Bacillus subtilis inhibition of enterotoxic Escherichia coli-induced activation of MAPK signaling pathways in Caco-2 cells

Distinct effects of mucin on phage-host interactions in model systems of beneficial and pathogenic bacteria

Phage-host interactions that occur in host-associated microbiomes are influenced by a plethora of environmental factors. Mucins are glycoproteins that represent the main component of mucus, which is found in the animal digestive tract and on the surface of certain organs, serving as the first line of defense against toxins and pathogens. Previous studies have shown that lytic phages have an important influence on the microbial composition in mucosal areas. Our study expands this knowledge to interactions between previously untested lytic phages targeting probiotic and pathogenic bacteria, as well as temperate phages targeting probiotic bacteria. These interactions could be important in shaping microbial communities and affecting the well-being of their host. This study demonstrates that mucins enhance the adherence of Vibrio anguillarum lytic phages and Bacillus subtilis lytic and temperate phages, as well as B. subtilis and V. anguillarum cells, to solid surfaces. Our results also show that mucins positively affect the attachment of B. subtilis cells even in the presence of phages. This positive effect was not observed in the case of V. anguillarum. This suggests that mucin may shield certain bacteria from phage infections. We also found that mucin influenced the metabolic activity of the two tested bacterial species differently, with strong positive effects on V. anguillarum but not on B. subtilis. This work supports previous findings that phages adhere efficiently to mucus and extends these studies to include other beneficial and pathogenic bacterial species. It also reveals that mucins have different effects on phage-host interactions in different phage-host systems, which may have implications for phage therapies or probiotic treatment strategies.

L-Alanine promotes anti-infectious properties of Bacillus subtilis S-2 spores via the germination receptor gerAA

Bacillus species, which have two cell-type forms (vegetative cells and spores), demonstrate a variety of probiotic functions in animal feed additives and human nutrition. We previously found that the probiotic effect of Bacillus subtilis S-2 spores with high germination response to L-alanine was specifically enhanced by the L-alanine pretreatment. The germination response of Bacillus is highly associated with the germination receptors of spores. However, how L-alanine-induced germination of spores exerts anti-infectious effect in epithelial cells remains unclear. In this study, we constructed the mutant strain of B. subtilis S-2 with germination receptor gerAA knockout to further explore the role of spore germination in resisting pathogen infection to cells. The differential probiotic effects of B. subtilis S-2 and S-2ΔgerAA spores pretreated with L-alanine were evaluated in intestinal porcine epithelial cells (IPEC-J2) or Caco2 cells infected with enterotoxigenic Escherichia coli (ETEC) or following IL-1β stimulation. The results showed that the germination response of the S-2ΔgerAA spores to L-alanine was significantly reduced. Compared with the S-2ΔgerAA spores, the L-alanine-induced germination of B. subtilis S-2 spores significantly increased the activity of anti-adhesion of ETEC to IPEC-J2 cells and reduced the expression of inflammatory factors and cell receptors. L-alanine induction also significantly promoted the expression of autophagy-related proteins in the B. subtilis S-2 spores. These findings demonstrate that the gerAA germination receptor is essential for the probiotic function of Bacillus spores and that L-alanine treatment promotes the anti-infectious properties of the germinated spores in porcine intestinal epithelial IPEC-J2 cells. The result suggests the importance of germination receptor gerAA in helping spore germination and enhancing anti-infectious activity. The findings in the study benefit to screening of potential Bacillus probiotics and increasing probiotic efficacy induced by L-alanine as an adjuvant.

Probiotic performance of B. subtilis MS. 45 improves aquaculture of rainbow trout Oncorhynchus mykiss during acute hypoxia stress

The aim of this study was to produce mutant strains of Bacillus subtilis with high probiotic performance for use in the aquaculture of rainbow trout Oncorhynchus mykiss. The main strain of B. subtilis (MS) was irradiated with gamma rays (5.3 KGy). Subsequently, the B. subtilis mutant strain no. 45 (MS. 45) was selected for bacterial growth performance, resistance to acidic conditions, resistance to bile salts and antibacterial activity against Aeromonas hydrophila and Pseudomonas fluorescens. After 60 days, the rainbow trout (70.25 ± 3.89 g) fed with MS. 45 and MS were exposed to hypoxia stress (dissolved oxygen = 2 ppm). Subsequently, immune indices (lysozyme, bacterial activity and complement activity), hematological indices [hematocrit, hemoglobin, WBC, RBC, mean corpuscular volume (MCV)] and antioxidant factors (T-AOC, SOD and MDA)) were analyzed after and before hypoxia exposure. The expression of immunological genes (IFN-γ, TNF-α, IL-1β, IL-8) in the intestine and the expression of hypoxia-related genes (HIF-1α, HIF-2α, FIH1) in the liver were compared between the different groups under hypoxia and normoxia conditions. Growth, immunological and antioxidant indices improved in group MS. 45 compared to the other groups. Stress indices and associated immunologic and hypoxia expressions under hypoxia and normoxia conditions improved in MS. 45 compared to the other groups. This resulted in improved growth, immunity and stress responses in fish fed with the microbial supplement of MS. 45 (P < 0.05) under hypoxia and normoxia conditions, (P < 0.05), resulting in a significant improvement in trout aquaculture.

Protective Effects of Bacillus subtilis HH2 against Oral Enterotoxigenic Escherichia coli in Beagles

This study evaluated the protective effect of Bacillus subtilis HH2 on beagles orally challenged with enterotoxigenic Escherichia coli (ETEC). We assessed the physiological parameters and the severity of diarrhea, as well as the changes in three serum immunoglobulins (IgG, IgA, and IgM), plasma diamine oxidase (DAO), D-lactate (D-LA), and the fecal microbiome. Feeding B. subtilis HH2 significantly reduced the severity of diarrhea after the ETEC challenge (p < 0.05) and increased serum levels of IgG, IgA, and IgM (p < 0.01). B. subtilis HH2 administration also reduced serum levels of DAO at 48 h after the ETEC challenge (p < 0.05), but no significant changes were observed in D-LA (p > 0.05). Oral ETEC challenge significantly reduced the richness and diversity of gut microbiota in beagles not pre-fed with B. subtilis HH2 (p < 0.05), while B. subtilis HH2 feeding and oral ETEC challenge significantly altered the gut microbiota structure of beagles (p < 0.01). Moreover, 14 days of B. subtilis HH2 feeding reduced the relative abundance of Deinococcus-Thermus in feces. This study reveals that B. subtilis HH2 alleviates diarrhea caused by ETEC, enhances non-specific immunity, reduces ETEC-induced damage to the intestinal mucosa, and regulates gut microbiota composition.

Autoclaved Diet with Inactivated Spores of Bacillus spp. Decreased Reproductive Performance of Muc2−/− and Muc2+/− Mice

Simple Summary

Within barrier facilities for the housing of laboratory animals, the sterilization of feed, bedding, and cages is used to reduce contact with bacteria. However, in nature, animals come into contact with a lot of bacteria. We investigated the effect of an autoclaved diet on the reproductive performance of Muc2^−/− mice. Muc2^−/− mice develop intestinal barrier defects and are sensitive to changes of the gut microbiota. We have shown that the autoclaved diet negatively affects the reproductive performance of Muc2^−/− females and their healthy Muc2^+/− siblings. Thus, the autoclaved diet led to earlier rectal prolapse of Muc2^−/− females combined with intestinal inflammation, compared to mice fed with the non-autoclaved diet. We hypothesize that this effect is due to the reduction of the diet nutritional value and inactivation of Bacillus spp. spores in the autoclaved diet.

Abstract

Within barrier facilities, autoclaved diet and bedding are used for husbandry of laboratory rodents. Bacillus spp. are ubiquitous in nature and some of them are known as probiotics. Inactivation of the Bacillus spores and reduction of the diet nutritional value due to autoclavation could be especially critical for immunodeficient mice. We studied the effect of the autoclaved and non-autoclaved diets on the reproductive performance and the age of prolapse manifestation in Muc2^−/− mice with impaired gut barrier function and, therefore, sensitive to change of microbiota. We found that the non-autoclaved diet led to enhancement of the fertility index of Muc2^−/− and Muc2^+/− female mice. The non-autoclaved diet affected the prolapse of Muc2^−/− mice that occurred later in comparison with females eating the autoclaved diet. We showed that Bacillus spp. was present in the non-autoclaved diet and feces of mice on the non-autoclaved diet. Bacterial strains of the non-autoclaved diet and feces belonged to B. amyloliquefaciens, B. thuringiensis, B. subtilis, Lysinibacillus macrolides, B. cereus, and other representatives of Bacillus spp. Moreover, autoclavation of the diet affected on the percent of the blood and spleen immune cells, the bacterial composition of the intestine, and increased the level of methionine in the thigh muscle of mice. Enhanced reproductive performance and delayed prolapse manifestation in Muc2^−/− mice could be due to improved digestion, as Bacillus spp. from diet and feces had enzymatic activity.

The Application of Bacillus subtilis for Adhesion Inhibition of Pseudomonas and Preservation of Fresh Fish

Inhibiting the growth of spoilage bacteria, such as Pseudomonas spp., is key to reducing spoilage in fish. The mucus adhesion test in vitro showed that the adhesion ability of Bacillus subtilis was positively correlated with its inhibition ability to Pseudomonas spp. In vivo experiments of tilapia showed that dietary supplementation with B. subtilis could reduce the adhesion and colonization of Pseudomonas spp. in fish intestines and flesh, as well as reduce total volatile basic nitrogen (TVB-N) production. High throughput and metabolomic analysis showed treatment with B. subtilis, especially C6, reduced the growth of Pseudomonas spp., Aeromonas spp., Fusobacterium spp., and Enterobacterium spp., as well as aromatic spoilage compounds associated with these bacteria, such as indole, 2,4-bis(1,1-dimethylethyl)-phenol, 3-methyl-1-butanol, phenol, and 1-octen-3-ol. Our work showed that B. subtilis could improve the flavor of fish by changing the intestinal flora of fish, and it shows great promise as a microecological preservative.

Bacillus subtilis extracellular polymeric substances conditioning layers inhibit Escherichia coli adhesion to silicon surfaces: A potential candidate for interfacial antifouling additives

Biofouling on material surfaces is a ubiquitous problem in a variety of fields. In aqueous environments, the process of biofouling initiates with the formation of a layer of macromolecules called the conditioning layer on the solid-liquid interface, followed by the adhesion and colonization of planktonic bacteria and the subsequent biofilm development and maturation. In this study, the extracellular polymeric substances (EPS) secreted by Bacillus subtilis were collected and used to prepare conditioning layers on inert surfaces. The morphologies and antifouling performances of the EPS conditioning layers were investigated. It was found that the initial adhesion of Escherichia coli was inhibited on the surfaces precoated with EPS conditioning layers. To further explore the underlying antifouling mechanisms of the EPS conditioning layers, the respective roles of two constituents of B. subtilis EPS (γ-polyglutamic acid and surfactin) were investigated. This study has provided the possibility of developing a novel interfacial antifouling additive with the advantages of easy preparation, nontoxicity, and environmental friendliness.

Functional in vitro screening of probiotic strains for inoculation of piglets as a prophylactic measure towards Enterotoxigenic Escherichia coli infection

Enterotoxigenic Escherichia coli (ETEC), being the major cause of post-weaning diarrhoea (PWD) in newly weaned piglets, induces poor performance and economic losses in pig production. This functional in vitro screening study investigated probiotic strains for use in suckling piglets as a prophylactic strategy towards PWD. Nine strains were evaluated based on their ability to: enhance intestinal epithelial barrier function, reduce adherence of ETEC F18 to intestinal cells, inhibit growth of ETEC F18, and grow on porcine milk oligosaccharides. Strains included in the screening were of the species Lactobacillus, Enterococcus, Bifidobacterium and Bacillus. Our in vitro screening demonstrated genus-, species and strain-specific differences in the mode of action of the tested probiotic strains. Some of the tested bifidobacteria were able to grow on the two porcine milk oligosaccharides, 3'-sialyllactose sodium salt (3'SL) and Lacto-N-neotetraose (LNnT), whereas most lactic acid bacteria strains and both Bacillus subtilis strains failed to do so. All probiotic strains inhibited growth of ETEC F18 on agar plates. All but the bifidobacteria reduced binding of ETEC F18 to Caco-2 cell monolayers, with the Enterococcus faecium strain having the most profound effect. All three lactic acid bacteria and Bifidobacterium animalis subsp. lactis counteracted the ETEC F18-induced permeability across Caco-2 cell monolayers with the E. faecium strain exhibiting the most pronounced protective effect. The findings from this in vitro screening study indicate that, when selecting probiotic strains for suckling piglets as a prophylactic strategy towards PWD, it would be advantageous to choose a multi-species product including strains with different modes of action in order to increase the likelihood of achieving beneficial effects in vivo.

Cytotoxicity, apoptosis, and IL-8 gene expression induced by some foodborne pathogens in presence of Bacillus coagulans in HT-29 cells

Food poisoning caused by bacteria is one of the most important concerns in food hygiene. The use of probiotics in prevention, control, and treatment of these infections has been considerably increased in recent years. This study evaluated the effect of B. coagulans cell free supernatant (CFS) on growth of Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, non-pathogenic Escherichia coli, and Escherichia coli 0157:H7 by the broth dilution method. The cytotoxicity, and apoptosis induced by pathogens alone and in co-culture with B. coagulans or its CFS were measured by trypan blue, and fluorescence staining methods. The expression level of interleukin-8 (IL-8) cytokine-encoding genes was also investigated by a qRT-PCR assay in all pathogens and co-cultured groups in HT-29 cells. Our results showed that 4% B. coagulans CFS reduced pathogen growth. The highest rate of growth inhibition was observed in L. monocytogenes. We also found that B. coagulans, and its 4% CFS reduced the cytotoxic effects of pathogens, with the exception of S. aureus. Non-pathogenic E. coli also had no significant cytotoxic effect on the cells. Examination of the treated cells with acridine orange/ethidium bromide staining showed reductions in the rate of cell damage (including early apoptosis, late apoptosis, and necrosis) in pathogen-probiotic co-cultures. Furthermore, we showed that co-culture of pathogens with B. coagulans significantly down-regulated IL-8 gene expression (P < 0.05). The greatest down-regulation compared with pathogen alone was observed in S. aureus. Hence, B. coagulans can be considered as an appropriate probiotic to diminish cytotoxicity, and inflammatory response of enteropathogenic bacteria.

Probiotic Bacillus subtilis CW14 reduces disruption of the epithelial barrier and toxicity of ochratoxin A to Caco-2 cells

The multiple toxic effects of ochratoxin A (OTA) are a threat for human and animal. This study aimed to examine whether B. subtilis CW14 protected against OTA-induced barrier disruption and cell damage to Caco-2 cells. The results showed that Caco-2 cells treated with OTA led to microvilli disruption, tight junction protein (ZO-1 and claudin-1) damage, and inhibition of cell proliferation by arresting the cell cycle in the G2/M phase that promoted apoptosis. The treatment of B. subtilis CW14 mitigated the tight junction injury by improving ZO-1 protein expression, and it reduced apoptosis that was induced by OTA. Furthermore, transcriptome analysis indicated that OTA down-regulated genes that involved in the tight junction, cell cycle, and apoptosis-related signaling pathways. B. subtilis CW14 may have protected the ZO-1 protein by activating the toll-like receptor signaling pathway, and it reduced OTA damage by down-regulating the death receptor genes and up-regulating the DNA repair genes. These findings demonstrated the importance of B. subtilis CW14 in the regulation of tight junction proteins and in reducing death of intestinal epithelial cells. Thus, B. subtilis CW14 is a potential candidate as a food additive to protect against intestinal damage.

Bacillus probiotics: an alternative to antibiotics for livestock production

The use of probiotics as feed supplements in animal production has increased considerably over the last decade, particularly since the ban on antibiotic growth promoters in the livestock sector. Several Bacillus sp. are attractive for use as probiotic supplements in animal feed due to their ability to produce spores. Their heat stability and ability to survive the low pH of the gastric barrier represent an advantage over other probiotic micro-organisms. This review discusses important characteristics required for selection of Bacillus probiotic strains and summarizes the beneficial effect of Bacillus-based feed additives on animal production. Although the mechanism of action of Bacillus probiotics has not been fully elucidated, they are effective in improving the growth, survival and health status of terrestrial and aquatic livestock. Bacillus strains also have utility in bioremediation and can reduce nitrogenous waste, thereby improving environmental conditions and water quality. Finally, recent innovative approaches for using Bacillus spores in various applications are discussed.

The effects of probiotic Bacillus subtilis on the cytotoxicity of Clostridium perfringens type a in Caco-2 cell culture

Background

Some Bacillus strains have recently been identified for potential use as probiotics and food additives. The present study evaluated the antimicrobial effects of Bacillus subtilis ATCC 6633 and its metabolite on the enterotoxin and vegetative cells, spore and germinated spore of Clostridium perfringens type A in Caco-2 cells.

Results

We used flow cytometry and MTT assays to evaluate the cytotoxicity effect of treatments. According to the results, the most cell survival was found in the 4% crude antimicrobial substance (CAS) with the vegetative form of C. perfringens among co-cultured groups. Furthermore, the apoptosis and necrosis in co-cultured groups were significantly decreased (P < 0.05).

Conclusion

The present results suggested the crucial role of the current probiotic in the control of various forms of C. perfringens type A which was investigated for the first time. Also, the majority of treatments showed higher cell viability in flow cytometry compared to the MTT assay.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-1051-1) contains supplementary material, which is available to authorized users.

Bacillus subtilis and surfactin inhibit the transmissible gastroenteritis virus from entering the intestinal epithelial cells

Intestinal epithelial cells are the targets for transmissible gastroenteritis (TGE) virus (TGEV) infection. It is urgent to develop a novel candidate against TGEV entry. Bacillus subtilis is a probiotic with excellent anti-microorganism properties and one of its secretions, surfactin, has been regarded as a versatile weapon for most plant pathogens, especially for the enveloped virus. We demonstrate for the first time that B. subtilis OKB105 and its surfactin can effectively inhibit one animal coronavirus, TGEV, entering the intestinal porcine epithelial cell line (IPEC-J2). Then, several different experiments were performed to seek the might mechanisms. The plaque assays showed that surfactant could reduce the plaque generation of TGEV in a dose-dependent manner. Meanwhile, after incubation with TGEV for 1.5 h, B. subtilis could attach TGEV particles to their surface so that the number of virus to bind to the host cells was declined. Furthermore, our data showed that the inhibition of B. subtilis was closely related to the competition with TGEV for the viral entry receptors, including epidermal growth factor receptor (EGFR) and aminopeptidase N (APN) protein. In addition, Western blotting and apoptosis analysis indicated that B. subtilis could enhance the resistance of IPEC-J2 cells by up-regulating the expression of toll-like receptor (TLR)-6 and reducing the percentage of apoptotic cells. Taken together, our results suggest that B. subtilis OKB105 and its surfactin can antagonize TGEV entry in vitro and may serve as promising new candidates for TGEV prevention.

Biosurfactins production by Bacillus amyloliquefaciens R3 and their antibacterial activity against multi-drug resistant pathogenic E. coli

In this work, the anti-Escherichia coli activity of the bioactive substances produced by Bacillus amyloliquefaciens R3 was examined. A new and cheap medium for production of the anti-E. coli substances which contained 20.0 g L(-1) soybean powder, 20.0 g L(-1) wheat flour, pH 6.0 was developed. A crude surfactant concentration of 0.48 mg mL(-1) was obtained after 27 h of 10-L fermentation, and the diameter of the clear zone on the plate seeded with the pathogenic E. coli 2# was 23.3 mm. A preliminary characterization suggested that the anti-E. coli substances produced by B. amyloliquefaciens R3 were the biosurfactins (F1, F2, F3, F4, and F5) with amino acids (GLLVDLL) and hydroxy fatty acids (of 12-15 carbons in length). It was found that all the strains of the pathogenic E. coli showed resistance to several different antibiotics, suggesting that they were the multi-drug resistance and all the strains of the pathogenic E. coli were sensitive to the biosurfactins, indicating that the biosurfactins produced by B. amyloliquefaciens R3 had a broad spectrum of antibacterial activity against the pathogenic E. coli with multi-drug resistant profiles. After the treatment with the purified biosurfactin (F1), the cell membrane of both the whole cells and protoplasts of the E. coli 2# was damaged and the whole cells of the bacterium were broken.