Cloning, overexpression, purification of bacteriocin enterocin-B and structural analysis, interaction determination of enterocin-A, B against pathogenic bacteria and human cancer cells

Molecular Assessments of Antimicrobial Protein Enterocins and Quorum Sensing Genes and Their Role in Virulence of the Genus Enterococcus

Enterococcus has emerged as an opportunistic pathogen because of its antibiotic resistance and virulence profile, which makes it a causative agent of several diseases like endocarditis, surgical site, and urinary tract infections. Currently, species of this genus are the 2nd most frequently isolated microorganisms from hospital-acquired infections. Significant association with hospitals and unhygienic conditions of the environments has made them resistant to a wide range of antibiotics. On the brighter side, enterococci have the ability to produce antimicrobial proteins (i.e., enterocins) that exhibit wide antagonistic activity, thus making them useful microbes in the food and pharmaceutical industries. Enterocins are also involved in niche control in gut microbiota which is regulated by the quorum sensing (QS) system. A bacterial communication system that is controlled by the fsr operon in enterococci consists of FsrABDC, ef1097, and GelE/SprE genes. Hence, the present study was conducted for molecular assessment of enterocins and quorum sensing genes, inter-environmental correlation, and species prevalence of enterococci isolated from different environmental niches of Karachi, Pakistan. Obtained results revealed the highest prevalence of E. faecium and E. faecalis in all environments. Bacterial antagonism and enterocin genes were observed significantly high in poultry environments. The inter-environmental correlation indicated a strong positive correlation of freshwater with sewage and soil environments. Similarly, the fsr regulatory system was mostly identified in poultry-related environments, and a significant correlation between QS system and biofilm formation was established. In conclusion, this study confirmed the high prevalence of E. faecium in all tested sources, high enterocin production in non-clinical environments, and more fsr regulatory genes in poultry-related environments.

Study of an Enterococcus faecium strain isolated from an artisanal Mexican cheese, whole-genome sequencing, comparative genomics, and bacteriocin expression

Enterococci are ubiquitous microorganisms in almost all environments, from the soil we step on to the food we eat. They are frequently found in naturally fermented foods, contributing to ripening through protein, lipid, and sugar metabolism. On the other hand, these organisms are also leading the current antibiotic resistance crisis. In this study, we performed whole-genome sequencing and comparative genomics of an Enterococcus faecium strain isolated from an artisanal Mexican Cotija cheese, namely QD-2. We found clear genomic differences between commensal and pathogenic strains, particularly in their carbohydrate metabolic pathways, resistance to vancomycin and other antibiotics, bacteriocin production, and bacteriophage and CRISPR content. Furthermore, a bacteriocin transcription analysis performed by RT-qPCR revealed that, at the end of the log phase, besides enterocins A and X, two putative bacteriocins not reported previously are also transcribed as a bicistronic operon in E. faecium QD-2, and are expressed 1.5 times higher than enterocin A when cultured in MRS broth.

Antimicrobial Activity of Synthetic Enterocins A, B, P, SEK4, and L50, Alone and in Combinations, against Clostridium perfringens

Multidrug-resistant Clostridium perfringens infections are a major threat to the poultry industry. Effective alternatives to antibiotics are urgently needed to prevent these infections and limit the spread of multidrug-resistant bacteria. The aim of the study was to produce by chemical synthesis a set of enterocins of different subgroups of class II bacteriocins and to compare their spectrum of inhibitory activity, either alone or in combination, against a panel of twenty C. perfringens isolates. Enterocins A, P, SEK4 (class IIa bacteriocins), B (unsubgrouped class II bacteriocin), and L50 (class IId leaderless bacteriocin) were produced by microwave-assisted solid-phase peptide synthesis. Their antimicrobial activity was determined by agar well diffusion and microtitration methods against twenty C. perfringens isolates and against other pathogens. The FICINDEX of different combinations of the selected enterocins was calculated in order to identify combinations with synergistic effects. The results showed that synthetic analogs of L50A and L50B were the most active against C. perfringens. These peptides also showed the broadest spectrum of activity when tested against other non-clostridial indicator strains, including Listeria monocytogenes, methicillin-resistant Staphylococcus aureus, Streptococcus suis, Streptococcus pyogenes, Enterococcus cecorum, Enterococcus faecalis, as well as Gram-negative bacteria (Campylobacter coli and Pseudomonas aeruginosa), among others. The selected synthetic enterocins were combined on the basis of their different mechanisms of action, and all combinations tested showed synergy or partial synergy against C. perfringens. In conclusion, because of their high activity against C. perfringens and other pathogens, the use of synthetic enterocins alone or as a consortium can be a good alternative to the use of antibiotics in the poultry sector.

Application Value of Antimicrobial Peptides in Gastrointestinal Tumors

Gastrointestinal cancer is a common clinical malignant tumor disease that seriously endangers human health and lacks effective treatment methods. As part of the innate immune defense of many organisms, antimicrobial peptides not only have broad-spectrum antibacterial activity but also can specifically kill tumor cells. The positive charge of antimicrobial peptides under neutral conditions determines their high selectivity to tumor cells. In addition, antimicrobial peptides also have unique anticancer mechanisms, such as inducing apoptosis, autophagy, cell cycle arrest, membrane destruction, and inhibition of metastasis, which highlights the low drug resistance and high specificity of antimicrobial peptides. In this review, we summarize the related studies on antimicrobial peptides in the treatment of digestive tract tumors, mainly oral cancer, esophageal cancer, gastric cancer, liver cancer, pancreatic cancer, and colorectal cancer. This paper describes the therapeutic advantages of antimicrobial peptides due to their unique anticancer mechanisms. The length, net charge, and secondary structure of antimicrobial peptides can be modified by design or modification to further enhance their anticancer effects. In summary, as an emerging cancer treatment drug, antimicrobial peptides need to be further studied to realize their application in gastrointestinal cancer diseases.

Characterisation, slow-release, and antibacterial properties of carboxymethyl chitosan/inulin hydrogel film loaded with novel antilisterial durancin GL

This paper reports the development of a hydrogel film with antibacterial activity and controlled release characteristics. Carboxymethyl chitosan (CMCS) is grafted onto durancin GL and inulin via a mediated reaction between N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. Rheology tests, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy, and lap shear tests confirmed the formation of a stable chemical cross-linking and excellent adhesion hydrogel with 4 % CMCS and 8 % inulin. The CMCS/inulin hydrogel film loaded with durancin GL appears transparent and uniform. FTIR spectroscopy results reveal the interaction mode among CMCS, inulin, durancin GL, and the hydrogel film structure. Cross-linking improved thermal stability and water-vapour barrier performance. The hydrophobicity of CMCS/inulin @Durancin GL increased under a durancin GL concentration of 0.036 g/30 mL, and the release of active substances is prolonged. In-vitro antibacterial capacity and salmon preservation experiments show that the addition of durancin GL enhanced the antibacterial activity of the hydrogel film. Therefore, CMCS/inulin@Durancin GL hydrogel films can be used as fresh-keeping packaging materials in practical applications.

Probiotic-Derived Bioactive Compounds in Colorectal Cancer Treatment

Colorectal cancer (CRC) is a multifactorial disease with increased morbidity and mortality rates globally. Despite advanced chemotherapeutic approaches for the treatment of CRC, low survival rates due to the regular occurrence of drug resistance and deleterious side effects render the need for alternative anticancer agents imperative. Accumulating evidence supports that gut microbiota imbalance precedes the establishment of carcinogenesis, subsequently contributing to cancer progression and response to anticancer therapy. Manipulation of the gut microbiota composition via the administration of probiotic-derived bioactive compounds has gradually attained the interest of scientific communities as a novel therapeutic strategy for CRC. These compounds encompass miscellaneous metabolic secreted products of probiotics, including bacteriocins, short-chain fatty acids (SCFAs), lactate, exopolysaccharides (EPSs), biosurfactants, and bacterial peptides, with profound anti-inflammatory and antiproliferative properties. This review provides a classification of postbiotic types and a comprehensive summary of the current state of research on their biological role against CRC. It also describes how their intricate interaction with the gut microbiota regulates the proper function of the intestinal barrier, thus eliminating gut dysbiosis and CRC development. Finally, it discusses the future perspectives in precision-medicine approaches as well as the challenges of their synthesis and optimization of administration in clinical studies.

Genome sequencing of Enterococcus faecium NT04, an oral microbiota revealed the production of enterocin A/B active against oral pathogens

Objective

This study aimed to isolate and investigate a bacterium from an Egyptian adult's healthy oral cavity, focusing on its probiotic properties, especially its antagonistic activity against oral pathogens.

Methods

The isolated bacterium NT04 using 16S rRNA gene sequencing, was identified as Enterococcus faecium. In this study, the whole genome of Enterococcus faecium NT04 was sequenced and annotated by bioinformatics analysis tools.

Results

Numerous genes encoding the production of diverse metabolic and probiotic properties, such as bacteriocin-like inhibitory substances (Enterocin A and B), cofactors, antioxidants, and vitamins, were confirmed by genomic analysis. There were no pathogenicity islands or plasmid insertions found. This strain is virulent for host colonization rather than invasion.

Conclusion

Genomic characteristics of strain NT04 support its potentiality as an anti-oral pathogen probiotic candidate.

Biopreservative efficacy of Enterococcus faecium-immobilised film and its enterocin against Salmonella enterica

The growing awareness about the adverse health effects of artificial synthetic preservatives has led to a rapid increase in the demand for safe food preservation techniques and bio preservatives. Thus, in this study, the biopreservatives efficacy of enterocin-producing Enterococcus faecium Smr18 and its enterocin, ESmr18 was evaluated against Salmonella enterica contamination in chicken samples. E. faecium Smr18 is susceptible to the antibiotics penicillin-G, ampicillin, vancomycin, and erythromycin, thereby indicating that it is a nonpathogenic strain. Further, the enterocin ESmr18 was purified and characterised as a 3.8 kDa peptide. It possessed broad spectrum antibacterial activity against both Gram-positive and Gram-negative pathogens including S. enterica serotypes Typhi and Typhimurium. Purified ESmr18 disrupted the cell membrane permeability of the target cell thereby causing rapid efflux of potassium ions from L. monocytogenes and S. enterica. Chicken samples inoculated with S. enterica and packaged in alginate films containing immobilised viable E. faecium resulted in 3 log₁₀ colony forming units (CFU) reduction in the counts of S. enterica after 34 days of storage at 7-8 °C. The crude preparation of ESmr18 also significantly (p < 0.05) reduced the CFU counts of salmonella-inoculated chicken meat model. Purified ESmr18 at the concentration upto 4.98 µg/ml had no cytolytic effect against human red blood cells. Crude preparation of ESmr18 when orally administered in fish did not cause any significant (p < 0.05) change in the biochemical parameters of sera samples. Nonsignificant changes in the parameters of comet and micronucleus assays were observed between the treated and untreated groups of fishes that further indicated the safety profile of the enterocin ESmr18.

Targeting Enterococci with Antimicrobial Activity against Clostridium perfringens from Poultry

Necrotic enteritis (NE), caused by Clostridium perfringens, is an emerging issue in poultry farming. New approaches, other than antibiotics, are necessary to prevent NE development and the emergence of multidrug-resistant bacteria. Enterococci are commensal microorganisms that can produce enterocins, antimicrobial peptides with activities against pathogens, and could be excellent candidates for protective cultures. This study aimed to screen and characterize Enterococcus strains of poultry origin for their inhibitory activity against C. perfringens. In total, 251 Enterococcus strains of poultry origin plus five bacteriocin-producing (BP+) E. durans strains of other origins were screened for antimicrobial activity against the indicator C. perfringens X2967 strain using the "spot on the lawn" method. We detected thirty-two BP+ strains (eleven Enterococcus faecium, nine E. gallinarum, eight E. faecalis, three E. durans, and one E. casseliflavus). We further studied the antimicrobial activity of the supernatants of these 32 BP+ strains using agar well diffusion and microtitration against a collection of 20 C. perfringens strains. Twelve BP+ enterococci that were found to exhibit antimicrobial activity against C. perfringens were characterized using whole genome sequencing. Among these, E. faecium X2893 and X2906 were the most promising candidates for further studies as protective cultures for poultry farming. Both strains belong to the sequence type ST722, harbor the genes encoding for enterocin A and enterocin B, do not possess acquired resistance genes, do not carry plasmids, and present the acm gene, which is implicated in host colonization. Further research is needed to determine the utility of these strains as protective cultures.

Structural Features, Mechanisms of Action, and Prospects for Practical Application of Class II Bacteriocins

Bacteriocins are antimicrobial peptides ribosomally synthesized by both Gram-negative and Gram-positive bacteria, as well as by archaea. Bacteriocins are usually active against phylogenetically related bacteria, providing competitive advantage to their producers in the natural bacterial environment. However, some bacteriocins are known to have a broader spectrum of antibacterial activity, including activity against multidrug-resistant bacterial strains. Multitude of bacteriocins studied to date are characterized by a wide variety of chemical structures and mechanisms of action. Existing classification systems for bacteriocins take into account structural features and biosynthetic pathways of bacteriocins, as well as the phylogenetic affiliation of their producing organisms. Heat-stable bacteriocins with molecular weight of less than 10 kDa from Gram-positive and Gram-negative producers are divided into post-translationally modified (class I) and unmodified peptides (class II). In recent years there has been an increasing interest in the class II bacteriocins as potential therapeutic agents that can help to combat antibiotic-resistant infections. Advantages of unmodified peptides are relative simplicity of their biotechnological production in heterologous systems and chemical synthesis. Potential for the combined use of bacteriocins with other antimicrobial agents allowing to enhance their efficacy, low probability of cross-resistance development, and ability of probiotic strains to produce bacteriocins in situ make them promising candidate compounds for creation of new drugs. The review focuses on structural diversity of the class II bacteriocins and their practical relevance.

Antimicrobial peptides: features, applications and the potential use against covid-19

BACKGROUND

Antimicrobial peptides (AMPs) are a diverse class of molecules that represent a vital part of innate immunity. AMPs are evolutionarily conserved molecules that exhibit structural and functional diversity. They provide a possible solution to the antibiotic-resistance crisis.

MAIN TEXT

These small cationic peptides can target bacteria, fungi, and viruses, as well as cancer cells. Their unique action mechanisms, rare antibiotic-resistant variants, broad-spectrum activity, low toxicity, and high specificity encourage pharmaceutical industries to conduct clinical trials to develop them as therapeutic drugs. The rapid development of computer-assisted strategies accelerated the identification of AMPs. The Antimicrobial Peptide Database (APD) so far contains 3324 AMPs from different sources. In addition to their applications in different fields, some AMPs demonstrated the potential to combat COVID-19, and hinder viral infectivity in diverse ways.

CONCLUSIONS

This review provides a brief history of AMPs and their features, including classification, evolution, sources and mechanisms of action, biosynthesis pathway, and identification techniques. Furthermore, their different applications, challenges to clinical applications, and their potential use against COVID-19 are presented.

Role of microbial secreted proteins in gut microbiota-host interactions

The mammalian gut microbiota comprises a variety of commensals including potential probiotics and pathobionts, influencing the host itself. Members of the microbiota can intervene with host physiology by several mechanisms, including the secretion of a relatively well-reported set of metabolic products. Another microbiota influence mechanism is the use of secreted proteins (i.e., the secretome), impacting both the host and other community members. While widely reported and studied in pathogens, this mechanism remains understood to a lesser extent in commensals, and this knowledge is increasing in recent years. In the following minireview, we assess the current literature covering different studies, concerning the functions of secretable proteins from members of the gut microbiota (including commensals, pathobionts, and probiotics). Their effect on host physiology and health, and how these effects can be harnessed by postbiotic products, are also discussed.

Designing a novel fusion protein from Streptococcus agalactiae with apoptosis induction effects on cervical cancer cells

Cervical cancer remains life-threatening cancer in women around the world. Due to the limitations of conventional treatment approaches, there is an urgent need to develop novel and more efficient strategies against cervical cancer. Therefore, the researchers attend to the alternative anti-cancer compounds like bacterial products. Rib and α are known as surface proteins of Streptococcus agalactiae with immunologic effects. In the present study, we designed a new anti-cancer fusion protein (Rib-α) originating from S. agalactiae with in silico methods, and then, the recombinant gene was cloned in the pET-22 (+) expression vector. The recombinant protein was expressed in E. coli BL21. To purify the expressed protein, we applied the Ni-NTA column. The molecular mechanism by which Rib-α is cytotoxic to cancer cells has been discussed based on MTT, flow cytometry, and real-time PCR methods. The engineered fusion protein suppressed the proliferation of the cancer cells at 180 μg/ml. Cytotoxic assessment and morphological changes, augmentation of apoptotic-related genes, upregulation of caspase-3 mRNA, and flow cytometric analysis confirmed that apoptosis might be the principal mechanism of cell death. According to our findings, Rib-α fusion protein motivated the intrinsic apoptosis pathway. Therefore, it can be an exciting candidate to discover a new class of antineoplastic agents.

Thurincin H Is a Nonhemolytic Bacteriocin of Bacillus thuringiensis with Potential for Applied Use

Thurincin H, a bacteriocin produced by Bacillus thuringiensis, exhibits antibacterial activity against Gram-positive and Gram-negative bacteria. While much is known about its expression and antimicrobial spectrum, its hemolytic property has yet to be established. In this study, thurincin H was produced in a plasmid-free acrystalliferous strain of B. thuringiensis (Bt Cry^-B) that naturally lacked antimicrobial and hemolytic activities. When grown in Tryptic Soy Broth (TSB), the bacteriocin's maximal production in Bt Cry^-B harboring the thurincin H genetic cluster (Bt Cry^-B/pThur) was observed at 24 h. Thurincin H was purified as a sole peptide of ~5 kDa using three purification steps, i.e., salt precipitation, ultrafiltration, and gel filtration chromatography. The bacteriocin showed inhibitory activity against B. cereus (5631 U), Bt Cry^-B (8827 U), E. faecium wild type (11,197 U), and E. faecium ATCC 19,434 (6950 U), but not against Bt Cry^-B/pThurH and Bt Cry^-B/pThurHΔThnA. In addition, a minimum inhibitory concentration (MIC) of 5.0 μg/mL against B. cereus 183 was observed. In silico predictions suggested that thuricin H lacks hemolytic activity, which was validated in vitro using 4 × the MIC, i.e., 20 μg/ml. Our data lay a foundation for the potential safe use of thurincin H as an antibacterial peptide for medical use, in food products, and for expression in probiotic bacteria.

Biological Control of Acinetobacter baumannii: In Vitro and In Vivo Activity, Limitations, and Combination Therapies

The survival, proliferation, and epidemic spread of Acinetobacter baumannii (A. baumannii) in hospital settings is associated with several characteristics, including resistance to many commercially available antibiotics as well as the expression of multiple virulence mechanisms. This severely limits therapeutic options, with increased mortality and morbidity rates recorded worldwide. The World Health Organisation, thus, recognises A. baumannii as one of the critical pathogens that need to be prioritised for the development of new antibiotics or treatment. The current review will thus provide a brief overview of the antibiotic resistance and virulence mechanisms associated with A. baumannii’s “persist and resist strategy”. Thereafter, the potential of biological control agents including secondary metabolites such as biosurfactants [lipopeptides (surfactin and serrawettin) and glycolipids (rhamnolipid)] as well as predatory bacteria (Bdellovibrio bacteriovorus) and bacteriophages to directly target A. baumannii, will be discussed in terms of their in vitro and in vivo activity. In addition, limitations and corresponding mitigations strategies will be outlined, including curtailing resistance development using combination therapies, product stabilisation, and large-scale (up-scaling) production.

Functional and molecular characterization of a cold-active lipase from Psychrobacter celer PU3 with potential a*ntibiofilm property

The lipase gene from Psychrobacter celer PU3 was cloned into pET-28a(+) expression vector and overexpressed in E. coli BL21 (DE3) pLysS cells. The purified Psychrobacter celer lipase (PCL) was characterized as an alkaline active enzyme and has a molecular mass of around 30 kDa. The PCL was active even at a low temperature and the optimum range was observed between 10 and 40 °C temperatures. MALDI-TOF and phylogenetic analysis ensued that Psychrobacter celer PU3 lipase (PCL) was closely related to P. aureginosa lipase (PAL). MD simulation results suggests that temperature change did not affect overall structure of PCL, but it may alter temperature- dependent PCL structural changes. R₁ (129-135 AA) and R₂ (187-191 AA) regions could be important for temperature-dependent PCL function as they fluctuate much at 35 °C temperature. PMSF completely inhibited PCL lipase activity and it demonstrates the presence of serine residues in the active site of PCL. PCL is moderately halophilic and most of the tested organic solvents found to be inhibiting the lipase activity except the solvents ethanol and methanol. PCL activity was increased with surfactants (SDS and CTAB) and bleaching agents (hydrogen peroxide). The effect of different metal ions on PCL resulted that only mercuric chloride was found as the enhancer of the lipase activity. Antibiofilm property of PCL was evaluated against pathogenic Vibrio parahaemolyticus isolated from the diseased shrimp and MIC value was 500 U. PCL significantly altered the morphology and biofilm density of V. parahaemolyticus and the same was observed through scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) imaging. RT-PCR analysis revealed that the mRNA expression level of biofilm, colony morphology and major toxin-related (aphA, luxS, opaR, tolC, toxR) genes of V. parahaemolyticus were significantly downregulated with PCL treatment.

Advantages and disadvantages of non-starter lactic acid bacteria from traditional fermented foods: Potential use as starters or probiotics

Traditional fermented foods are a significant source of starter and/or non-starter lactic acid bacteria (nsLAB). Moreover, these microorganisms are also known for their role as probiotics. The potential of nsLAB is huge; however, there are still challenges to be overcome with respect to characterization and application. In the present review, the most important steps that autochthonous lactic acid bacteria isolated from fermented foods need to overcome, to qualify as novel starter cultures, or as probiotics, in food technology and biotechnology, are considered. These different characterization steps include precise identification, detection of health-promoting properties, and safety evaluation. Each of these features is strain specific and needs to be accurately determined. This review highlights the advantages and disadvantages of nsLAB, isolated from traditional fermented foods, discussing safety aspects and sensory impact.

Comparative Metabolomics Analyses of Plantaricin Q7 Production by Lactobacillus plantarum Q7

Plantaricin Q7 is a bacteriocin produced by Lactobacillus plantarum Q7 with food preservation potential. Low yield is one of the bottlenecks of the wide application of plantaricin Q7. Nontargeted metabolomics was performed to reveal the mechanism of plantaricin Q7 biosynthesis. The results showed that the composition and abundance of intracellular metabolites varied significantly at key time points of plantaricin Q7 synthesis. Differential metabolic pathways were purine metabolism; pyrimidine metabolism; alanine, aspartate, and glutamate metabolism; amino acid biosynthesis; aminoacyl-tRNA biosynthesis; and ABC transporters. Differential metabolites were xanthine, deoxyadenosine, uracil, 5-methylcytosine, α-ketoglutarate, γ-aminobutyric acid, glutamate, glutamine, and tryptophan. Based on metabolomics information, the putative metabolic synthesis pathway of plantaricin Q7 was proposed. Glutamine, glutamate, and 5-methylcytosine could be critical metabolites and simulate plantaricin Q7 biosynthesis significantly (P < 0.05). Bacteriocin production was investigated by comparative metabolomics in this report, which could help to achieve higher plantaricin Q7 yield by metabolic regulation.

Exploring the cytotoxic mechanisms of Pediocin PA-1 towards HeLa and HT29 cells by comparison to known bacteriocins: Microcin E492, enterocin heterodimer and Divercin V41

The purpose of this study was to explore potential mechanisms of cytotoxicity towards HeLa and HT29 cells displayed by Pediocin PA-1. We did this by carrying out sequence alignments and 3D modelling of related bacteriocins which have been studied in greater detail: Microcin E492, Enterocin AB heterodimer and Divercin V41. Microcin E492 interacts with Toll-Like Receptor 4 in order to activate an apoptosis reaction, sequence alignment showed a high homology between Pediocin PA-1 and Microcin E492 whereas 3D modelling showed Pediocin PA-1 interacting with TLR-4 in a way reminiscent of Microcin E492. Furthermore, Pediocin PA-1 had the highest homology with the Enterocin heterodimer, particularly chain A; Enterocin has also shown to cause an apoptotic response in cancer cells. Based on this we are led to strongly believe Pediocin PA-1 interacts with TLRs in order to cause cell death. If this is the case, it would explain the difference in cytotoxicity towards HeLa over HT29 cells, due to difference in expression of particular TLRs. Overall, we believe Pediocin PA-1 exhibits a dual effect which is dose dependant, like that of Microcin. Unfortunately, due to the COVID-19 pandemic, we were unable to carry out experiments in the lab, and the unavailability of important data meant we were unable to provide and validate out solid conclusions, but rather suggestions. However, bioinformatic analysis is still able to provide information regarding structure and sequence analysis to draw plausible and evidence based conclusions. We have been able to highlight interesting findings and how these could be translated into future research and therapeutics in order to improve the quality of treatment and life of cancer patients.

Looking into key bacterial proteins involved in gut dysbiosis

The gastrointestinal microbiota plays a pivotal role in health and has been linked to many diseases. With the rapid accumulation of pyrosequencing data of the bacterial composition, the causal-effect relationship between specific dysbiosis features and diseases is now being explored. The aim of this review is to describe the key functional bacterial proteins and antigens in the context of dysbiosis related-diseases. We subjectively classify the key functional proteins into two categories: Primary key proteins and secondary key proteins. The primary key proteins mainly act by themselves and include biofilm inhibitors, toxin degraders, oncogene degraders, adipose metabolism modulators, anti-inflammatory peptides, bacteriocins, host cell regulators, adhesion and invasion molecules, and intestinal barrier regulators. The secondary key proteins mainly act by eliciting host immune responses and include flagellin, outer membrane proteins, and other autoantibody-related antigens. Knowledge of key bacterial proteins is limited compared to the rich microbiome data. Understanding and focusing on these key proteins will pave the way for future mechanistic level cause-effect studies of gut dysbiosis and diseases.

The Increasing Issue of Vancomycin-Resistant Enterococci and the Bacteriocin Solution

Enterococci are commensals of human and other animals’ gastrointestinal tracts. Only making up a small part of the microbiota, they have not played a significant role in research, until the 1980s. Although the exact year is variable according to different geographical areas, this was the decade when vancomycin-resistant enterococci (VRE) were discovered and since then their role as causative agents of human infections has increased. Enterococcus faecium is on the WHO’s list of “bacteria for which new antibiotics are urgently needed,” and with no new antibiotics in development, the situation is desperate. In this review, different aspects of VRE are outlined, including the mortality caused by VRE, antibiotic resistance profiles, animal-modeling efforts, and virulence. In addition, the limitations of current antibiotic treatments for VRE and prospective new treatments, such as bacteriocins, are reviewed.

Anticancer Effect of Enterocin A-Colicin E1 Fusion Peptide on the Gastric Cancer Cell

Cancer is one of the most causes of death all over the world, although improvements in its treatment and recognition. Due to the limitations of common anticancer methods, including surgery, chemotherapy, and radiotherapy, attention has been drawn to other anti-cancer compounds, especially natural peptides such as bacteriocins. In this study, we used a combination of two bacteriocins, colicin E1 and enterocin A, against AGS gastric cancer cell lines. In order to evaluate anticancer properties of fusion peptide, we applied MTT assay, real-time PCR, and flow cytometry tests. This is the first report to show the cell growth inhibitory activity of the enterocin A in combination with colicin E1 against AGS human cancer cells. The results of this study showed that this fusion peptide at a concentration of 60.4 µg/mL and 24 h was able to kill half of the tested cancer cells, and treatment of the cells with this concentration increased the expression of bax and caspase 3 genes and reduced the expression of bacl-2 in 24 h. Flow cytometry analysis of annexin V-FITC/propidium iodide results also showed that our peptide was able to induce apoptosis in treated cells compared with control. Taken together, enterocin A-colicin E1 (ent A-col E1) can be considered as a good candidate for anticancer therapies.

Genome Mining for Antimicrobial Compounds in Wild Marine Animals-Associated Enterococci

New ecosystems are being actively mined for new bioactive compounds. Because of the large amount of unexplored biodiversity, bacteria from marine environments are especially promising. Further, host-associated microbes are of special interest because of their low toxicity and compatibility with host health. Here, we identified and characterized biosynthetic gene clusters encoding antimicrobial compounds in host-associated enterococci recovered from fecal samples of wild marine animals remote from human-affected ecosystems. Putative biosynthetic gene clusters in the genomes of 22 Enterococcus strains of marine origin were predicted using antiSMASH5 and Bagel4 bioinformatic software. At least one gene cluster encoding a putative bioactive compound precursor was identified in each genome. Collectively, 73 putative antimicrobial compounds were identified, including 61 bacteriocins (83.56%), 10 terpenes (13.70%), and 2 (2.74%) related to putative nonribosomal peptides (NRPs). Two of the species studied, Enterococcus avium and Enterococcus mundtti, are rare causes of human disease and were found to lack any known pathogenic determinants but yet possessed bacteriocin biosynthetic genes, suggesting possible additional utility as probiotics. Wild marine animal-associated enterococci from human-remote ecosystems provide a potentially rich source for new antimicrobial compounds of therapeutic and industrial value and potential probiotic application.

Bacteriocins: New Potential Therapeutic Candidates in Cancer Therapy

Cancer is one of the most important disorders which is associated with high mortality and high costs of treatment for patients. Despite several efforts, finding, designing and developing, new therapeutic platforms in the treatment of cancer patients are still required. Utilization of microorganisms, particularly bacteria has emerged as new therapeutic approaches in the treatment of various cancers. Increasing data indicated that bacteria could be used in the production of a wide range of anti-cancer agents, including bacteriocins, antibiotics, peptides, enzymes, and toxins. Among these anti-cancer agents, bacteriocins have attractive properties, which make them powerful anti-cancer drugs. Multiple lines evidence indicated that several bacteriocins (i.e., colcins, nisins, pediocins, pyocins, and bovocins) via activation/inhibition different cellular and molecular signaling pathways are able to suppress tumor growth in various stages. Hence, identification and using various bacteriocins could lead to improve and introduce them to clinical practices. Here, we summarized various bacteriocins which could be employed as anti-cancer agents in the treatment of many cancers.

Antimicrobial peptides against colorectal cancer-a focused review

Despite recent advances in the treatment of colorectal cancer (CRC), low patient survival rate due to emergence of drug resistant cancer cells, metastasis and multiple deleterious side effects of chemotherapy, is a cause of public concern globally. To negate these clinical conundrums, search for effective and harmless novel molecular entities for the treatment of CRC is an urgent necessity. Since antimicrobial peptides (AMPs) are part of innate immunity of living beings, it is quite imperative to look for essential attributes of these peptides which may contribute to their effectiveness against carcinogenesis. Once identified, those characteristics can be suitably modified using several synthetic and computational techniques to further enhance their selectivity and pharmacokinetic profiles. Hence, this review analyses scientific reports describing the antiproliferative action of AMPs derived from several sources, particularly focusing on various colon cancer in vitro/in vivo investigations. On perusal of the literature, it appears that AMPs based therapeutics would definitely find special place in CRC therapy in future either alone or as an adjunct to chemotherapy provided some necessary alterations are made in their natural structures to make them more compatible with modern clinical practice. In this context, further in-depth research is warranted in adequate in vivo models.

Probiotic characterization of bacterial strains from fermented South Indian tomato pickle and country chicken intestine having antioxidative and antiproliferative activities

AIM

The present study aims to evaluate the potential antioxidant and antiproliferative properties of probiotic bacterial isolates Weissella cibaria p3B, Bacillus subtilis CS, and Bacillus tequilensis CL, isolated from South Indian fermented tomato pickle (homemade) and gut content of indigenous country chicken.

METHODS AND RESULTS

The bacterial isolates exhibited antimicrobial activity against food-borne, human pathogenic bacteria, along with better survival under different bile and acidic conditions, hydrophobicity towards several hydrocarbons, and adherence to intestinal epithelial cells (INT-407 cells). Also, the intact cell (IC) mixture of the three species showed better DPPH, ABTS, and Fe²⁺ chelating activity as compared to the individual IC or cell extract (CE) activity. Among the three bacterial species, W. cibaria p3B revealed maximum antiproliferative activity against HeLa and Caco-2 cancer cells, all of which were nontoxic to INT-407 cells. Apart from being non-hemolytic, the bacterial isolates did not display any necrotic inhibition in HeLa and Caco-2 cells. The cell free supernatant (CFS) of the three bacterial isolates were tested for the production of antimicrobial peptides or bacteriocins. It found that the CFS of bacterial isolates was stable at various temperature, pH and sensitive to proteolytic enzymes confirms protenoius in nature of the antimicrobil peptides or bacteriocins.

CONCLUSION

The bacterial isolates showed promising antimicrobial, antioxidant as well as antiproliferative activities with better survival ability at different pH and bile concentrations. The three bacterial isolates were able to produce potential antimicrobial peptides or bacteriocins.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results indicate better compatibility of our bacterial isolates against synthetic drugs to avoid adverse side effects and can be processed as dietary supplements against food and human pathogens. They can also provide antioxidative and antiproliferative benefits to humans and animals.

Characterization, modes of action, and application of a novel broad-spectrum bacteriocin BM1300 produced by Lactobacillus crustorum MN047

Bacteriocins are ribosomally synthesized peptides with antibacterial activity against food-borne pathogenic bacteria that cause spoilage, possessing important potential for use as a natural preservative in the food industry. The novel bacteriocin BM1300 produced by Lactobacillus crustorum MN047 was identified after purification in this study. It displayed broad-spectrum antibacterial activity against some selected Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) values of BM1300 against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 were 13.4 μg/mL and 6.7 μg/mL, respectively. Moreover, BM1300 showed excellent thermal (between 60 and 120 °C), pH (2-11), and chemical (Tween-40, Tween-80, Triton X-100, and EDTA) stabilities. Time-kill curves revealed that BM1300 exhibited bactericidal activity against S. aureus and E. coli. The scanning and transmission electron microscopy indicated that BM1300 acted by disrupting the cell membrane integrity and increasing cell membrane permeabilization of indicator bacteria. The disruption of cell membrane integrity caused by BM1300 was further demonstrated by the uptake of propidium iodide (PI) and the release of intracellular lactate dehydrogenase (LDH) and nucleic acid and proteins. Moreover, BM1300 affected cell cycle distribution to exert antibacterial activity collaboratively. Meanwhile, BM1300 inhibited the growth of S. aureus and E. coli of beef meat and improved the microbiological quality of beef meat. These findings place BM1300 as a potential biopreservative in the food industry.

Mutagenicity and genotoxicity assessment of a new biopreservative product rich in Enterocin AS-48

A biopreservative derived from the fermentation of a dairy byproduct by Enterococcus faecalis UGRA10 strains being developed. This product possesses a strong and wide antibacterial spectrum mainly due to the presence of Enterocin AS-48 in its composition. To assess its potential as food additive, the mutagenicicity and genotoxicity has been assayed by means of the bacterial reverse-mutation assay in Salmonella typhimurium TA97A, TA98, TA100, TA102, TA1535 strains (Ames test, OECD 471, 2020) and the micronucleus test (MN) (OECD 487, 2016) in L5178Y/Tk ± cells. The results in the Ames test after exposure to the byproduct (6.75-100 μg/plate) with absence and presence of the metabolic activation system from rat liver (S9 fraction), revealed not mutagenicity at the conditions tested. For the MN test, the exposition to five enterocin AS-48 concentrations (0.2-1 μg/μl) was tested in the absence and presence of S9 fraction, with no evidence of genotoxicity. Negative results in the mutagenicity and genotoxicity assays point out the good safety profile of the byproduct and support its use as additive. Further toxicological studies are required before its approval and commercial application.

Exploiting Zebrafish Xenografts for Testing the in vivo Antitumorigenic Activity of Microcin E492 Against Human Colorectal Cancer Cells

One of the approaches to address cancer treatment is to develop new drugs not only to obtain compounds with less side effects, but also to have a broader set of alternatives to tackle the resistant forms of this pathology. In this regard, growing evidence supports the use of bacteria-derived peptides such as bacteriocins, which have emerged as promising anti-cancer molecules. In addition to test the activity of these molecules on cancer cells in culture, their in vivo antitumorigenic properties must be validated in animal models. Although the standard approach for such assays employs experiments in nude mice, at the initial stages of testing, the use of high-throughput animal models would permit rapid proof-of-concept experiments, screening a high number of compounds, and thus increasing the possibilities of finding new anti-cancer molecules. A validated and promising alternative animal model are zebrafish larvae harboring xenografts of human cancer cells. Here, we addressed the anti-cancer properties of the antibacterial peptide microcin E492 (MccE492), a bacteriocin produced by Klebsiella pneumoniae, showing that this peptide has a marked cytotoxic effect on human colorectal cancer cells in vitro. Furthermore, we developed a zebrafish xenograft model using these cells to test the antitumor effect of MccE492 in vivo, demonstrating that intratumor injection of this peptide significantly reduced the tumor cell mass. Our results provide, for the first time, evidence of the in vivo antitumoral properties of a bacteriocin tested in an animal model. This evidence strongly supports the potential of this bacteriocin for the development of novel anti-cancer therapies.

Cytotoxicity, Pro-apoptotic Activity and in silico Studies of Dithiocarbamates and their Structure Based Design and SAR Studies

Background:

Cancer is a far-reaching and lethal but curable disease. Researchers have investigated numerous anticancer agents with only a few commercially available effective drugs which are very costly.

Objective:

Herein, we report the synthesis , characterization and anti cancer assays of a series of novel dithiocarbamates derivatives.

Methods:

All compounds were synthesized from different secondary amines and substituted benzyl chlorides in a single step. The structures of newly synthesized dithiocarbamate derivatives were confirmed by spectroscopic techniques (IR, NMR and HR-MS).

Results:

The synthesized compounds showed a significant anti-proliferative effect in cancer cells (HeLa) with the maximum inhibitory activity of compound SHD-2 with an IC50 = 0.31 ± 0.09 μM. However, the same compound exhibited 19.2% inhibition towards Baby Hamster Kidney fibroblasts (BHK-21), normal cell lines. Moreover, quantification of cellular DNA by flow cytometry for the evaluation of pro-apoptotic activity in HeLa cells demonstrates that arrest in cell cycle along with apoptosis advance towards drug cytotoxicity. However, molecular docking studies of the potent compound suggested that it binds to the major groove of the DNA.

Conclusion:

The cytotoxic and pro-apoptotic potential of the potent inhibitor may be further investigated in the animal models to advance their anti-cancer prospective.

Advanced strategies for combating bacterial biofilms

Biofilms are communities of microorganisms that are formed on and attached to living or nonliving surfaces and are surrounded by an extracellular polymeric material. Biofilm formation enjoys several advantages over the pathogens in the colonization process of medical devices and patients' organs. Unlike planktonic cells, biofilms have high intrinsic resistance to antibiotics and sanitizers, and overcoming them is a significant problematic challenge in the medical and food industries. There are no approved treatments to specifically target biofilms. Thus, it is required to study and present innovative and effective methods to combat a bacterial biofilm. In this review, several strategies have been discussed for combating bacterial biofilms to improve healthcare, food safety, and industrial process.

Preclinical studies of toxicity and safety of the AS-48 bacteriocin

The in vitro antimicrobial potency of the bacteriocin AS-48 is well documented, but its clinical application requires investigation, as its toxicity could be different in in vitro (haemolytic and antibacterial activity in blood and cytotoxicity towards normal human cell lines) and in vivo (e.g. mice and zebrafish embryos) models. Overall, the results obtained are promising. They reveal the negligible propensity of AS-48 to cause cell death or impede cell growth at therapeutic concentrations (up to 27 μM) and support the suitability of this peptide as a potential therapeutic agent against several microbial infections, due to its selectivity and potency at low concentrations (in the range of 0.3-8.9 μM). In addition, AS-48 exhibits low haemolytic activity in whole blood and does not induce nitrite accumulation in non-stimulated RAW macrophages, indicating a lack of pro-inflammatory effects. The unexpected heightened sensitivity of zebrafish embryos to AS-48 could be due to the low differentiation state of these cells. The low cytotoxicity of AS-48, the absence of lymphocyte proliferation in vivo after skin sensitization in mice, and the lack of toxicity in a murine model support the consideration of the broad spectrum antimicrobial peptide AS-48 as a promising therapeutic agent for the control of a vast array of microbial infections, in particular, those involved in skin and soft tissue diseases.