused on the encapsulation systems of probiotic nanoagents, we analyzed the shortcomings and advantages of the current agent encapsulation systems, and we stated the developmental direction and challenges for these agents for the future.

Effects of Bacillus subtilis BS-Z15 on Intestinal Microbiota Structure and Body Weight Gain in Mice

In our previous study, we identified a metabolite of Bacillus subtilis BS-Z15 (a strain with probiotic characteristics) that could improve immunity in mice. In the present study, we examined the effects of B. subtilis BS-Z15 and its metabolites on body weight gain and the intestinal microbiota of mice. Sixty 25-day-old male Kunming white mice were selected and randomly divided into four groups: control group (A), daily saline gavage; B. subtilis-treated group (B), single gavage (1 × 10⁹ CFU/time/animal/day); group D, 14 consecutive gavages (1 × 10⁹ CFU/time/animal/day); and B. subtilis metabolite-treated group (E), 30 consecutive gavages (90 mg kg^-1/time/animal/day). High-throughput sequencing technology was used to analyze intergroup differences in the mouse intestinal microbiota. The results showed that the three treated groups had significantly slower body weight gain compared with the control group, which lasted until the 45 days (P < 0.05), and the daily food intake of the treated mice was higher (P < 0.05). The intestinal microbiota structure of the mice in the treated groups was significantly altered compared with that in the control group, suggesting that B. subtilis BS-Z15 may regulate the weight gain of animals by affecting their intestinal bacterial composition. After stopping the gavage of B. subtilis BS-Z15, the abundance of this strain in the small intestine of the mice gradually decreased and its presence was undetectable at 45 days, indicating that B. subtilis BS-Z15 could not colonize the intestine of these mice. These findings suggest that B. subtilis BS-Z15 may regulate intestinal microbiota through its metabolites to reduce weight gain.

The potential role of adherence factors in probiotic function in the gastrointestinal tract of adults and pediatrics: a narrative review of experimental and human studies

Numerous studies point to the important role of probiotic bacteria in gastrointestinal health. Probiotics act through mechanisms affecting enteric pathogens, epithelial barrier function, immune signaling, and conditioning of indigenous microbiota. Once administered, probiotics reach the gastrointestinal tract and interact with the host through bacterial surface molecules, here called adhesion factors, which are either strain- or specie-specific. Probiotic adhesion, through structural adhesion factors, is a mechanism that facilitates persistence within the gastrointestinal tract and triggers the initial host responses. Thus, an understanding of specific probiotic adhesion mechanisms could predict how specific probiotic strains elicit benefits and the potential of adherence factors as a proxy to predict probiotic function. This review summarizes the present understanding of probiotic adherence in the gastrointestinal tract. It highlights the bacterial adhesion structure types, their molecular communication with the host and the consequent impact on intestinal diseases in both adult and pediatric populations. Finally, we discuss knockout/isolation studies as direct evidence for adhesion factors conferring anti-inflammatory and pathogen inhibition properties to a probiotic.What is known: Probiotics can be used to treat clinical conditions.Probiotics improve dysbiosis and symptoms.Clinical trials may not confirm in vitro and animal studies.What is new: Adhesion structures may be important for probiotic function.Need to systematically determine physical characteristics of probiotics before selecting for clinical trials.Probiotics may be genetically engineered to add to clinical efficacy.

Chickpea-Derived Prebiotic Substances Trigger Biofilm Formation by Bacillus subtilis

Chickpea-based foods are known for their low allergenicity and rich nutritional package. As an essential dietary legume, chickpea is often processed into milk or hummus or as an industrial source of protein and starch. The current study explores the feasibility of using the chickpea-derived prebiotic substances as a scaffold for growing Bacillus subtilis (a prospective probiotic bacterium) to develop synbiotic chickpea-based functional food. We report that the chickpea-derived fibers enhance the formation of the B. subtilis biofilms and the production of the antimicrobial pigment pulcherrimin. Furthermore, electron micrograph imaging confirms the bacterial embedding onto the chickpea fibers, which may provide a survival tactic to shield and protect the bacterial population from environmental insults. Overall, it is believed that chickpea-derived prebiotic substances provide a staple basis for developing functional probiotics and synbiotic food.

Antibiofilm and antioxidant activity of Rosmarinus officinalis essential oil

The aim of the work was to explore the antioxidant potential and antibiofilm activity of the Rosmarinus officinalis essential oil. The DPPH method was used to determine the antioxidant activity. The agar microdilution method was used to determine the minimum biofilm inhibiting concentration (MBIC). The MALDI-TOF MS Biotyper was used to evaluate the antibiofilm activity on the wood and glass surface. Vapor phase antimicrobial analysis was used to determine the effect on the food model. The antioxidant activity was 28.76 % ± 2.68 %. The MBIC for Stenotrophomonas maltophilia was 25 µL.mL-1 and for Bacillus subtilis 12.5 µL.mL-1. Analysis of the mass spectra of S. maltophilia revealed an inhibitory effect from the 5th, which persisted until the end of the experiment. Analysis of the mass spectra of B. subtilis showed an inhibitory effect from the 7th of the experiment. The experiments showed an effect on both tested surfaces. The food model showed a more pronounced effect of the Rosmarinus officinalis essential oil against B. subtilis. We assume that the effect of the essential oil is to disrupt the polysaccharide structure of the biofilm and consequently reduce the resistance of the biofilm. We have established that MALDI-TOF MS Biotyper is a suitable tool for evaluating changes in biofilm structure and could find more significant application for the study of biofilms in food and clinical practice.

Bacillus subtilis biofilm formation and social interactions

Biofilm formation is a process in which microbial cells aggregate to form collectives that are embedded in a self-produced extracellular matrix. Bacillus subtilis is a Gram-positive bacterium that is used to dissect the mechanisms controlling matrix production and the subsequent transition from a motile planktonic cell state to a sessile biofilm state. The collective nature of life in a biofilm allows emergent properties to manifest, and B. subtilis biofilms are linked with novel industrial uses as well as probiotic and biocontrol processes. In this Review, we outline the molecular details of the biofilm matrix and the regulatory pathways and external factors that control its production. We explore the beneficial outcomes associated with biofilms. Finally, we highlight major advances in our understanding of concepts of microbial evolution and community behaviour that have resulted from studies of the innate heterogeneity of biofilms.

Biofilm formation onto starch fibres by Bacillus subtilis governs its successful adaptation to chickpea milk

Beneficial biofilms may confer effective adaptation to food matrices that assist bacteria in enduring hostile environmental conditions. The matrices, for instance, dietary fibres of various food products, might serve as a natural scaffold for bacterial cells to adhere and grow as biofilms. Here, we report on a unique interaction of Bacillus subtilis cells with the resistant starch fibresof chickpea milk (CPM), herein CPM fibres, along with the production of a reddish-pink pigment. Genetic analysis identified the pigment as pulcherrimin, and also revealed the involvement of Spo0A/SinI pathway in modulating the observed phenotypes. Besides, through successful colonization of the CPM fibres, the wild-type cells of B. subtilis displayed enhanced survivability and resilience to environmental stress, such as heat and in vitro gastrointestinal treatments. In total, we infer that the biofilm formation on CPM fibres is an adaptation response of B. subtilis for strategic survival.

The Evolution of Human Probiotics: Challenges and Prospects

In recent years, the intestinal microbiota has been found to greatly influence a number of biological processes important for human health and longevity. Microbial composition changes easily in response to external factors, such as an unbalanced diet, lack of physical activity, and smoking. Probiotics are a key factor in maintaining the optimal composition of the intestinal microbiota. However, a number of important questions related to probiotics, such as indication for prescription, comparative efficacy of monostrain and multistrain probiotics, methods of delivery, and shelf life, remain unresolved. The aim of this review is to highlight existing issues regarding probiotic production and their prescription. The review presents the most recent findings regarding advantages and efficacy of monostrain and multistrain probiotics, preservation of probiotic strains in capsules and microcapsules, production of probiotics in the form of biofilms for improved efficacy and survival, and results of clinical studies evaluating the benefits of probiotics against different pathologies. We believe that this work will be of interest to physicians and researchers alike and will promote the development of new probiotics and ensuing regimens aimed at the treatment of various diseases.

Bacillus subtilis-Based Probiotic Improves Skeletal Health and Immunity in Broiler Chickens Exposed to Heat Stress

Simple Summary

High ambient temperature is a major environmental stressor affecting the physiological and behavioral status of animals, increasing stress susceptibility and immunosuppression, and consequently increasing intestinal permeability (leaky gut) and related neuroinflammation. Probiotics, as well as prebiotics and synbiotics, have been used to prevent or decrease stress-associated detrimental effects on physiological and behavioral homeostasis in humans and various animals. The current data indicate that a dietary probiotic supplement, Bacillus subtilis, reduces heat stress-induced abnormal behaviors and negative effects on skeletal health in broilers through a variety of cellular responses, regulating the functioning of the microbiota–gut–brain axis and/or microbiota-modulated immunity during bone remodeling under thermoneutral and heat-stressed conditions.

Abstract

The elevation of ambient temperature beyond the thermoneutral zone leads to heat stress, which is a growing health and welfare issue for homeothermic animals aiming to maintain relatively constant reproducibility and survivability. Particularly, global warming over the past decades has resulted in more hot days with more intense, frequent, and long-lasting heat waves, resulting in a global surge in animals suffering from heat stress. Heat stress causes pathophysiological changes in animals, increasing stress sensitivity and immunosuppression, consequently leading to increased intestinal permeability (leaky gut) and related neuroinflammation. Probiotics, as well as prebiotics and synbiotics, have been used to prevent or reduce stress-induced negative effects on physiological and behavioral homeostasis in humans and various animals. The current data indicate dietary supplementation with a Bacillus subtilis-based probiotic has similar functions in poultry. This review highlights the recent findings on the effects of the probiotic Bacillus subtilis on skeletal health of broiler chickens exposed to heat stress. It provides insights to aid in the development of practical strategies for improving health and performance in poultry.

Role of Probiotic Bacilli in Developing Synbiotic Food: Challenges and Opportunities

The human body is inhabited by a vast diversity of probiotic microorganisms that could positively affect human physiology. Besides, prebiotic food substances may induce symbiotic relationship among probiotic species through the successful establishment of commensal microbiota, whose connections with the host are multifaceted and multidirectional. As deliberated throughout this review, prebiotic and synbiotic foods contain the capability to stimulate numerous health characteristics in host organisms through various means. Predominantly, the normal microbiota fosters the digestion of food and may boost the innate and adaptive immune system’s functionalities. Therefore, live probiotic bacteria, for instance, probiotic Bacilli obtained together with prebiotic food, can help stimulate healthiness in humans. Thus, we discuss how certain dietary fibers may preserve the probiotic efficacy by serving as the scaffold for probiotic Bacilli to colonize them through forming symbiotic interactions. The fibers can essentially promote protection by encapsulating probiotic Bacilli against various environmental and physical stresses that might kill the free-living bacterial cells. Besides, these fibers would serve as prebiotic substances that would eventually be utilized for the proliferation of probiotic cells. It is believed that applying this conceptual idea will provide a novel platform toward developing probiotic and synbiotic foods, as discussed in this review.

Bacillus subtilis natto as a potential probiotic in animal nutrition

The growing global demand for animal products and processed meat has created a challenge for the livestock sector to enhance animal productivity without compromising product quality. The restriction of antibiotics in animal feeds as growth promoters makes the use of probiotics a natural and safe alternative to obtain functional foods that provide animal health and quality and to maintain food safety for consumers. To incorporate these additives into the diet, detailed studies are required, in which in vitro and in vivo assays are used to prove the efficacy and to ensure the safety of probiotic candidate strains. Studies on the use of Bacillus subtilis natto as a spore-forming probiotic bacterium in animal nutrition have shown no hazardous effects and have demonstrated the effectiveness of its use as a probiotic, mainly due to its proven antimicrobial, anti-inflammatory, antioxidant, enzymatic, and immunomodulatory activity. This review summarizes the recent scientific background on the probiotic effects of B. subtilis natto in animal nutrition. It focuses on its safety assessment, host-associated efficacy, and industrial requirements.

Hemolysin BL from novel Bacillus toyonensis BV-17 induces antitumor activity both in vitro and in vivo

The gut microbiota plays an important role in cancer development and immunotherapy. Bacterial toxins have enormous antitumor potential due to their cytotoxicity and ability to activate the immune system. Using 16S rRNA gene sequencing, we compared the gut microbiota composition of fecal samples from healthy individuals and patients with colorectal cancer (CRC) and observed that the genus Bacillus was common in the healthy donors but was absent in the CRC patients. Further, we isolated a novel Bacillus toyonensis BV-17 from the fecal samples of the healthy individuals. Our results showed that the supernatant of the Bacillus toyonensis BV-17 cultures could quickly kill various tumor cell lines within minutes in vitro, by causing cell membrane disruption, blebbing, and leakage of cytoplasmic content. Fast protein liquid chromatography (FPLC) and mass spectrometry analysis identified hemolysin BL (HBL) as the effector molecule, which exhibits a different cytotoxicity mechanism compared to previous studies. Intra-tumor injection of low dose HBL inhibited the growth of both treated and untreated tumors in mice. The outcomes of this pioneer study suggest that HBL exhibits antitumor activity and is a potential chemotherapeutic agent that could be engineered to target only tumor cells in future.

Safety assessment of Streptococcus thermophilus IDCC 2201 used for product manufacturing in Korea

Safety evaluation of probiotics has become increasingly important for human consumption in food industry. The aims of this study were to assess safety of Streptococcus thermophilus IDCC 2201 through in vitro and in vivo tests. In results, this strain was found to be negative for hemolytic and β-glucuronidase activity. In addition, thermophilus IDCC 2201 was susceptible to nine antibiotics suggested by EFSA. In accordance with MIC tests, whole-genome analysis indicated that S. thermophilus IDCC 2201 neither harbors antibiotic resistance nor toxigenic genes. Furthermore, none of the biogenic amines including tyramine and histamine was produced and negligible amounts of D-lactate were produced by S. thermophilus IDCC 2201. Finally, it was confirmed that there was no mortality and toxicity throughout single-dose oral toxicity tests in rats. Therefore, we report that S. thermophilus IDCC 2201 is considered to be safe for human consumption as probiotics.

The Stress-Responsive Alternative Sigma Factor SigB of Bacillus subtilis and Its Relatives: An Old Friend With New Functions

Alternative sigma factors have led the core RNA polymerase (RNAP) to recognize different sets of promoters to those recognized by the housekeeping sigma A-directed RNAP. This change in RNAP promoter selectivity allows a rapid and flexible reformulation of the genetic program to face environmental and metabolic stimuli that could compromise bacterial fitness. The model bacterium Bacillus subtilis constitutes a matchless living system in the study of the role of alternative sigma factors in gene regulation and physiology. SigB from B. subtilis was the first alternative sigma factor described in bacteria. Studies of SigB during the last 40 years have shown that it controls a genetic universe of more than 150 genes playing crucial roles in stress response, adaption, and survival. Activation of SigB relies on three separate pathways that specifically respond to energy, environmental, and low temperature stresses. SigB homologs, present in other Gram-positive bacteria, also play important roles in virulence against mammals. Interestingly, during recent years, other unexpected B. subtilis responses were found to be controlled by SigB. In particular, SigB controls the efficiencies of spore and biofilm formation, two important features that play critical roles in adaptation and survival in planktonic and sessile B. subtilis communities. In B. subtilis, SigB induces the expression of the Spo0E aspartyl-phosphatase, which is responsible for the blockage of sporulation initiation. The upregulated activity of Spo0E connects the two predominant adaptive pathways (i.e., sporulation and stress response) present in B. subtilis. In addition, the RsbP serine-phosphatase, belonging to the energy stress arm of the SigB regulatory cascade, controls the expression of the key transcription factor SinR to decide whether cells residing in the biofilm remain in and maintain biofilm growth or scape to colonize new niches through biofilm dispersal. SigB also intervenes in the recognition of and response to surrounding microorganisms, a new SigB role that could have an agronomic impact. SigB is induced when B. subtilis is confronted with phytopathogenic fungi (e.g., Fusarium verticillioides) and halts fungal growth to the benefit of plant growth. In this article, we update and review literature on the different regulatory networks that control the activation of SigB and the new roles that have been described the recent years.

Biofilm Matrixome: Extracellular Components in Structured Microbial Communities

Biofilms consist of microbial communities embedded in a 3D extracellular matrix. The matrix is composed of a complex array of extracellular polymeric substances (EPS) that contribute to the unique attributes of biofilm lifestyle and virulence. This ensemble of chemically and functionally diverse biomolecules is termed the 'matrixome'. The composition and mechanisms of EPS matrix formation, and its role in biofilm biology, function, and microenvironment are being revealed. This perspective article highlights recent advances about the multifaceted role of the 'matrixome' in the development, physical-chemical properties, and virulence of biofilms. We emphasize that targeting biofilm-specific conditions such as the matrixome could lead to precise and effective antibiofilm approaches. We also discuss the limited knowledge in the context of polymicrobial biofilms, and the need for more in-depth analyses of the EPS matrix in mixed communities that are associated with many human infectious diseases.

Role of Bacillus species in biofilm persistence and emerging antibiofilm strategies in the dairy industry

Biofilm-forming Bacillus species are often involved in persistent contamination and spoilage of dairy products. They therefore present a major microbiological challenge in the field of dairy food quality and safety. Due to their substantial physiological versatility, Bacillus species can survive in various parts of dairy manufacturing plants, leading to a high risk of product spoilage and potential dissemination of foodborne diseases. Furthermore, biofilm and heat-resistant spore formation make these bacteria challenging to eliminate. Thus, some strategies have been employed to remove, prevent, or delay the formation of Bacillus biofilms in the dairy industry, but with limited success. Lack of understanding of the Bacillus biofilm structure and behavior in conditions relevant to dairy-associated environments could partially account for this situation. The current paper reviews dairy-associated biofilm formation by Bacillus species, with particular attention to the role of biofilm in Bacillus species adaptation and survival in a dairy processing environment. Relevant model systems are discussed for the development of novel antimicrobial approaches to improve the quality of dairy food. © 2020 Society of Chemical Industry.

Delivery to the gut microbiota: A rapidly proliferating research field

The post genomic era has brought breakthroughs in our understanding of the complex and fascinating symbiosis we have with our co-evolving microbiota, and its dramatic impact on our physiology, physical and mental health, mood, interpersonal communication, and more. This fast "proliferating" knowledge, particularly related to the gut microbiota, is leading to the development of numerous technologies aimed to promote our health via prudent modulation of our gut microbiota. This review embarks on a journey through the gastrointestinal tract from a biomaterial science and engineering perspective, and focusses on the various state-of-the-art approaches proposed in research institutes and those already used in various industries and clinics, for delivery to the gut microbiota, with emphasis on the latest developments published within the last 5 years. Current and possible future trends are discussed. It seems that future development will progress toward more personalized solutions, combining high throughput diagnostic omic methods, and precision interventions.

Probiotic Bifunctionality of Bacillus subtilis-Rescuing Lactic Acid Bacteria from Desiccation and Antagonizing Pathogenic Staphylococcus aureus

Live probiotic bacteria obtained with food are thought to have beneficial effects on a mammalian host, including their ability to reduce intestinal colonization by pathogens. To ensure the beneficial effects, the probiotic cells must survive processing and storage of food, its passage through the upper gastrointestinal tract (GIT), and subsequent chemical ingestion processes until they reach their target organ. However, there is considerable loss of viability of the probiotic bacteria during the drying process, in the acidic conditions of the stomach, and in the high bile concentration in the small intestine. Bacillus subtilis, a spore-forming probiotic bacterium, can effectively maintain a favorable balance of microflora in the GIT. B. subtilis produces a protective extracellular matrix (ECM), which is shared with other probiotic bacteria; thus, it was suggested that this ECM could potentially protect an entire community of probiotic cells against unfavorable environmental conditions. Consequently, a biofilm-based bio-coating system was developed that would enable a mutual growth of B. subtilis with different lactic acid bacteria (LAB) through increasing the ECM production. Results of the study demonstrate a significant increase in the survivability of the bio-coated LAB cells during the desiccation process and passage through the acidic environment. Thus, it provides evidence about the ability of B. subtilis in rescuing the desiccation-sensitive LAB, for instance, Lactobacillus rhamnosus, from complete eradication. Furthermore, this study demonstrates the antagonistic potential of the mutual probiotic system against pathogenic bacteria such as Staphylococcus aureus. The data show that the cells of B. subtilis possess robust anti-biofilm activity against S. aureus through activating the antimicrobial lipopeptide production pathway.