A novel thermotolerant and acidotolerant peptide produced by a Bacillus strain newly isolated from a fermented food (kimchi) shows activity against multidrug-resistant bacteria

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.

Antimicrobial Peptides with Antibacterial Activity against Vancomycin-Resistant Staphylococcus aureus Strains: Classification, Structures, and Mechanisms of Action

The emergence of bacteria resistant to conventional antibiotics is of great concern in modern medicine because it renders ineffectiveness of the current empirical antibiotic therapies. Infections caused by vancomycin-resistant Staphylococcus aureus (VRSA) and vancomycin-intermediate S. aureus (VISA) strains represent a serious threat to global health due to their considerable morbidity and mortality rates. Therefore, there is an urgent need of research and development of new antimicrobial alternatives against these bacteria. In this context, the use of antimicrobial peptides (AMPs) is considered a promising alternative therapeutic strategy to control resistant strains. Therefore, a wide number of natural, artificial, and synthetic AMPs have been evaluated against VRSA and VISA strains, with great potential for clinical application. In this regard, we aimed to present a comprehensive and systematic review of research findings on AMPs that have shown antibacterial activity against vancomycin-resistant and vancomycin-intermediate resistant strains and clinical isolates of S. aureus, discussing their classification and origin, physicochemical and structural characteristics, and possible action mechanisms. This is the first review that includes all peptides that have shown antibacterial activity against VRSA and VISA strains exclusively.

Functional Annotation Genome Unravels Potential Probiotic Bacillus velezensis Strain KMU01 from Traditional Korean Fermented Kimchi

Bacillus velezensis strain KMU01 showing γ-glutamyltransferase activity as a probiotic candidate was isolated from kimchi. However, the genetic information on strain KMU01 was not clear. Therefore, the current investigation was undertaken to prove the probiotic traits of B. velezensis strain KMU01 through genomic analysis. Genomic analysis revealed that strain KMU01 did not encode enterotoxin genes and acquired antibiotic resistance genes. Strain KMU01 genome possessed survivability traits under extreme conditions such as in the presence of gastric acid, as well as several probiotic traits such as intestinal epithelium adhesion and the production of thiamine and essential amino acids. Potential genes for human health enhancement such as those for γ-glutamyltransferase, nattokinase, and bacteriocin production were also identified in the genome. As a starter candidate for food fermentation, the genome of KMU01 encoded for protease, amylase, and lipase genes. The complete genomic sequence of KMU01 will contribute to our understanding of the genetic basis of probiotic properties and allow for the assessment of the effectiveness of this strain as a starter or probiotic for use in the food industry.

Purification, characterization, and chemical modification of Bacillus velezensis SN-14 fibrinolytic enzyme

Fermented bean foods are a crucial source of fibrinolytic enzymes. The presented study aimed to purify, characterize, and chemically modify Bacillus velezensis SN-14 fibrinolytic enzyme. The fibrinolytic enzyme was purified using CTAB/isooctane/hexyl alcohol/n-butyl alcohol reverse micellar system, and the purified enzyme was chemically modified to improve its enzymatic activity and stability. Enzyme activity recovery and the purification fold for this enzyme were 44.5 ± 1.9% and 4.93 ± 0.05 fold, respectively. SDS-PAGE results showed that the molecular weight of the purified fibrinolytic enzyme was around 28 kDa. Besides, the optimum temperature and pH of the purified fibrinolytic enzyme were 37 °C and 8-9, respectively. Fe²⁺, mPEG5000, and pepsin were used for chemical modification and for improving the activity and stability of the purified enzyme. Thermal and acid-base stability of chemically modified enzymes increased significantly, whereas enzymatic activity increased by 7.3 times. After 30 d of frozen storage, the modified enzyme's activity was remarkably lower (33.2%) than the unmodified enzyme (60.6%). The current study on B. velezensis SN-14 fibrinolytic enzyme and chemical modification method using Fe²⁺, mPEG5000, and pepsin provide a reference for developing fibrinolytic drugs and foods.

Purification and partial characterization of a low molecular fibrinolytic serine metalloprotease C142 from the culture supernatant of Bacillus subtilis C142

Novel serine metalloprotease-like enzyme, C142 was purified from the culture supernatant of Bacillus subtilis C142. The C142 was purified to homogeneity by a two-step procedure with a 20.7-fold increase in specific activity and 0.9% recovery. The molecular mass of C142 was approximately 23.5kDa based on SDS-PAGE. The N-terminal amino acid sequence of the first 21 amino acids of C142 was AQSVPYGISQIKAPALHSQGY. Its optimum pH, optimum temperature, pH stability, and thermal stability were pH 6, 40°C, pH 6-8, and 20-35°C, respectively. C142 was strongly inhibited by PMSF and EGTA, suggesting that C142 was a serine metalloprotease-like enzyme. C142 showed the highest specificity toward the substrate for t-PA. The apparent K_m, V_max, and K_cat values of C142 toward H-d-Ile-Pro-Arg-pNA were determined as 0.34mM, 0.25mmolmg^-1min^-1, and 46.83s^-1. C142 exhibited fibrinolytic activity, which is stronger than that of plasmin. C142 hydrolyzed Aα, and Bβ-chains of fibrinogen, but did not cleave γ-chains. C142 had antithrombotic effect in three animal models. C142 was devoid of hemorrhagic activity at a dose of 20,000FU/kg. Taken together, our results indicate that B. subtilis C142 produces a serine metalloprotease-like enzyme/fibrinolytic enzyme and this enzyme might be used as a new thrombolytic agent.

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

Investigating the effects of a multifunctional microbial peptide possessing strong anti-inflammatory activity against pathogenic bacteria. The antimicrobial activity of the purified peptide (CSP32) against various multidrug-resistant as well as anaerobic pathogens was determined. Anti-inflammatory activity was determined by an enzyme-linked immunosorbent assay, western blotting, and RT-PCR in RAW 264.7 macrophages. Molecular weight and structural elucidation were performed by several analytical methods such as mass spectrometry and chemoinformatic analysis. CSP32, purified from newly isolated Bacillus sp. CS32, was active against methicillin-resistant Staphylococcus aureus, vancomycin-resistant S. aureus, vancomycin-resistant enterococci, and anaerobic pathogens Propionibacterium acne and Clostridium difficile. Furthermore, CSP32 showed strong inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production and nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) expression in RAW 264.7 macrophages. At concentrations of 10, 50, and 100 μg/mL, CSP32 treatment attenuated LPS-induced expression of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) as well as other proinflammatory mediators such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and IL-1β. CSP32 potently inhibited translocation of NF-κB into the nucleus by suppressing degradation of IκB kinase (IκBα) and its phosphorylation, thereby causing NF-κB to remain inactive. CSP32 may be the first oligomer of bacitracin with anti-inflammatory properties.

A multifunctional alanine-rich anti-inflammatory peptide BCP61 showed potent inhibitory effects by inhibiting both NF-κB and MAPK expression

The purified BCP61 was reported to be a unique low-molecular-weight (MW) anti-microbial peptide because of its non-identical alanine-rich N-terminal sequence. In this study, we investigated the anti-inflammatory effects of BCP61 on induction of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), pro-inflammatory cytokines, nuclear factor-kappa B (NF-κB), and mitogen-activated protein kinases (MAPKs) in lipopolysaccharide (LPS)-stimulated Raw 264.7 cells. The treatment with BCP61, with varying concentrations of 10, 50, and 100 μg/mL, inhibited levels of expression of LPS-induced NF-κB and MAPKs (extracellular signal-related kinases (ERKs), c-Jun NH₂-terminal kinase (JNK), and mitogen-activated protein (p38)) as well as production of pro-inflammatory mediators, such as nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). The results suggested that BCP61 prevents inhibitor of kappa B (IκBα) phosphorylation and degradation, thereby inhibiting the nuclear translocation of the p65 protein. We do report that the use of BCP61 in the treatment of inflammation as well as microbial infection could be a potent therapeutic candidate.

Antimicrobial peptide isolated from Bacillus amyloliquefaciens K14 revitalizes its use in combinatorial drug therapy

The present study was performed to evaluate the antibacterial activities of an antimicrobial peptide (CSpK14) and the synergies thereof with β-lactams against vancomycin-resistant Staphylococcus aureus (VRSA) and Enterococci (VRE). Our strain was isolated from fermented food (kimchi), which is 99.79 % homologous with Bacillus amyloliquefaciens subsp. plantarum FZB42(T). CSpK14 was purified to homogeneity by diammonium sulfate precipitation, concentration, dialysis, and followed by two-stage chromatographic separation, i.e., Sepharose Cl-6B and Sephadex G-25 chromatography, and had a molar mass of ~4.6 kDa via Tricine SDS-PAGE and in situ examination. It was stable at pH 6.0-11.5 and temperature up to 80 °C. In addition, it was also stable with various metal ions, solvents, and proteases. The N-terminal amino acid sequence was H-Y-D-P-G-D-D-S-G-N-T-G and did not show any significant homology with reported peptides. However, it shows some degrees of identity with alpha-2-macroglobulin and ligand-gated channel protein from different microorganisms. CSpK14 significantly reduced the minimum inhibitory concentrations (MICs) of β-lactams and had no effect on non-β-lactams against VRSA and VRE. MICs of CSpK14/oxacillin and CSpK14/ampicillin were reduced by 8- to 64-fold and 2- to 16-fold, respectively. The time killing assay between CSpK14/oxacillin (2.29-2.37 Δlog₁₀CFU/mL at 24 h) and CSpK14/ampicillin (2.30-2.38 Δlog₁₀CFU/mL at 24 h) being >2-fold and fractional inhibitory concentration index ˂0.5 revealed synergy. Furthermore, the biofilms formed by VRSA and VRE were reduced completely. CSpK14 was simple to purify, had low molecular mass, was stable over a wide pH range or tested chemicals, had broad inhibitory spectrum, and possessed potent synergistic antimicrobial-antibiofilm properties. CSpK14 synergistically enhanced the efficacy of β-lactams and is therefore suitable for combination therapy.