A novel multifunctional peptide oligomer of bacitracin with possible bioindustrial and therapeutic applications from a Korean food-source Bacillus strain

A novel antimicrobial peptide YS12 isolated from Bacillus velezensis CBSYS12 exerts anti-biofilm properties against drug-resistant bacteria

Nowadays, the abuse of antibiotics has led to the rise of multi-drug-resistant bacteria. Antimicrobial peptides (AMPs), with broad-spectrum antimicrobial activity have attracted considerable attention as possible alternatives to traditional antibiotics. In this work, we aimed to evaluate the antimicrobial and anti-biofilm activity of an antimicrobial peptide designed as YS12 derived from Bacillus velezensis CBSYS12. The strain CBSYS12 was isolated from Korean food kimchi and purified followed by ultrafiltration and sequential chromatographic methodology. Hereafter, Tricine SDS-PAGE revealed a single protein band of around 3.3 kDa that was further confirmed in situ inhibitory activity of the gel. A similar molecular weight (~ 3348.4 Da) protein also appeared in MALDI-TOF confirming the purity and homogeneity of peptide YS12. Intriguingly, YS12 revealed a strong antimicrobial activity with a minimum inhibitory concentration (MIC) value ranging from 6 to 12 μg/ml for both Gram-positive and Gram-negative bacteria, such as E. coli, P. aeruginosa, MRSA 4-5, VRE 82, and M. smegmatis. We also determined the mode of action of the peptide against pathogenic microorganisms using different fluorescent dyes. In addition, the anti-biofilm assay demonstrated that peptide YS12 was able to inhibit biofilm formation  around 80% for both bacterial strains E. coli and P. aeruginosa at 80 µg/ml. Notably, YS12 exhibited a greater biofilm eradication activity than commercial antibiotics. In summary, our study proposed that peptide YS12 may be used as a promising therapeutic agent to overcome drug and biofilm-related infections.

Protective effects of Bacillus licheniformis on growth performance, gut barrier functions, immunity and serum metabolome in lipopolysaccharide-challenged weaned piglets

Bacillus licheniformis (B. licheniformis) is a well-accepted probiotic that has many benefits on both humans and animals. This study explored the effects of B. licheniformis on growth performance, intestinal mucosal barrier functions, immunity as well as serum metabolome in the weaned piglets exposed to lipopolysaccharide (LPS). One hundred and twenty piglets weaned at four weeks of age were separated into two groups that received a basal diet (the control group, CON), and a basal diet complemented with B. licheniformis (500 mg/kg, the BL group, BL). Twenty-four piglets were chosen from the above two groups and 12 piglets were injected with LPS intraperitoneally at a concentration of 100 μg/kg and the others were injected with sterile saline solution of the same volume. All the piglets were sacrificed 4 h after LPS challenge. Results showed that B. licheniformis enhanced the ADG and final body weight and lowered the F/G and diarrhea rate. Pre-treatment with B. licheniformis markedly attenuated intestinal mucosal damage induced by LPS challenge. Supplementation with B. licheniformis strengthened immune function and suppressed inflammatory response by elevating the concentrations of serum immunoglobulin (Ig) A and jejunum mucosal IgA and IgG and decreasing serum IL-6 and jejunum mucosal IL-1β. In addition, B. licheniformis pretreatment prevented LPS-induced intestinal injury by regulating the NLRP3 inflammasome. Furthermore, pretreatment with B. licheniformis tended to reverse the reduction of acetate and propionic acids in the colonic contents that occurred due to LPS stress. B. licheniformis markedly modulated the metabolites of saccharopine and allantoin from lysine and purine metabolic pathways, respectively. Overall, these data emphasize the potentiality of B. licheniformis as a dietary supplement to overcome the challenge of bacterial LPS in the animal and to enhance the food safety.

Reduction of Oxidative Stress through Activating the Nrf2 mediated HO-1 Antioxidant Efficacy Signaling Pathway by MS15, an Antimicrobial Peptide from Bacillus velezensis

The efficient culture and purification of antimicrobial peptides (AMPs), along with intense antioxidant activity, have drawn the interest to study antioxidant activity mechanism. We report the culture conditions optimization, efficient biosynthesis, and purification of an antioxidant peptide MS15 from Bacillus velezensis obtained from fermented food that would generate heme oxygenase-1 (HO-1) expression and lead to nuclear factor erythroid 2-related factor-2 (Nrf2) nuclear translocation. We explored the ability of kinetics and potency for the bacterial killing to work against various pathogenic bacteria. A bioassay showed the lysis zone of MS15 by tricine SDS-PAGE near at 6 kDa. MALDI-TOF/MS verified molecular weight, and the existence of a molecular mass of 6091 Da was reported by purity. The MIC of MS15 ranged from 2.5-160 μg/mL for many pathogenic bacteria, showing greater potency. In macrophage RAW 264.7 cells, MS15 was exposed to assess its inhibitory effect against the generation of reactive oxygen species (ROS) in oxidative stress. In the sample treated group, the translation, and transcriptional levels of CAT (catalase), GPx (glutathione peroxidase), and SOD (superoxide dismutase) were significantly greater. In short, MS15 has significant antioxidant properties, reducing ROS production in RAW 264.7 cells, and raising the translation and transcriptional rates of antioxidant enzymes with stimulating HO-1 induction facilitated by Nrf2.

Regulatory Effect of Lactobacillus brevis Bmb6 on Gut Barrier Functions in Experimental Colitis

The integrity of gut barrier functions is closely associated with the pathogenesis of colitis. It is speculated that Lactobacillus brevis Bmb6 alleviates colitis by improving the tight junction (TJ) of the inflamed intestinal epithelial layer. In the present study, the regulatory effects of L. brevis Bmb6 on the TJ barrier to ameliorate colitis-symptoms were investigated. Preliminary screening showed that L. brevis Bmb6 exhibited strong acid and bile acid tolerance, along with antioxidants and β-galactosidase activities. In a 14-day dextran sulfate sodium (DSS)-induced colitis mouse model, treatment with L. brevis Bmb6 significantly decreased in the disease activity index score. In addition, histological analyses showed that treatment with L. brevis Bmb6 protected the structural integrity of the intestinal epithelial layer and mucin-secreting goblet cells from DSS-induced damage, with only slight infiltration of immune cells. Interestingly, western blotting analyses showed that the expression of the TJ protein, zona occluden-1, was restored in Bmb6-treated mice, but not in DSS-induced mice. Consistently, the gene expression of inflammatory cytokines (tumor necrosis factor-α and interferon-γ) was also suppressed in the Bmb6-treated mice. Hence, our findings suggest that suppression of inflammatory conditions enhanced expression of TJ protein, ZO-1, or vice versa, contributing to a colitis-ameliorating effect in L. brevis Bmb6.

Response Surface Optimization of Culture Conditions for Cyclic Lipopeptide MS07 from Bacillus siamensis Reveals Diverse Insights Targeting Antimicrobial and Antibiofilm Activity

Efforts to isolate a broad-spectrum antimicrobial peptide (AMP) from microbial sources have been on the rise recently. Here, we report the identification, the optimization of the culture conditions, and the characterization of an efficient AMP from the Bacillus strain designated MS07 that exhibits antimicrobial and antibiofilm activity. The production of MS07 was maximized by evaluating the culture conditions by the response surface methodology to obtain optimum media compositions. The biochemical integrity of MS07 was assessed by a bioassay indicating inhibition at ~6 kDa, like tricine-SDS-PAGE. MALDI-TOF confirmed the molecular weight and purity, showing a molecular mass of 6.099 kDa. Peptide MS07 exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria. The MIC of MS07 for Escherichia coli, Alcaligenes faecalis, MRSA, and Pseudomonas aeruginosa ranged from 16–32 µg/mL, demonstrating superior potency. The biomass was diminished by about 15% and 11%, with rising concentrations up to 8 × MIC, for P. aeruginosa and E. coli biofilm, respectively. MS07 exhibited an 8 µM and 6 µM minimum bactericidal concentration against the biofilm of the Gram-negative strains P. aeruginosa and E. coli, respectively. Peptide MS07 reduced and interrupted the biofilm development in a concentration-dependent manner, as determined by BacLight live/dead staining using confocal microscopy.

A Novel Peptide Oligomer of Bacitracin Induces M1 Macrophage Polarization by Facilitating Ca2+ Influx

Antimicrobial peptides (AMPs) are components of the innate immune system and form the first defense against pathogens for various organisms. In the present study, we assessed whether CSP32, a novel AMP oligomer of bacitracin isolated from a strain of Bacillus spp., regulates the polarization of murine macrophage-like RAW 264.7 cells. CSP32 stimulated phagocytosis while inducing the appearance of the typical M1 polarized macrophage phenotype; these M1 macrophages play a role in host defense against pathogens. Furthermore, our results showed that CSP32 enhanced the expression and production of pro-inflammatory mediators, such as cytokines and chemokines. In addition, the CSP32-stimulated inflammatory mediators were induced mainly by the mitogen-activated protein kinase/nuclear factor kappa B (MAPK/NF-κB) signaling pathway during M1 macrophage polarization. In particular, CSP32 markedly increased the numbers of Ca²⁺-positive macrophages while upregulating phospholipase C and activating protein kinase Cε. Furthermore, the inhibition of intracellular Ca²⁺ by BAPTA-AM, a Ca²⁺ chelator, significantly suppressed the CSP32-mediated phagocytosis, inflammatory mediator production, and NF-κB activation. In conclusion, our data suggested that CSP32-stimulated M1 macrophage polarization is dependent on the calcium signaling pathway and may result in enhanced immune capacities.

Identification and characterization of antimicrobial peptide produced by indigenously isolated Bacillus paralicheniformis UBBLi30 strain

The antimicrobial compound produced by Bacillus paralicheniformis UBBLi30 showed UV spectra absorption at 208 nm. Fourier transform infrared (FTIR) revealed characteristic bands for aliphatic chain related to hydrophobic amino acids (l-isoleucine/l-leucine) (3068, 2965 and 2871 cm^-1) and peptide bonds (1538, 1667 and 3312 cm^-1). The proton nuclear magnetic resonance (¹H NMR) showed signals for aromatic amino acid (6.5-9.5 ppm) and alkyl amines (3-4 ppm). The results of carbon (¹³C) NMR showed signals for aromatic, nitro and amide compounds. Besides this, the mass fragments (1422.576 [M+H]⁺, 711.912 [M+2H]²⁺ and 475.174 [M+3H]³⁺ m/z) observed in electrospray ionization mass spectrometry (ESI-MS) were coordinated well to the fragments of polypeptide antibiotic bacitracin. The presence of bacA gene further confirmed the production of bacitracin. Bacitracin inhibited the growth of a range of Gram-positive bacteria such as Micrococcus luteus, methicillin-resistant Staphylococcus aureus (MRSA), S. aureus, Streptococcus pyogenes and Propionibacterium acnes, and biofilm formation of M. luteus and MRSA. Moreover, this polypeptide reduced the zeta potential of M. luteus and MRSA, indicating the electrostatic sorption on bacterial surface and concentration-dependent cell membrane damages. Besides this, polypeptide showed stability in the presence of proteases (proteinase K, trypsin and pepsin), pH (1, 3, 5, 7, 9 and 11) and temperature up to 100 °C. B. paralicheniformis UBBLi30 therefore has the potential to be utilized as a bio-preservative to control the growth of spoilage and pathogenic bacteria.

A novel antioxidant peptide, purified from Bacillus amyloliquefaciens, showed strong antioxidant potential via Nrf-2 mediated heme oxygenase-1 expression

A novel antioxidant peptide YD1 (∼1.0kDa), purified from the strain Bacillus amyloliquefaciens CBSYD1, displayed activity in several in vitro assays and was also efficient against Gram-positive, Gram-negative as well as multidrug-resistant (MDR) bacteria. Strain growth was adapted to bile-salt conditions where a clear halos-zone was observed in a bile-salt plate assay and was viable in different digestive track conditions. YD1 treatment on RAW 264.7 cells increased the transcriptional and translational activities of NF-E2-related factor-2 (Nrf-2) through the enhanced levels of heme oxygenase-1 (HO-1). Furthermore, the YD1-treated group showed higher levels of antioxidant enzymes compared to the oxidative stress group. YD1 demonstrated a strong antioxidant activity by decreasing nitric oxide (NO) and reactive oxygen species (ROS) in RAW 264.7 cells. This study suggests that YD1 and the strain could be a natural antioxidant and a probiotic candidate respectively.