Biomedical applications of nisin

The antimicrobial peptide nisin Z induces selective toxicity and apoptotic cell death in cultured melanoma cells

Reprogramming of cellular metabolism is now considered one of the hallmarks of cancer. Most malignant cells present with altered energy metabolism which is associated with elevated reactive oxygen species (ROS) generation. This is also evident for melanoma, the leading cause of skin cancer related deaths. Altered mechanisms affecting mitochondrial bioenergetics pose attractive targets for novel anticancer therapies. Antimicrobial peptides have been shown to exhibit selective anticancer activities. In this study, the anti-melanoma potential of the antimicrobial peptide, nisin Z, was evaluated in vitro. Nisin Z was shown to induce selective toxicity in melanoma cells compared to non-malignant keratinocytes. Furthermore, nisin Z was shown to negatively affect the energy metabolism (glycolysis and mitochondrial respiration) of melanoma cells, increase reactive oxygen species generation and cause apoptosis. Results also indicate that nisin Z can decrease the invasion and proliferation of melanoma cells demonstrating its potential use against metastasis associated with melanoma. As nisin Z seems to place a considerable extra burden on the energy metabolism of melanoma cells, combination therapies with known anti-melanoma agents may be effective treatment options.

Acid or erythromycin stress significantly improves transformation efficiency through regulating expression of DNA binding proteins in Lactococcus lactis F44

Lactococcus lactis is a gram-positive bacterium used extensively in the dairy industry and food fermentation, and its biological characteristics are usually improved through genetic manipulation. However, poor transformation efficiency was the main restriction factor for the construction of engineered strains. In this study, the transformation efficiency of L. lactis F44 showed a 56.1-fold increase in acid condition (pH 5.0); meanwhile, erythromycin stress (0.04 μg/mL) promoted the transformation efficiency more significantly (76.9-fold). Notably, the transformation efficiency of F44e (L. lactis F44 harboring empty pLEB124) increased up to 149.1-fold under the synergistic stresses of acid and erythromycin. In addition, the gene expression of some DNA binding proteins (DprA, RadA, RadC, RecA, RecQ, and SsbA) changed correspondingly. Especially for radA, 25.1-fold improvement was detected when F44e was exposed to pH 5.0. Overexpression of some DNA binding proteins could improve the transformation efficiency. The results suggested that acid or erythromycin stress could improve the transformation efficiency of L. lactis through regulating gene expression of DNA binding proteins. We have proposed a simple but promising strategy for improving the transformation efficiency of L. lactis and other hard-transformed microorganisms.

The physiological response of broiler chickens to the dietary supplementation of the bacteriocin nisin and ionophore coccidiostats

The aim of this study was to investigate the effect of dietary supplementation with nisin alone or in combination with salinomycin or monensin on broiler chickens in terms of growth performance, selected blood parameters, digestive enzyme activity, apparent nutrient digestibility, and tibiotarsus mineralization, as well as selected gastrointestinal tract (GIT) organ weights, intestinal length, and central immune organ weights. Two independent experiments, each including 400 one-day-old female Ross 308 chicks differing in ionophore coccidiostats, i.e., salinomycin and monensin supplementation, were conducted. The following treatments were applied: experiment 1: NA-no additives, SAL-salinomycin (60 mg/kg diet), NIS-nisin (2,700 IU/kg diet), SAL+NIS-salinomycin (60 mg/kg diet) and nisin (2,700 IU/kg diet); experiment 2: NA-no additives, MON-monensin (100 mg/kg diet), NIS-nisin (2,700 IU/kg diet) and MON+NIS-monensin (100 mg/kg diet) and nisin (2,700 IU/kg diet). The addition of nisin with or without ionophores to the birds' diet improved broiler growth performance in terms of BWG and FCR (days 1 to 14) and BWG and FI (15 to 35 d; 1 to 35 d). Salinomycin showed effects similar to those of nisin influence on growth performance (1 to 35 d), while monensin supplementation resulted in lower BWG. Moreover, no additive effect between nisin and ionophores was observed. Nisin and salinomycin had no influence on the serum concentration of selected hormones and other blood biochemical parameters except glucose, which was reduced by nisin. A decrease in lipase activity was observed during nisin and salinomycin supplementation, while the apparent ileal digestibility of fat was not affected. However, the digestibility of crude protein increased with nisin administration. Additionally, the effects of nisin on decreasing the weight and length of GIT segments were observed. Supplementation with nisin and monensin was not associated with a negative impact on tibiotarsus mineralization and the immune organ index. This study suggests that nisin may be used in broiler nutrition as a growth promotor, with no negative influence on the bird's metabolism or immune status.

Discovery of a novel lantibiotic nisin O from Blautia obeum A2-162, isolated from the human gastrointestinal tract

A novel lanC-like sequence was identified from the dominant human gut bacterium Blautia obeum strain A2-162. This sequence was extended to reveal a putative lantibiotic operon with biosynthetic and transport genes, two sets of regulatory genes, immunity genes, three identical copies of a nisin-like lanA gene with an unusual leader peptide, and a fourth putative lanA gene. Comparison with other nisin clusters showed that the closest relationship was to nisin U. B. obeum A2-162 demonstrated antimicrobial activity against Clostridium perfringens when grown on solid medium in the presence of trypsin. Fusions of predicted nsoA structural sequences with the nisin A leader were expressed in Lactococcus lactis containing the nisin A operon without nisA. Expression of the nisA leader sequence fused to the predicted structural nsoA1 produced a growth defect in L. lactis that was dependent upon the presence of biosynthetic genes, but failed to produce antimicrobial activity. Insertion of the nso cluster into L. lactis MG1614 gave an increased immunity to nisin A, but this was not replicated by the expression of nsoI. Nisin A induction of L. lactis containing the nso cluster and nisRK genes allowed detection of the NsoA1 pre-peptide by Western hybridization. When this heterologous producer was grown with nisin induction on solid medium, antimicrobial activity was demonstrated in the presence of trypsin against C. perfringens, Clostridium difficile and L. lactis. This research adds to evidence that lantibiotic production may be an important trait of gut bacteria and could lead to the development of novel treatments for intestinal diseases.

Functions and emerging applications of bacteriocins

Bacteriocins, defined as ribosomally synthesized antimicrobial peptides, have traditionally been used as food preservatives, either added or produced by starter cultures during fermentation. In-depth studies of a select few bacteriocins opened exiting new research fields and broadened the application of these antimicrobial peptides. The possibility of developing bacteriocins into next generation antibiotics, accompanied with the rapid development in genetics and nanotechnology, paves the way to even more fascinating applications such as novel carrier molecules (delivery systems) and the treatment of cancer. Also, some bacteriocins are found to regulate quorum sensing which suggests novel applications for this group of substances. While there is some interesting translational research on bacteriocins from Gram-negative bacteria, the majority of application-oriented studies are focused on bacteriocins from Gram-positive microorganisms, mostly lactic acid bacteria. The applications of bacteriocins are expanding from food to human health.

Improving xylose utilization of defatted rice bran for nisin production by overexpression of a xylose transcriptional regulator in Lactococcus lactis

Present investigation explores the potential of defatted rice bran (DRB) serving as sole carbon source and partial nitrogen source to support Lactococcus lactis growth and nisin production. To retain the nutrients in DRB, especially protein fractions, thermal pretreatment followed by enzymatic hydrolysis without washing step was applied for saccharification. A maximum of 45.64g reducing sugar mainly containing 30.26g glucose and 5.66g xylose from 100g DRB was attained in hydrolysates of DRB (HD). A novel strategy of xylR (xylose transcriptional regulator) overexpression followed by evolutionary engineering was proposed, which significantly increased the capacity of L. lactis to metabolize xylose. Subsequently, RT-PCR results indicated that xylR overexpression stimulated expression of xylose assimilation genes synergistically with exposure to xylose. In HD medium, the highest nisin titer of the engineered strain FEXR was 3824.53IU/mL, which was 1.37 times of that in sucrose medium by the original strain F44.

Efficient production and optimization of E7 oncoprotein from Iranian human papillomavirus type 16 in Lactococcus lactis using nisin-controlled gene expression (NICE) system

The present work was aimed at investigating the expression and optimization of a human papillomavirus (HPV) type 16 gene encoding oncoprotein E7 in Lactococcus lactis. We genetically engineered Lactococcus lactis using nisin-controlled gene expression (NICE) system pNZ8148 to express the native and codon optimized E7 oncogenes isolated from Iranian HPV-16. The results of optimizing fermentation showed, the concentration of produced protein was expressively improved by 10 ng/mL nisin after 3.5, and 4 h induction for NZ9000 harboring the codon-optimized, and native E7 respectively. Furthermore the recombinant NZ9000 strains expressed rE7 by maximum value of 4.7 (Codon-optimized), and 1.82 μg/mL (Native) in static flask experiments at initial glucose concentrations of 50 and 75 g/L respectively. The rE7 yield was further enriched in batch fermenter experiments using controlled pH. Thus, the overall production of rE7 under optimized conditions accumulated in the cytoplasm to nearly 33.25 μg/mL by L. lactis NZ9000 containing codon-optimized E7, which was over ∼2.7-fold higher compared to the NZ9000 having native E7 strain (12.01 μg/mL). Accordingly, the maximum biomass production was calculated 4.87, and 1.51 g/L respectively.

Improving nitrogen source utilization from defatted soybean meal for nisin production by enhancing proteolytic function of Lactococcus lactis F44

Nisin, one kind of natural antimicrobial peptide, is produced by certain Lactococcus lactis strains, which generally require expensive high-quality nitrogen sources due to limited ability of amino acids biosynthesis. Here we use defatted soybean meal (DSM) as sole nitrogen source to support L. lactis growth and nisin production. DSM medium composition and fermentation conditions were optimized using the methods of Plackett-Burman design and central composite design. The highest nisin production of 3879.58 IU/ml was obtained in DSM medium, which was 21.3% higher than that of commercial medium. To further increase the utilization ability of nitrogen sources, we enhanced the proteolytic function in L. lactis through rationally expressing the related enzymes, which were selected according to the compositions of amino acids and molecular weight of peptides in DSM medium. Significantly, an artificial proteolytic system consisting of a heterologous protease (NprB), an oligopeptides transporter subunit (OppA) and two peptidases (PepF and PepM) was introduced into L.lactis. The constructed strain BAFM was capable of achieving efficient biomass accumulation and nisin yield with 30% decreased amount of DSM hydrolysates, which further reduced the cost of nisin production. The strategy described here offers opportunities for low-cost L. lactis fermentation and large-scale nisin production in industry.

Promoting acid resistance and nisin yield of Lactococcus lactis F44 by genetically increasing D-Asp amidation level inside cell wall

Nisin fermentation by Lactococcus lactis requires a low pH to maintain a relatively higher nisin activity. However, the acidic environment will result in cell arrest, and eventually decrease the relative nisin production. Hence, constructing an acid-resistant L. lactis is crucial for nisin harvest in acidic nisin fermentation. In this paper, the first discovery of the relationship between D-Asp amidation-associated gene (asnH) and acid resistance was reported. Overexpression of asnH in L. lactis F44 (F44A) resulted in a sevenfold increase in survival capacity during acid shift (pH 3) and enhanced nisin desorption capacity compared to F44 (wild type), which subsequently contributed to higher nisin production, reaching 5346 IU/mL, 57.0% more than that of F44 in the fed-batch fermentation. Furthermore, the engineered F44A showed a moderate increase in D-Asp amidation level (from 82 to 92%) compared to F44. The concomitant decrease of the negative charge inside the cell wall was detected by a newly developed method based on the nisin adsorption amount onto cell surface. Meanwhile, peptidoglycan cross-linkage increased from 36.8% (F44) to 41.9% (F44A), and intracellular pH can be better maintained by blocking extracellular H⁺ due to the maintenance of peptidoglycan integrity, which probably resulted from the action of inhibiting hydrolases activity. The inference was further supported by the acmC-overexpression strain F44C, which was characterized by uncontrolled peptidoglycan hydrolase activity. Our results provided a novel strategy for enhancing nisin yield through cell wall remodeling, which contributed to both continuous nisin synthesis and less nisin adsorption in acidic fermentation (dual enhancement).

Monensin and Nisin Affect Rumen Fermentation and Microbiota Differently In Vitro

Nisin, a bacteriocin, is a potential alternative to antibiotics to modulate rumen fermentation. However, little is known about its impacts on rumen microbes. This study evaluated the effects of nisin (1 and 5 μM) on in vitro rumen fermentation characteristics, microbiota, and select groups of rumen microbes in comparison with monensin (5 μM), one of the most commonly used ionophores in ruminants. Nisin had greater effects than monensin in inhibiting methane production and decreasing acetate/propionate ratio. Unlike monensin, nisin had no adverse effect on dry matter digestibility. Real-time PCR analysis showed that both monensin and nisin reduced the populations of total bacteria, fungi, and methanogens, while the population of protozoa was reduced only by monensin. Principal component analysis of bacterial 16S rRNA gene amplicons showed a clear separation between the microbiota shaped by monensin and by nisin. Comparative analysis also revealed a significant difference in relative abundance of some bacteria in different taxa between monensin and nisin. The different effects of monensin and nisin on microbial populations and bacterial communities are probably responsible for the discrepancy in their effects on rumen fermentation. Nisin may have advantages over monensin in modulating ruminal microbial ecology and reducing ruminant methane production without adversely affecting feed digestion, and thus it may be used as a potential alternative to monensin fed to ruminants.

Modeling growth of Alicyclobacillus acidoterrestris DSM 3922 type strain vegetative cells in the apple juice with nisin and lysozyme

In the present study, the effect of storage temperature on A. acidoterrestris DSM 3922 cells (10⁵ CFU/mL) was examined during growth in reconstituted apple juice (pH 3.8, °Brix 11.3) containing nisin (0-100 IU/mL) and lysozyme (0-100 mg/L). The growth curves were obtained at three temperatures of 27, 35 and 43 °C using absorbance data (OD_{600 nm}). Based on the results, the minimal inhibitory concentrations (MICs) of nisin were found as 10 IU/mL at all tested temperatures. On the other hand, increasing the temperature decreased the amount of lysozyme for growth inhibition. The MICs of lysozyme were found as 10, 2.5 and 1.25 mg/L at 27, 35 and 43 °C, respectively. At selected non-inhibitory doses, nisin (1.25-5 IU/mL) and lysozyme (0.3-2.5 mg/L) prolonged the lag time compared to the controls at the corresponding temperatures. In addition, there was a strong linear relationship between the lag time and lysozyme concentrations at 27 and 35 °C (R² > 0.98). The results of this study demonstrated that both nisin and lysozyme could be used to inhibit the growth of A. acidoterrestris cells in the apple juice. The results also indicated that the growth parameters were variable depending on the storage temperature and the type of the antimicrobial agent used in the apple juice.

Interactions of the antimicrobial peptide nisin Z with conventional antibiotics and the use of nanostructured lipid carriers to enhance antimicrobial activity

Antimicrobial resistance is an imminent threat to the effective prevention and treatment of bacterial infections and alternative antimicrobial strategies are desperately needed. Antimicrobial peptides (AMPs) may be promising alternatives to current antibiotics or act as adjuvants to enhance antibiotic potency. Additionally, the use of biodegradable lipid nanoparticles can enhance the antibacterial activity of antibiotics and antimicrobial peptides. In this study, the interaction of the AMPs, nisin Z and melittin, with conventional antibiotics was investigated on Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli. The effectiveness of nanostructured lipid carriers (NLCs) for the entrapment of nisin Z was also evaluated. Findings revealed that nisin Z exhibited additive interactions with numerous conventional antibiotics. Notable synergism was observed for novobiocin-nisin Z combinations. The addition of the non-antibiotic adjuvant EDTA significantly improved the antimicrobial activity of free nisin Z towards E.coli. NLCs containing nisin Z were effective against Gram-positive species at physiological pH, with an increase in effectiveness in the presence of EDTA. Results indicate that nisin Z may be advantageous as an adjuvant in antimicrobial chemotherapy, while contributing in the battle against antibiotic resistance. NLCs have the potential to enhance the antibacterial activity of nisin Z towards Gram-positive bacterial species associated with skin infections.

High-purity Nisin Alone or in Combination with Sodium Hypochlorite Is Effective against Planktonic and Biofilm Populations of Enterococcus faecalis

INTRODUCTION

Nisin, a broad-spectrum bacteriocin, has recently been highlighted for its biomedical applications. To date, no studies have examined the antimicrobial and antibiofilm properties of high-purity (>95%) nisin (nisin ZP) on Enterococcus faecalis and biofilms formed by this species. We hypothesize that nisin can inhibit E. faecalis and reduce biofilm biomass, and combinations of nisin and sodium hypochlorite (NaOCl) will enhance the antibiofilm properties against E. faecalis biofilms.

METHODS

Using broth cultures, disc diffusion assays, and biofilm assays, we examined the effects of nisin on various E. faecalis growth parameters and biofilm properties (biovolume, thickness, and roughness). Confocal microscopy was used in conjunction with Imaris and Comstat2 software (Kongens Lyngby, Copenhagen, Denmark) to measure and analyze the biofilm properties.

RESULTS

Nisin significantly decreased the growth of planktonic E. faecalis dose dependently. The minimum inhibitory concentrations against E. faecalis strains OG-1 and ATCC 29212 were 15 and 50 μg/mL, and the minimum bactericidal concentrations were 150 and 200 μg/mL, respectively. A reduction in biofilm biovolume and thickness was observed for biofilms treated with nisin at ≥10 μg/mL for 10 minutes. In addition, the combination of nisin with low doses of NaOCl enhanced the antibiofilm properties of both antimicrobial agents.

CONCLUSIONS

Nisin alone or in combination with low concentrations of NaOCl reduces the planktonic growth of E. faecalis and disrupts E. faecalis biofilm structure. Our results suggest that nisin has potential as an adjunctive endodontic therapeutic agent and as an alternative to conventional NaOCl irrigation.

Long-term antimicrobial effect of nisin released from electrospun triaxial fiber membranes

Electrospun membranes encapsulating nisin in the core of multi-layer coaxial fibers, with a hydrophobic PCL intermediate layer and a hygroscopic cellulose acetate sheath, have been demonstrated to provide long-term antimicrobial activity combined with a hygroscopic outer layer. Antimicrobial performance has been evaluated using modified versions of the antimicrobial textile test AATCC 100 and AATCC 147 against Staphylococcus aureus. The AATCC 147 tests indicate that antimicrobial activity persists up to 7days. The quantitative analysis from the AATCC 100 test indicates that tri-layer coaxial ("triaxial") electrospun fiber membranes provide >99.99% bacteria kill (4logkill) for up to five days. This indicates that the nisin-incorporated triaxial fibers have excellent biocidal activities for up to 5days and then provide biostatic activity for 2 or more days. Compared with other types of electrospun membranes, such as core-sheath coaxial ("coaxial") and single homogenous fibers, triaxial fiber membranes provided more robust and more sustained antimicrobial activity. Single fibers with nisin showed relatively weak activity and only for one day. Coaxial fiber membranes exhibited antimicrobial activity for a long period, but their biocidal activity was much weaker than that of triaxial fiber membranes, and only exhibited >99% bacteria kill (2logkill) after 1day of exposure.

STATEMENT OF SIGNIFICANCE

The increase in drug resistant pathogens has driven the need for alternative treatments that are effective against resistant bacteria and do not contribute to drug resistance. Nisin is an excellent model bacteriocin for antimicrobials because of its size and mode of action, and has been extensively used as FDA-approved food preservatives without any problematic resistance growth in bacteria during past decades. Nisin-containing fibers have been previously reported using conventional electrospinning but sustained antimicrobial effect has not been obtained. Here, we report the encapsulation of nisin into a multi-layered nanofiber construct using triaxial electrospinning in order to obtain a long-term antimicrobial activity. This will be highly beneficial in many applications, such as protective textiles, food packaging and cancer therapy.

Antimicrobial potential of bacteriocins in poultry and swine production

The routine use of antibiotics in agriculture has contributed to an increase in drug-resistant bacterial pathogens in animals that can potentially be transmitted to humans. In 2000, the World Health Organization identified resistance to antibiotics as one of the most significant global threats to public health and recommended that the use of antibiotics as additives in animal feed be phased out or terminated, particularly those used to treat human infections. Research is currently being carried out to identify alternative antimicrobial compounds for use in animal production. A number of studies, mostly in vitro, have provided evidence indicating that bacteriocins, which are antimicrobial peptides of bacterial origin, may be promising alternatives to conventional antibiotics in poultry and swine production. This review provides an update on bacteriocins and their potential for use in the poultry and swine industries.

Single-Molecule Sequencing (PacBio) of the Staphylococcus capitis NRCS-A Clone Reveals the Basis of Multidrug Resistance and Adaptation to the Neonatal Intensive Care Unit Environment

The multi-resistant Staphylococcus capitis clone NRCS-A has recently been described as a major pathogen causing nosocomial, late-onset sepsis (LOS) in preterm neonates worldwide. NRCS-A representatives exhibit an atypical antibiotic resistance profile. Here, the complete closed genome (chromosomal and plasmid sequences) of NRCS-A prototype strain CR01 and the draft genomes of three other clinical NRCS-A strains from Australia, Belgium and the United Kingdom are annotated and compared to available non-NRCS-A S. capitis genomes. Our goal was to delineate the uniqueness of the NRCS-A clone with respect to antibiotic resistance, virulence factors and mobile genetic elements. We identified 6 antimicrobial resistance genes, all carried by mobile genetic elements. Previously described virulence genes present in the NRCS-A genomes are shared with the six non-NRCS-A S. capitis genomes. Overall, 63 genes are specific to the NRCS-A lineage, including 28 genes located in the methicillin-resistance cassette SCCmec. Among the 35 remaining genes, 25 are of unknown function, and 9 correspond to an additional type I restriction modification system (n = 3), a cytosine methylation operon (n = 2), and a cluster of genes related to the biosynthesis of teichoic acids (n = 4). Interestingly, a tenth gene corresponds to a resistance determinant for nisin (nsr gene), a bacteriocin secreted by potential NRCS-A strain niche competitors in the gut microbiota. The genomic characteristics presented here emphasize the contribution of mobile genetic elements to the emergence of multidrug resistance in the S. capitis NRCS-A clone. No NRCS-A-specific known virulence determinant was detected, which does not support a role for virulence as a driving force of NRCS-A emergence in NICUs worldwide. However, the presence of a nisin resistance determinant on the NRCS-A chromosome, but not in other S. capitis strains and most coagulase-negative representatives, might confer a competitive advantage to NRCS-A strains during the early steps of gut colonization in neonates. This suggests that the striking adaptation of NRCS-A to the NICU environment might be related to its specific antimicrobial resistance and also to a possible enhanced ability to challenge competing bacteria in its ecological niche.

Nematode Peptides with Host-Directed Anti-inflammatory Activity Rescue Caenorhabditis elegans from a Burkholderia pseudomallei Infection

Burkholderia pseudomallei, the causative agent of melioidosis, is among a growing number of bacterial pathogens that are increasingly antibiotic resistant. Antimicrobial peptides (AMPs) have been investigated as an alternative approach to treat microbial infections, as generally, there is a lower likelihood that a pathogen will develop resistance to AMPs. In this study, 36 candidate Caenorhabditis elegans genes that encode secreted peptides of <150 amino acids and previously shown to be overexpressed during infection by B. pseudomallei were identified from the expression profile of infected nematodes. RNA interference (RNAi)-based knockdown of 12/34 peptide-encoding genes resulted in enhanced nematode susceptibility to B. pseudomallei without affecting worm fitness. A microdilution test demonstrated that two peptides, NLP-31 and Y43C5A.3, exhibited anti-B. pseudomallei activity in a dose dependent manner on different pathogens. Time kill analysis proposed that these peptides were bacteriostatic against B. pseudomallei at concentrations up to 8× MIC90. The SYTOX green assay demonstrated that NLP-31 and Y43C5A.3 did not disrupt the B. pseudomallei membrane. Instead, gel retardation assays revealed that both peptides were able to bind to DNA and interfere with bacterial viability. In parallel, microscopic examination showed induction of cellular filamentation, a hallmark of DNA synthesis inhibition, of NLP-31 and Y43C5A.3 treated cells. In addition, the peptides also regulated the expression of inflammatory cytokines in B. pseudomallei infected macrophage cells. Collectively, these findings demonstrate the potential of NLP-31 and Y43C5A.3 as anti-B. pseudomallei peptides based on their function as immune modulators.

Mode of action and membrane specificity of the antimicrobial peptide snakin-2

Antimicrobial peptides (AMPs) are a diverse group of short, cationic peptides which are naturally occurring molecules in the first-line defense of most living organisms. They represent promising candidates for the treatment of pathogenic microorganisms. Snakin-2 (SN2) from tomato (Solanum lycopersicum) is stabilized through six intramolecular disulphide bridges; it shows broad-spectrum antimicrobial activity against bacteria and fungi, and it agglomerates single cells prior to killing. In this study, we further characterized SN2 by providing time-kill curves and corresponding growth inhibition analysis of model organisms, such as E. coli or B. subtilis. SN2 was produced recombinantly in E. coli with thioredoxin as fusion protein, which was removed after affinity purification by proteolytic digestion. Furthermore, the target specificity of SN2 was investigated by means of hemolysis and hemagglutination assays; its effect on plant cell membranes of isolated protoplasts was investigated by microscopy. SN2 shows a non-specific pore-forming effect in all tested membranes. We suggest that SN2 could be useful as a preservative agent to protect food, pharmaceuticals, or cosmetics from decomposition by microbes.