Bacteriocins: An Overview of Antimicrobial, Toxicity, and Biosafety Assessment by in vivo Models

The world of phage tail-like bacteriocins: State of the art and biotechnological perspectives

In the struggle for resources, bacteria have developed different systems of competition, including the type VI secretion system (T6SS) and phage tail-like bacteriocins (PTLBs), that act by killing other bacterial species or strains from the same species. The emergence of antimicrobial resistance (AMR) is an urgent global health problem. In this context, the need to develop new antimicrobial agents has put PTLBs in the spotlight. This review focuses on the most relevant aspects of PTLBs such as their structural features, biology, the technological tools to improve their application, and the most importantly their patents.

Characterization of a novel virulent mycobacteriophage Kashi-SSH1 (KSSH1) depicting genus-specific broad-spectrum anti-mycobacterial activity

AIM

Tuberculosis (TB) is one of the leading infectious disease causing mortality in the world and the rise of drug resistance; multi-drug resistance (MDR) and extensive-drug resistance (XDR) has added to extra complicacy of the disease. In this scenario, phage therapy has emerged as a potential treatment option against drug-sensitive/-resistant strains.

MATERIALS AND METHODS

The mycobacteriophage Kashi-SSH1 (KSSH1) was isolated from soil sample and was genomically, phenotypically, and functionally characterized. It includes genome assembly/annotation, transmission electron microscopy, multiplicity of infection (MOI), one-step growth curve, temperature/pH stability, confocal microscopy, host range determination and host growth reduction assays.

KEY FINDINGS

KSSH1 is a novel polyvalent virulent mycobacteriophage from the Myoviridae family, classified under cluster C1 with a 155,659 bp genome carrying key lysis genes-Holliday junction resolvase, Holin, Lysin A, and Lysin B, has an optimal MOI of 0.01, a 60-min latent period, and a burst size of 200 phages/bacterial cell. It remains stable up to 55 °C and within pH 7-10, exhibiting broad-spectrum activity against Mycobacterium species, like M. fortuitum (opportunistic pathogen), M. tuberculosis H37Ra (attenuated pathogen), and M. smegmatis, but not non-mycobacterial hosts. KSSH1 exhibits comparable growth inhibition of M. smegmatis like the antibiotics isoniazid and rifampicin as compared to the control, in liquid cultures for over 50 h without regrowth.

SIGNIFICANCE

KSSH1 exhibits strong lytic activity against various Mycobacterium species, lacks lysogeny-associated genes like integrases/transcriptional repressors, antibiotic resistance and virulence genes and remains stable from 4 °C to 37 °C and pH 8-10 ensuring safety/stability making it an ideal candidate for therapeutic use.

Phenotyping the Chemical Communications of the Intestinal Microbiota and the Host: Secondary Bile Acids as Postbiotics

The current definition of a postbiotic is a "preparation of inanimate microorganisms and/or their components that confers a health benefit on the host". Postbiotics can be mainly classified as metabolites, derived from intestinal bacterial fermentation, or structural components, as intrinsic constituents of the microbial cell. Secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA) are bacterial metabolites generated by the enzymatic modifications of primary bile acids by microbial enzymes. Secondary bile acids function as receptor ligands modulating the activity of a family of bile-acid-regulated receptors (BARRs), including GPBAR1, Vitamin D (VDR) receptor and RORγT expressed by various cell types within the entire human body. Secondary bile acids integrate the definition of postbiotics, exerting potential beneficial effects on human health given their ability to regulate multiple biological processes such as glucose metabolism, energy expenditure and inflammation/immunity. Although there is evidence that bile acids might be harmful to the intestine, most of this evidence does not account for intestinal dysbiosis. This review examines this novel conceptual framework of secondary bile acids as postbiotics and how these mediators participate in maintaining host health.

Isolation and characterization of antimicrobial peptides from Lactobacillus: Exploring mechanisms of action

The rise of antibiotic-resistant bacteria necessitates the development of novel antimicrobial agents. In this study, antimicrobial peptides (AMPs) were isolated from Lactobacillus sp., yielding Bioactive Peptide I (BAP I) and Bioactive Peptide III (BAP III). Purified via gel filtration chromatography (GFC), these peptides were characterized by MALDI-TOF MS and SDS-PAGE, which confirmed their molecular masses as 4168.14 Da and 8076.45 Da, respectively, and verified their high purity. Both peptides demonstrated potent antibacterial activity against Pseudomonas aeruginosa, Streptococcus sanguinis, Bacillus cereus, and Staphylococcus aureus, with BAP I exhibiting superior efficacy. This enhanced activity is likely due to its amphipathic structure and hydrophobic C-terminal region, which promote effective bacterial membrane disruption as evidenced by FE-SEM imaging. In addition to compromising membrane integrity, both BAP I and BAP III inhibited bacterial DNA polymerase activity, as shown by reduced PCR product formation. Complementary Circular Dichroism (CD) spectroscopy analysis indicated that peptide binding induced conformational changes in Taq polymerase, reducing its α-helical and β-sheet content while increasing the proportion of random coil structures-thus enhancing the enzyme's flexibility. Molecular docking and dynamics studies further revealed stable interactions between the peptides and the enzyme, suggesting a dual mechanism of action that targets both the bacterial membrane and DNA replication processes. Collectively, these findings highlight the significant potential of BAP I and BAP III as novel antimicrobial agents against multidrug-resistant infections. Future research should focus on evaluating their safety and clinical efficacy, as well as exploring their synergistic potential with existing antibiotics to advance these peptides as therapeutic alternatives.

How pathogens drive adipose tissue loss in the host

Weight loss is a hallmark of many infections, including those caused by bacteria, fungi and parasites. This loss is often attributed to infection-induced anorexia and the need to mobilise energy from internal sources to cope with the pathogens. Weight loss during infection results from a significant reduction of muscle and fat mass, two organs that together account for approximately 60% of body mass in the healthy state. While muscle wasting is a well-documented aspect of infection-related weight loss, adipose tissue loss via lipolysis also plays a critical role and can determine disease outcomes. This review explores the regulators of adipose tissue depletion via excessive lipolysis during infection, the probable mechanisms, and the potential consequences for host survival and pathogen fitness.

Lactobacillus acidophilus (strain Scav) postbiotic metabolites reduce infection and modulate inflammation in an in vivo model of Pseudomonas aeruginosa wound infection

AIMS

This study assessed the antibacterial, antibiofilm, and immunomodulatory activity of Lactobacillus acidophilus (strain Scav) postbiotic (LaP) in a mouse model of Pseudomonas aeruginosa wound infection and evaluated the bioactive components of the LaP.

METHODS AND RESULTS

LaP was tested for Pseudomonas aeruginosa clearance and immunomodulatory activity during wound infection. We show that LaP applied 1 h after infection reduced tissue bacterial burden within 24 h, and this reduction persisted for 5 days. Ciprofloxacin given once at the exact same time did not reduce bacteria load as compared to vehicle controls. LaP reduced plasma IL-6 and MCP-1 levels after 5 days. Wound tissue IL-6 and MCP-1 levels were increased in infected vehicle mice at 5 days, but tissues from LaP-treated mice were similar to sham controls. LaP increased tissue IL-10 (antiinflammatory cytokine) levels. Ciprofloxacin decreased plasma and tissue IL-6 compared to vehicle controls but did not affect MCP-1 or IL-10 levels. To elucidate antibacterial and antibiofilm metabolite(s) in LaP, fractionation followed by Ps. aeruginosa antagonistic activity assays were performed. This was followed by liquid chromatography coupled to mass spectrometry (LCMS) analysis. Our analyses identified a low molecular weight, polar molecule, which had both antibacterial and antibiofilm activity.

CONCLUSIONS

Lactobacillus acidophilus secretes an antibacterial and antibiofilm metabolite that reduced pathogen burden and resolved systemic inflammation in a Pseudomonas aeruginosa wound infection model.

Macromolecular interaction mechanism of the bacteriocin EntDD14 with the receptor binding domain (RBD) for the inhibition of SARS-CoV-2 and the JN.1 variant: Biomedical study based on elastic networks, stochastic Markov models, and macromolecular volumetric analysis

Bacteriocins, a class of molecules produced by bacteria, exhibit potent antimicrobial properties, including antiviral activities. The urgent need for treatments against SARS-CoV-2 has proposed bacteriocins such as enterocin DD14 (EntDD14) as potential therapeutic agents. However, the mechanism of macromolecular interaction of EntDD14 for the inhibition of SARS-CoV-2 is not yet fully understood, and its efficacy against variants like JN.1 has not been completely established. To address these knowledge gaps, biocomputational analyses were employed using a diverse set of tools, including Markov state models and volumetric analyses. This analysis revealed a favorable interaction between EntDD14 and the receptor-binding domain (RBD) of SARS-CoV-2. Furthermore, it was found that EntDD14 induces changes in the flexibility of the RBD and alters the distribution and size of its internal cavities, particularly in the JN.1 variant. These findings align with experimental observations and support the inhibitory mechanism of EntDD14 against SARS-CoV-2. Additionally, they suggest that EntDD14 may possess a broader spectrum of action, encompassing the JN.1 variant. This study paves the way for future investigations and therapeutic applications, encouraging further exploration of the antiviral activity of bacteriocins like EntDD14 against variants of concern like JN.1. However, additional experimental demonstrations are warranted to substantiate these findings.

Development of plantaricin RX-8 loaded pectin/4-carboxyphenylboric acid/carboxymethyl chitosan hydrogel microbead: A potential targeted oral delivery system

Bacteriocin can effectively improve the gut inflammation for their superior antibacterial activity. However, its inherent attributes, such as easily degraded and off-target effect in the gastrointestinal environment, make bacteriocins' efficient oral delivery a great challenge. Herein, a pectin/4-carboxyphenylboric acid/carboxymethyl chitosan (PEC/CPBA/CMCS) hydrogel microbead targeted oral delivery system was innovatively developed for the plantaricin RX-8 protective delivery, precisely targeted inflammatory microenvironment (IME) and sustained released plantaricin RX-8 by pH/ROS dual stimulation response. The hydrogel microbeads showed regular in shape and size, and exhibited high affinity for sialic acid of tumor cells. Subsequently, hydrogel microbeads exhibited the protective effect in gastrointestinal tract to avoid plantaricin RX-8 leakage, whereas in simulated normal environment and simulated IME showed better swelling and sustain release behaviors. Notably, the plantaricin RX-8 retains antibacterial activity in the simulated environments. Importantly, hydrogel microbeads showed no toxicity and inhibited tumor cell proliferation, which was ascribed to the sustained release of plantaricin RX-8 under ROS-sensitive IME, as validated by in vivo fluorescence imaging. Microbead not only demonstrated biodistribution in high potency, but also exhibited remarkable anti-inflammatory properties in alleviating colitis in vivo. The present study highlights the promising application of hydrogel carriers for improved oral delivery approach of bacteriocin bioavailability.

In silico analysis of bacteriocins from Lactobacillus acidophilus membrane vesicles against Streptococcus mutans GtfB protein

Oral pathogens pose a significant global health concern, affecting 80% of the world's population across all age groups. Among these pathogens, Streptococcus mutans stands out as a prominent threat. The rise in antibiotic resistance has limited the effectiveness of conventional antibiotics. In contrast, probiotics produce antibacterial peptides known as bacteriocins, which exhibit inhibitory effects against closely related and even unrelated bacterial species. Specifically, Lactobacillus acidophilus bacteriocins are encapsulated within membrane vesicles (MVs), allowing for long-distance transport and targeted delivery. However, no prior studies have investigated L. acidophilus membrane MV-encapsulated bacteriocins against S. mutans. In this study, we employed in-silico methods to target bacteriocins from MVs of L. acidophilus, against the GtfB virulence protein of S. mutans. Our findings indicate that Lactacin B exhibits non-toxic, non-antigenic, and non-hemolytic properties, making it a promising bioactive peptide candidate. Notably, Lactacin B forms strong interactions with GtfB in the active site, with a binding energy of -15.1 kcal/mol and four hydrogen bonds. MD simulations for 100 ns and MMPBSA assays of the complex further support the efficient binding. The fluctuation of RMSD and RMSF is minimal and corresponds to greater stability of the complex. Lactacin B interaction with gtfB mightreduce GtfB's virulence potential, and hinder S. mutans adhesion to oral surfaces, subsequently mitigating biofilm formation and preventing dental caries. However, additional in vitro studies are necessary to validate these findings.

The potential of Streptococcus pyogenes and Escherichia coli bacteriocins in synergistic control of Staphylococcus aureus

Staphylococcus aureus has developed resistance to most conventional antibiotics and is a causative agent of serious infections. Alternative therapies are urgently needed. Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria, including Escherichia coli (E. coli) and Streptococcus pyogenes (S. pyogenes), and represent a potential solution. While several bacteriocins have shown promise, their synergy with bacteriocins from other bacterial species remains largely unexplored. This work used agar diffusion on Muller-Hinton Agar (MHA) with S. aureus as a test bacterium to evaluate E. coli, S. pyogenes and their combined bacteriocins. The bacteriocins of S. pyogenes showed the maximum antimicrobial activity of zone of inhibition (ZOI), 24.93 mm, compared to that of E. coli bacteriocin, which was 19.28 mm, and that of the combined ones at 100% concentration, 22.6 mm. The combined bacteriocins at 50% concentration showed a reduced activity of 18.35 mm. These observations suggest that the bacteriocins produced by S. pyogenes have higher specificity and activity against S. aureus, making them effective therapeutic agents in the fight against multidrug-resistant infections.

In Vitro Insights into Bacteriocin-Mediated Modulation of Chicken Cecal Microbiota

Reducing the use of antibiotics in animal husbandry is essential to limit the spread of resistance. A promising alternative to antibiotics resides in bacteriocins, which are antimicrobial peptides produced by bacteria showing a great diversity in terms of spectrum of activity, structure, and mechanism of action. In this study, the effects of diverse bacteriocins on the composition and metabolic activity of chicken cecal microbiota were examined in vitro, in comparison with antibiotics. Different impacts on microbiota composition were revealed by 16S metabarcoding, with colistin having the most dramatic impact on diversity. Bacteriocins produced by Gram-negative bacteria, microcins J25 and E492, did not significantly influence the microbiota composition. In contrast, bacteriocins from Gram-positive bacteria impacted the abundance of lactic acid bacteria, with nisin Z showing the most impact while pediocin PA-1 (M31L) exhibited a moderate effect at the highest concentration tested. This study emphasizes the potential of bacteriocins as alternatives to antibiotics in poultry to protect from pathogens such as Salmonella, Clostridium, and Enterococcus.

Determination of bacteriocin genes and antimicrobial activity of Lactiplantibacillus plantarum isolated from feta cheese samples

In this study designed to isolate lactic acid bacteria (LAB) with bacteriocin production potential, white cheese samples were collected from different provinces of Turkey and isolation was carried out. A series of experiments were carried out for the main purpose and the actual bacteriocin producers were identified by detecting the genes encoding this bacteriocin. The experiments carried out in this direction were initially carried out with 20 isolates and as a result of various experiments, the number of isolates was reduced to 8 and the study was continued with 8 isolates. In order to determine that the eight isolates identified as a result of a phenotypic and biochemical characterization study were true bacteriocin-producing strains, their antibacterial activity was investigated and then the presence of bacteriocin genes was examined by specific polymerase chain reaction (PCR) using gene-specific primers. As a result, MS16 coded Lactiplantibacillus plantarum OR922652 was found to have strong antibacterial activity against Escherichia coli, Klebsiella pneumonia, Yersinia enterocolitica, Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus; the isolate was susceptible to clinically important antibiotics (ciprofloxacin, gentamicin, penicillin G, ampicillin, chloramphenicol, and vancomycin) and resistant to erythromycin, had no hemolytic activity and possessed plnA and plnD genes encoding bacteriocin production. In conclusion, the MS16 coded L. plantarum isolate has emerged as a promising strain that can be used especially in the health field and in the food industry related to LAB.

The Genetic Determinants of Listeria monocytogenes Resistance to Bacteriocins Produced by Lactic Acid Bacteria

BACKGROUND

Listeria monocytogenes is a Gram-positive bacterium responsible for listeriosis, a serious foodborne disease that can lead to serious health complications. Pregnant women, newborns, the elderly, and patients with weakened immune systems are particularly susceptible to infection. Due to the ability of L. monocytogenes to survive in extreme environmental conditions, such as low temperatures, high salinity, and acidity, this bacterium poses a serious threat to food production plants and is particularly difficult to eliminate from these plants. One of the promising solutions to reduce the presence of this bacterium in food products is bacteriocins as natural control agents. These are substances with antibacterial activity produced by other bacteria, mainly lactic acid bacteria (LAB), which can effectively inhibit the development of pathogens such as L. monocytogenes. The use of bacteriocins in the food industry is beneficial due to their natural origin, specificity of action, and consumer safety. However, the problem of resistance to these substances exists.

RESULTS

This review focuses on the mechanisms of bacteriocin resistance, such as modifications of bacteriocin docking receptors, changes in the structure of the cell wall and membrane, and the occurrence of cross-resistance to different bacteriocins. Genetic factors determining these mechanisms and strategies to cope with the problem of resistance are also presented.

CONCLUSIONS

Research on this issue is crucial for developing effective preventive methods that will enable the safe and long-term use of bacteriocins in food production.

Phenolic Compounds and Bacteriocins: Mechanisms, Interactions, and Applications in Food Preservation and Safety

Beneficial properties of different natural antimicrobials are topics of scientific curiosity for improving safety and extending the shelf life of food commodities. In this regard, phenolic compounds, natural molecules known for their antioxidant, anti-inflammatory, and antimicrobial properties can be right choice. Moreover, bacteriocins, antimicrobial peptides produced by various microorganisms, capable of inhibiting the growth of other bacteria, particularly closely related species can be genuine alternative. Combining phenolic compounds with bacteriocins can enhance antimicrobial effects, extending the shelf-life of food products by combating spoilage and foodborne pathogens. Despite their potential, the chemical interactions between phenolic compounds and bacteriocins, including synergistic and antagonistic effects, are not well understood. Key areas needing further research include the following: the mechanisms of action against different bacterium types, interactions with cell membranes, enzyme activity, and gene expression; the effects of environmental factors like concentration, pH, temperature, and food matrix specificity on their interactions; and methods for incorporating these compounds into food products and packaging materials to improve food safety. Additionally, the safety, toxicity, allergenicity, sensory properties, nutritional value, regulatory approval, and consumer acceptance of using phenolic compounds and bacteriocins in food products require thorough investigation.

Bacterial Proteins and Peptides as Potential Anticancer Agents: A Novel Search for Protein-based Therapeutics

Tumor diseases remain among the world's primary causes of death despite substantial advances in cancer diagnosis and treatment. The adverse chemotherapy problems and sensitivity towards drugs for some cancer types are among the most promising challenges in modern treatment. Finding new anti-cancer agents and drugs is, therefore, essential. A significant class of biologically active substances and prospective medications against cancer is comprised of bacterial proteins and peptides. Among these bacterial peptides, some of them, such as anti-cancer antibiotics and many toxins like diphtheria are widely being used in the treatment of cancer. In contrast, the remaining bacterial peptides are either in clinical trials or under research in vitro studies. This study includes the most recent information on the characteristics and mechanism of action of the bacterial peptides that have anti-cancer activities, some of which are now being employed in cancer therapy while some are still undergoing research.

Antimicrobial Peptides as Broad-Spectrum Therapeutics: Computational Analysis to Identify Universal Physical-Chemical Features Responsible for Multitarget Activity

Antimicrobial peptides (AMPs) hold significant potential as broad-spectrum therapeutics due to their ability to target a variety of different pathogens, including bacteria, fungi, and viruses. However, the rational design of these peptides requires the molecular understanding of properties that enable such broad-spectrum activity. In this study, we present a computational analysis that utilizes machine-learning methods to distinguish peptides with single-target activity from those with activity against multiple pathogens. By optimizing a feature-selection procedure, the most relevant physical-chemical properties, such as dipeptide compositions, solvent accessibility, charge distributions, and optimal hydrophobicity, that differentiate between narrow-spectrum and broad-spectrum peptides are identified. Possible molecular scenarios responsible for the universality of these features are discussed. These findings provide valuable insights into the molecular mechanisms and rational design of multitarget AMPs.

The Bacteriocins Produced by Lactic Acid Bacteria and the Promising Applications in Promoting Gastrointestinal Health

Bacteriocins produced by lactic acid bacteria (LAB) are promising bioactive peptides. Intriguingly, bacteriocins have health benefits to the host and may be applied safely in the food industry as bio-preservatives or as therapeutic interventions preventing intestinal diseases. In recent years, finding a safe alternative approach to conventional treatments to promote gut health is a scientific hotspot. Therefore, this review aimed to give insight into the promising applications of LAB-bacteriocins in preventing intestinal diseases, such as colonic cancer, Helicobacter pylori infections, multidrug-resistant infection-associated colitis, viral gastroenteritis, inflammatory bowel disease, and obesity disorders. Moreover, we highlighted the recent research on bacteriocins promoting gastrointestinal health. The review also provided insights into the proposed mechanisms, challenges and opportunities, trends and prospects. In addition, a SWOT analysis was conducted on the potential applications. Based on properties, biosafety, and health functions of LAB-bacteriocins, we conclude that the future applications of LAB-bacteriocins are promising in promoting gastrointestinal health. Further in vivo trials are needed to confirm these potential effects of LAB-bacteriocins interventions.

A Two Bacteriocinogenic Ligilactobacillus Strain Association Inhibits Growth, Adhesion, and Invasion of Salmonella in a Simulated Chicken Gut Environment

In this study, we aimed to develop a protective probiotic coculture to inhibit the growth of Salmonella enterica serovar Typhimurium in the simulated chicken gut environment. Bacterial strains were isolated from the digestive mucosa of broilers and screened in vitro against Salmonella Typhimurium ATCC 14028. A biocompatibility coculture test was performed, which identified two biocompatible strains, Ligilactobacillus salivarius UO.C109 and Ligilactobacillus saerimneri UO.C121 with high inhibitory activity against Salmonella. The cell-free supernatant (CFS) of the selected isolates exhibited dose-dependent effects, and the inhibitory agents were confirmed to be proteinaceous by enzymatic and thermal treatments. Proteome and genome analyses revealed the presence of known bacteriocins in the CFS of L. salivarius UO.C109, but unknown for L. saerimneri UO.C121. The addition of these selected probiotic candidates altered the bacterial community structure, increased the diversity of the chicken gut microbiota challenged with Salmonella, and significantly reduced the abundances of Enterobacteriaceae, Parasutterlla, Phascolarctobacterium, Enterococcus, and Megamonas. It also modulated microbiome production of short-chain fatty acids (SCFAs) with increased levels of acetic and propionic acids after 12 and 24 h of incubation compared to the microbiome challenged with S. Typhimurium. Furthermore, the selected probiotic candidates reduced the adhesion and invasion of Salmonella to Caco-2 cells by 37-39% and 51%, respectively, after 3 h of incubation, compared to the control. These results suggest that the developed coculture probiotic strains has protective activity and could be an effective strategy to control Salmonella infections in poultry.

Efficient metabolic pathway modification in various strains of lactic acid bacteria using CRISPR/Cas9 system for elevated synthesis of antimicrobial compounds

Lactic acid bacteria (LAB) are known to exhibit various beneficial roles in fermentation, serving as probiotics, and producing a plethora of valuable compounds including antimicrobial activity such as bacteriocin-like inhibitory substance (BLIS) that can be used as biopreservative to improve food safety and quality. However, the yield of BLIS is often limited, which poses a challenge to be commercially competitive with the current preservation practice. Therefore, the present work aimed to establish an optimised two-plasmid CRISPR/Cas9 system to redirect the carbon flux away from lactate towards compounds with antimicrobial activity by disrupting lactate dehydrogenase gene (ldh) on various strains of LAB. The lactic acid-deficient (ldhΔ) strains caused a metabolic shift resulting in increased inhibitory activity against selected foodborne pathogens up to 78 % than the wild-type (WT) strain. The most significant effect was depicted by Enterococcus faecalis-ldh∆ which displayed prominent bactericidal effects against all foodborne pathogens as compared to the WT that showed no antimicrobial activity. The present work provided a framework model for economically important LAB and other beneficial bacteria to synthesise and increase the yield of valuable food and industrial compounds. The present work reported for the first time that the metabolism of selected LAB can be manipulated by modifying ldh to attain metabolites with higher antimicrobial activity.

Addressing the surge of infections by multidrug-resistant Enterobacterales in hematopoietic cell transplantation

Patients undergoing hematopoietic cell transplantation (HCT) have an increased risk of developing severe infections. In recent years, bloodstream infections caused by Gram-negative bacteria have been increasingly reported among HCT recipients, and many of these infections are caused by bacterial strains of the Enterobacterales order. Among these pathogens, particularly concerning are the multidrug-resistant Enterobacterales (MDRE), such as Extended Spectrum β-lactamase-producing Enterobacterales and Carbapenem-resistant Enterobacterales, since infections caused by these pathogens are difficult to treat due to the limited antimicrobial options and are associated with worse transplant outcomes. We summarized the evidence from studies published in PubMed and Scopus on the burden of MDRE infections in HCT recipients, and strategies for the management and prevention of these infections, including strict adherence to recommended infection control practices and multidisciplinary antimicrobial stewardship, the use of probiotics, and fecal microbiota transplantation, are also discussed.

An insight into structure-activity relationships in subclass IIb bacteriocins: Plantaricin EvF

This study reports the structure-activity relationships of a unique subclass IIb bacteriocin, plantaricin EvF, which consists of two peptide chains and possesses potent antimicrobial activity. Because the plantaricin Ev peptide chain lacks an α-helix structure, plantaricin EvF is unable to exert its antimicrobial activity through helix-helix interactions like typical subclass IIb bacteriocins. We have shown by various structural evaluation methods that plantaricin Ev can be stabilized by hydrogen bonding at amino acid residues R3, V12, and R13 to the N-terminal region of plantaricin F. This binding gives plantaricin EvF a special spade-shaped structure that exerts antimicrobial activity. In addition, the root-mean-square deviations (RMSDs) of the amino acid residues Y6, F8, and R13 of plantaricin Ev pre- and post-binding were 1.512, 1.723, and 1.369, respectively, indicating that they underwent large structural changes. The alanine scanning experiments demonstrated the important role of the above key amino acids in maintaining the structural integrity of plantaricin EvF. This study not only reveals the unique structural features of plantaricin EvF, but also provides an insight into the structure-activity relationships of subclass IIb bacteriocins.

Understanding of probiotic origin antimicrobial peptides: a sustainable approach ensuring food safety

The practice of preserving and adding value to food dates back to over 10,000 BCE, when unintentional microbial-driven chemical reactions imparted flavor and extended the shelf life of fermented foods. The process evolved, and with the urbanization of society, significant shifts in dietary habits emerged, accompanied by sporadic food poisoning incidents. The repercussions of the COVID-19 pandemic have intensified the search for antibiotic alternatives owing to the rise in antibiotic-resistant pathogens, emphasizing the exploration of probiotic-origin antimicrobial peptides to alleviate human microbiome collateral damage. Often termed 'molecular knives', these peptides outstand as potent antimicrobials due to their compatibility with innate microflora, amenability to bioengineering, target specificity, versatility and rapidity in molecular level mode of action. This review centres on bacteriocins sourced from lactic acid bacteria found in ethnic fermented foods, accentuating their desirable attributes, technological applications as nanobiotics and potential future applications in the modern context of ensuring food safety.

A comprehensive guide on screening and selection of a suitable AMP against biofilm-forming bacteria

Lately, antimicrobial resistance (AMR) is increasing at an exponential rate making it important to search alternatives to antibiotics in order to combat multi-drug resistant (MDR) bacterial infections. Out of the several antibacterial and antibiofilm strategies being tested, antimicrobial peptides (AMPs) have shown to give better hopes in terms of a long-lasting solution to the problem. To select a desired AMP, it is important to make right use of available tools and databases that aid in identification, classification, and analysis of the physiochemical properties of AMPs. To identify the targets of these AMPs, it becomes crucial to understand their mode-of-action. AMPs can also be used in combination with other antibacterial and antibiofilm agents so as to achieve enhanced efficacy against bacteria and their biofilms. Due to concerns regarding toxicity, stability, and bioavailability, strategizing drug formulation at an early-stage becomes crucial. Although there are few concerns regarding development of bacterial resistance to AMPs, the evolution of resistance to AMPs occurs extremely slowly. This comprehensive review gives a deep insight into the selection of the right AMP, deciding the right target and combination strategy along with the type of formulation needed, and the possible resistance that bacteria can develop to these AMPs.

Bacteriocins sourced from traditional fermented foods for ensuring food safety: the microbial guards

Concerns about food safety have consistently driven the exploration of potent antimicrobials with probiotic origins. Identification of probiotic-derived bacteriocins as robust alternatives to antibiotics has gained traction following the COVID-19 pandemic. Additionally, the global market is witnessing an increasing preference for minimally processed food products free from chemical additives. Another contributing factor to the search for potent antimicrobials is the escalating number of infections caused by antibiotic-resistant bacteria and the need to mitigate the significant damage inflicted on the commensal human microbiota by broad-spectrum antibiotics. As an alternative bio-preservation strategy, there is substantial enthusiasm for the use of bacteriocins or starter cultures producing bacteriocins in preserving a variety of food items. This review specifically focuses on bacteriocins originating from lactic acid bacteria associated with fermented foods and explores their technological applications as nanobiotics. The food-grade antibiotic alternatives, whether utilized independently or in combination with other antimicrobials and administered directly or encapsulated, are anticipated to possess qualities of safety, stability and non-toxicity suitable for application in the food sector. © 2024 Society of Chemical Industry.

A bacteriocin expression platform for targeting pathogenic bacterial species

Bacteriocins are antimicrobial peptides that are naturally produced by many bacteria. They hold great potential in the fight against antibiotic resistant bacteria, including ESKAPE pathogens. Engineered live biotherapeutic products (eLBPs) that secrete bacteriocins can be created to deliver targeted bacteriocin production. Here we develop a modular bacteriocin secretion platform that can be used to express and secrete multiple bacteriocins from non-pathogenic Escherichia coli host strains. As a proof of concept we create Enterocin A (EntA) and Enterocin B (EntB) secreting strains that show strong antimicrobial activity against Enterococcus faecalis and Enterococcus faecium in vitro, and characterise this activity in both solid culture and liquid co-culture. We then develop a Lotka-Volterra model that can be used to capture the interactions of these competitor strains. We show that simultaneous exposure to EntA and EntB can delay Enterococcus growth. Our system has the potential to be used as an eLBP to secrete additional bacteriocins for the targeted killing of pathogenic bacteria.

Evaluation of biodegradability, toxicity and ecotoxicity of organic acid-based deep eutectic solvents

Over the past decade, deep eutectic systems (DES) have become popular, yet their potential toxicity to living organisms is not well understood. This study fills this gap by examining the toxicity, antibacterial activity and biodegradability of p-toluenesulfonic acid monohydrate (PTSA)-based DESs prepared from ammonium or phosphonium salts. Brine shrimp assays revealed varying toxicity levels of PTSA and salts. Allyltriphenylphosphonium bromide showing the longest survival time among all tested salts while PTSA exhibited a significantly longer duration of cell survival compared to other hydrogen bond donors. PTSA and ammonium salts (N,N-diethylethanolammonium chloride and choline chloride) as individual components showed non-toxic behavior for Gram-negative and Gram-positive bacteria while different PTSA-based DESs showed significant inhibition zones. Fish acute ecotoxicity tests indicated moderately toxicity for individual components and DESs, though higher concentrations increased fish mortality, highlighting the need for careful handling and disposal of PTSA-based DESs to the environment. Biodegradability analyses found all tested DESs to be readily biodegradable and it was reported that, DES 3 prepapred form PTSA and choline chloride has the highest biodegradability level. Notably, all tested DESs showed over 60 % biodegradability after 28 days. This groundbreaking study explores PTSA-based DESs, highlighting their biodegradability and potential use as antibacterial agents. Results revealed that PTSA as individual component is much better from toxicity point of view in comparison with PTSA-based DESs for any further industrial applications.

Classification and Multi-Functional Use of Bacteriocins in Health, Biotechnology, and Food Industry

Bacteriocins is the name given to products of the secondary metabolism of many bacterial genera that must display antimicrobial activity. Although there are several bacteriocins described today, it has not been possible to reach a consensus on the method of classification for these biomolecules. In addition, many of them are not yet authorized for therapeutic use against multi-drug-resistant microorganisms due to possible toxic effects. However, recent research has achieved considerable progress in the understanding, classification, and elucidation of their mechanisms of action against microorganisms, which are of medical and biotechnological interest. Therefore, in more current times, protocols are already being conducted for their optimal use, in the hopes of solving multiple health and food conservation problems. This review aims to synthetize the information available nowadays regarding bacteriocins, and their classification, while also providing an insight into the future possibilities of their usage for both the pharmaceutical, food, and biotechnological industry.

Nisin Inhibition of Gram-Negative Bacteria

Aims: This study investigates the activity of the broad-spectrum bacteriocin nisin against a large panel of Gram-negative bacterial isolates, including relevant plant, animal, and human pathogens. The aim is to generate supportive evidence towards the use/inclusion of bacteriocin-based therapeutics and open avenues for their continued development. Methods and Results: Nisin inhibitory activity was screened against a panel of 575 strains of Gram-negative bacteria, encompassing 17 genera. Nisin inhibition was observed in 309 out of 575 strains, challenging the prevailing belief that nisin lacks effectiveness against Gram-negative bacteria. The genera Acinetobacter, Helicobacter, Erwinia, and Xanthomonas exhibited particularly high nisin sensitivity. Conclusions: The findings of this study highlight the promising potential of nisin as a therapeutic agent for several key Gram-negative plant, animal, and human pathogens. These results challenge the prevailing notion that nisin is less effective or ineffective against Gram-negative pathogens when compared to Gram-positive pathogens and support future pursuits of nisin as a complementary therapy to existing antibiotics. Significance and Impact of Study: This research supports further exploration of nisin as a promising therapeutic agent for numerous human, animal, and plant health applications, offering a complementary tool for infection control in the face of multidrug-resistant bacteria.

Investigating lactic acid bacteria genus Lactococcus lactis properties: Antioxidant activity, antibiotic resistance, and antibacterial activity against multidrug-resistant bacteria Staphylococcus aureus

Background

Lactic acid bacteria (LAB) are utilized as a starter culture in the manufacturing of fermented dairy items, as a preservative for various food products, and as a probiotic. In our country, some research has been carried out, even if LAB plays a principal role in food preservation and improves the texture and taste of fermented foods, that is why we tried to evaluate their probiotic effect. The objective of this research was to determine the antibacterial activity of Lactococcus lactis (L. lactis) against Staphylococcus aureus (S. aureus) ATCC 29213, investigate their antioxidant activity, and characterize their sensitivity against 18 antibiotics.

Methods

A total of 23 LAB (L. lactis subsp. cremoris, L. lactis subsp. Lactis diacetylactis, L. lactis subsp. lactis) were isolated from cow's raw milk. The antibacterial activity was performed using two techniques, competition for nutrients and a technique utilizing components nature, using the disk diffusion method. The sensitivity of the studied LAB to different antibiotics was tested on Man rogosa sharp (MRS) agar using commercial antibiotic disks. All strains of LAB were examined for their antioxidant activity. The antioxidant activity of L. lactis was tested by 2,2-diphenyl-1 picrylhydrazyl (DPPH).

Results

The results showed that the MRS medium was more adapted than Muller Hinton Agar (MHA) to investigate the antibacterial activity of L. lactis against S. aureus ATCC 29213. Also, L. lactis exhibited a notable degree of antibacterial activity against S. aureus ATCC 29213. L. Lactis subsp. Lactis displayed higher antibacterial activities, followed by L. lactis ssp. lactis biovar. diacetylactis, and lastly, L. lactis ssp. cremoris against S. aureus ATCC 29213. Lc 26 among all strains of L. lactis showed a high potential antibacterial activity reaching 40 ± 3 mm against S. aureus ATCC 29213. All strains of L. lactis showed a slightly moderate antioxidant activity (10.56 ± 1.28%-26.29 ± 0.05 %). The results of the antibiotic resistance test indicate that all strains of L. lactis were resistant to cefotaxime, sulfamethoxazole-trimethoprim, and streptomycin and were sensitive to Ampicillin, Amoxicillin, Penicillin G, Teicoplanin, Vancomycin, Gentamicin 500, Tetracycline, and Chloramphenicol. These test results indicate that this strain falls within the criteria of not posing any harmful effects on human health. The important antibacterial properties recorded for all L. Lactis strains were derived from the production of antibacterial active metabolites, such as protein, diacetyl, hydrogen peroxide, and lactic acid, together with the fight for nutrients.

Conclusion

This study suggests that the strains of L. lactis could be added as an antibacterial agent against S. aureus ATCC 29213 and can provide an important nutritional property for their antioxidant potential.

Time-resolved cell-to-cell heterogeneity of Listeria innocua after nisin exposure

The use of bacteriocins is a promising approach for addressing the immense threat of food-borne and drug-resistant pathogens. In recent years screening platforms for novel bacteriocins using whole-cell biosensors have been established. During screening cell-to-cell heterogeneity is currently neglected but might play a crucial role in signal development of the whole-cell biosensor after bacteriocin exposure. In this study, we explored the temporal dynamics of the signal heterogeneity of the biosensor Listeria innocua LMG2785/pNZpHin2 Lm after nisin exposure using microfluidic single-cell analysis. The results provided novel and detailed insights into the dynamics of cell-to-cell heterogeneity in L. innocua LMG2785/pNZpHin2 Lm at different nisin concentrations with a high spatio-temporal resolution. Furthermore, the formation of subpopulations during bacteriocin exposure was observed. In-depth single-cell tracking even revealed the regeneration of disrupted cells and recovery of pH homeostasis in rare instances. These findings are highly important for the future design and execution of bacteriocin assays and for the interpretation of fluorescence signal development at the population level after exposure to different concentrations of bacteriocins (here, nisin), as well as for obtaining deeper insights into single-cell persistence strategies to quantify the efficacy and efficiency of novel bacteriocins.

Turbidimetric bioassays: A solution to antimicrobial activity detection in asymptomatic bacteriuria isolates against uropathogenic Escherichia coli

Traditional bacteriocin screening methods often face limitations due to diffusion-related challenges in agar matrices, which can prevent the peptides from reaching their target organism. Turbidimetric techniques offer a solution to these issues, eliminating diffusion-related problems and providing an initial quantification of bacteriocin efficacy in producer organisms. This study involved screening the cell-free supernatant (CFS) from eight uncharacterized asymptomatic bacteriuria (ABU) isolates and Escherichia coli 83972 for antimicrobial activity against clinical uropathogenic E. coli (UPEC) strains using turbidimetric growth methods. ABU isolates exhibiting activity against five or more UPEC strains were further characterized (PUTS 37, PUTS 58, PUTS 59, S-07-4, and SK-106-1). The inhibition of the CFS by proteinase K suggested that the antimicrobial activity was proteinaceous in nature, potentially bacteriocins. The activity of E. coli PUTS 58 and SK-106-1 was enhanced in an artificial urine medium, with both inhibiting all eight UPECs. A putative microcin H47 operon was identified in E. coli SK-106-1, along with a previously identified microcin V and colicin E7 in E. coli PUTS 37 and PUTS 58, respectively. These findings indicate that ABU bacteriocin-producers could serve as viable prophylactics and therapeutics in the face of increasing antibiotic resistance among uropathogens.

The potential of bacteriocins and bacteriophages to control bacterial disease of crops with a focus on Xanthomonas spp

Crop production plays a crucial role in ensuring global food security and maintaining economic stability. The presence of bacterial phytopathogens, particularly Xanthomonas species (a key focus of this review), poses significant threats to crops, leading to substantial economic losses. Current control strategies, such as the use of chemicals and antibiotics, face challenges such as environmental impact and the development of antimicrobial resistance. This review discusses the potential of bacteriocins, bacterial-derived proteinaceous antimicrobials and bacteriophages, viruses that target bacteria as sustainable alternatives for effectively managing Xanthomonas diseases. We focus on the diversity of bacteriocins found within xanthomonads by identifying and predicting the structures of candidate bacteriocin genes from publicly available genome sequences using BAGEL4 and AlphaFold. Harnessing the power of bacteriocins and bacteriophages has great potential as an eco-friendly and sustainable approach for precision control of Xanthomonas diseases in agriculture. However, realising the full potential of these natural antimicrobials requires continued research, field trials and collaboration among scientists, regulators and farmers. This collective effort is crucial to establishing these alternatives as promising substitutes for traditional disease management methods.

Metagenomic nanopore sequencing for exploring the nature of antimicrobial metabolites of Bacillus haynesii

Multidrug-resistant (MDR) pathogens are a rising global health worry that imposes an urgent need for the discovery of novel antibiotics particularly those of natural origin. In this context, we aimed to use the metagenomic nanopore sequence analysis of soil microbiota coupled with the conventional phenotypic screening and genomic analysis for identifying the antimicrobial metabolites produced by promising soil isolate(s). In this study, whole metagenome analysis of the soil sample(s) was performed using MinION™ (Oxford Nanopore Technologies). Aligning and analysis of sequences for probable secondary metabolite gene clusters were extracted and analyzed using the antiSMASH version 2 and DeepBGC. Results of the metagenomic analysis showed the most abundant taxa were Bifidobacterium, Burkholderia, and Nocardiaceae (99.21%, followed by Sphingomonadaceae (82.03%) and B. haynesii (34%). Phenotypic screening of the respective soil samples has resulted in a promising Bacillus isolate that exhibited broad-spectrum antibacterial activities against various MDR pathogens. It was identified using microscopical, cultural, and molecular methods as Bacillus (B.) haynesii isolate MZ922052. The secondary metabolite gene analysis revealed the conservation of seven biosynthetic gene clusters of antibacterial metabolites namely, siderophore lichenicidin VK21-A1/A2 (95% identity), lichenysin (100%), fengycin (53%), terpenes (100%), bacteriocin (100%), Lasso peptide (95%) and bacillibactin (53%). In conclusion, metagenomic nanopore sequence analysis of soil samples coupled with conventional screening helped identify B. haynesii isolate MZ922052 harboring seven biosynthetic gene clusters of promising antimicrobial metabolites. This is the first report for identifying the bacteriocin, lichenysin, and fengycin biosynthetic gene clusters in B. haynesii MZ922052.

In vitro evaluation of the application of an optimized xylanase cocktail for improved monogastric feed digestibility

Xylanases from glycoside hydrolase (GH) families 10 and 11 are common feed additives for broiler chicken diets due to their catalytic activity on the nonstarch polysaccharide xylan. This study investigated the potential of an optimized binary GH10 and GH11 xylanase cocktail to mitigate the antinutritional effects of xylan on the digestibility of locally sourced chicken feed. Immunofluorescence visualization of the activity of the xylanase cocktail on xylan in the yellow corn of the feed showed a substantial collapse in the morphology of cell walls. Secondly, the reduction in the viscosity of the digesta of the feed by the cocktail showed an effective degradation of the soluble fraction of xylan. Analysis of the xylan degradation products from broiler feeds by the xylanase cocktail showed that xylotriose and xylopentaose were the major xylooligosaccharides (XOS) produced. In vitro evaluation of the prebiotic potential of these XOS showed that they improved the growth of the beneficial bacteria Streptococcus thermophilus and Lactobacillus bulgaricus. The antibacterial activity of broths from XOS-supplemented probiotic cultures showed a suppressive effect on the growth of the extraintestinal infectious bacterium Klebsiella pneumoniae. Supplementing the xylanase cocktail in cereal animal feeds attenuated xylan's antinutritional effects by reducing digesta viscosity and releasing entrapped nutrients. Furthermore, the production of prebiotic XOS promoted the growth of beneficial bacteria while inhibiting the growth of pathogens. Based on these effects of the xylanase cocktail on the feed, improved growth performance and better feed conversion can potentially be achieved during poultry rearing.

Bacteriocins: potentials and prospects in health and agrifood systems

Bacteriocins are highly diverse, abundant, and heterogeneous antimicrobial peptides that are ribosomally synthesized by bacteria and archaea. Since their discovery about a century ago, there has been a growing interest in bacteriocin research and applications. This is mainly due to their high antimicrobial properties, narrow or broad spectrum of activity, specificity, low cytotoxicity, and stability. Though initially used to improve food quality and safety, bacteriocins are now globally exploited for innovative applications in human, animal, and food systems as sustainable alternatives to antibiotics. Bacteriocins have the potential to beneficially modulate microbiota, providing viable microbiome-based solutions for the treatment, management, and non-invasive bio-diagnosis of infectious and non-infectious diseases. The use of bacteriocins holds great promise in the modulation of food microbiomes, antimicrobial food packaging, bio-sanitizers and antibiofilm, pre/post-harvest biocontrol, functional food, growth promotion, and sustainable aquaculture. This can undoubtedly improve food security, safety, and quality globally. This review highlights the current trends in bacteriocin research, especially the increasing research outputs and funding, which we believe may proportionate the soaring global interest in bacteriocins. The use of cutting-edge technologies, such as bioengineering, can further enhance the exploitation of bacteriocins for innovative applications in human, animal, and food systems.

Halocin H4 is activated through cleavage by halolysin HlyR4

Halocins are antimicrobial peptides secreted by haloarchaea capable of inhibiting the growth of other haloarchaea or bacteria. Halocin H4 (HalH4) is secreted by the model halophilic archaeon Haloferax mediterranei ATCC 33500. Despite attempts to express halH4 heterologously in Escherichia coli and subsequent careful renaturation procedures commonly employed for haloarchaeal proteins, no active halocin was obtained. However, it was discovered that the antihaloarchaeal activity of this halocin could be activated through cleavage by halolysin R4 (HlyR4), a serine protease also secreted by Hfx. mediterranei ATCC 33500. Replacement of the cysteine at the number 115 amino acid with glycine and deletion of the internal trans-membrane region (15 aa) markedly abolished HalH4's antihaloarchaeal activity. Compared to the N-terminus, the C-terminal amino acid sequence was found to be more crucial for HalH4 to exert its antihaloarchaeal activity. Mass spectrometry analysis revealed that the biologically active antihaloarchaeal peptide produced after hydrolytic cleavage by HlyR4 was the C-terminus of HalH4, suggesting a potential mechanism of action involving pore formation within competitor species' cell membranes. Taken together, this study offers novel insights into the interplay between halocins and secreted proteases, as well as their contribution to antagonistic interaction within haloarchaea.

IMPORTANCE

The antihaloarchaeal function of halocin H4 (HalH4) can be activated by extracellular proteases from haloarchaea, as demonstrated in this study. Notably, we report the first instance of halocin activation through proteolytic cleavage, highlighting its significance in the field. The C-terminus of HalH4 (CTH4) has been identified as the antihaloarchaeal peptide present in hydrolysates generated by HlyR4. The CTH4 exhibited inhibitory activity against a range of haloarchaeal species (Haloarchaeobius spp., Haloarcula spp., Haloferax spp., Halorubellus spp., and Halorubrum spp.), as well as selected bacterial species (Aliifodinibius spp. and Salicola spp.), indicating its broad-spectrum inhibitory potential across domains. The encoding gene of halocin HalH4, halH4, from the model halophilic archaeon Haloferax mediterranei ATCC 33500 can be expressed in Escherichia coli without codon optimization.

Inhibition of Clinical MRSA Isolates by Coagulase Negative Staphylococci of Human Origin

Staphylococcus aureus is frequently highlighted as a priority for novel drug research due to its pathogenicity and ability to develop antibiotic resistance. Coagulase-negative staphylococci (CoNS) are resident flora of the skin and nares. Previous studies have confirmed their ability to kill and prevent colonization by S. aureus through the production of bioactive substances. This study screened a bank of 37 CoNS for their ability to inhibit the growth of methicillin-resistant S. aureus (MRSA). Deferred antagonism assays, growth curves, and antibiofilm testing performed with the cell-free supernatant derived from overnight CoNS cultures indicated antimicrobial and antibiofilm effects against MRSA indicators. Whole genome sequencing and BAGEL4 analysis of 11 CoNS isolates shortlisted for the inhibitory effects they displayed against MRSA led to the identification of two strains possessing complete putative bacteriocin operons. The operons were predicted to encode a nukacin variant and a novel epilancin variant. From this point, strains Staphylococcus hominis C14 and Staphylococcus epidermidis C33 became the focus of the investigation. Through HPLC, a peptide identical to previously characterized nukacin KQU-131 and a novel epilancin variant were isolated from cultures of C14 and C33, respectively. Mass spectrometry confirmed the presence of each peptide in the active fractions. Spot-on-lawn assays demonstrated both bacteriocins could inhibit the growth of an MRSA indicator. The identification of natural products with clinically relevant activity is important in today's climate of escalating antimicrobial resistance and a depleting antibiotic pipeline. These findings also highlight the prospective role CoNS may play as a source of bioactive substances with activity against critical pathogens.

An exploratory in silico analysis of bacteriocin gene clusters in the urobiome

Background: The role of the urobiome in health and disease remains an understudied area compared to the rest of the human microbiome. Enhanced culturing techniques and next-generation sequencing technologies have identified the urobiome as an untapped source of potentially novel antimicrobials. The aim of this study was to screen the urobiome for genes encoding bacteriocin production. Methods: The genomes of 181 bacterial urobiome isolates were screened in silico for the presence of bacteriocin gene clusters using the bacteriocin mining tool BAGEL4 and secondary metabolite screening tool antiSMASH7. Results: From these isolates, an initial 263 areas of interest were identified, manually annotated, and evaluated for potential bacteriocin gene clusters. This resulted in 32 isolates containing 80 potential bacteriocin gene clusters, of which 72% were identified as class II, 13.75% as class III, 8.75% as class I, and 5% as unclassified bacteriocins. Conclusion: Overall, 53 novel variants were discovered, including nisin, gassericin, ubericin, and colicins.

Evaluation of the Effect of Lactobacillus acidophilus ATCC 4356 Bacteriocin against Staphylococcus aureus

Background

Lactobacillus acidophilus is lactic acid bacteria that produce bacteriocins. Bacteriocins are antimicrobial peptides or proteins that exhibit activity against closely related bacteria. The aim of this study was to determine the effect of L. acidophilus ATCC 4356 bacteriocin against Staphylococcus aureus. Material and Methods. We used four different phenotypic methods for antimicrobial activities against two standard strains: methicillin-resistant S. aureus (MRSA) ATCC 33591 and methicillin-susceptible S. aureus (MSSA) ATCC 25923. The methods were (1) agar well diffusion, (2) overlay soft agar, (3) paper disk, and (4) modification of punch hole. The ammonium sulfate method was used to concentrate crude bacteriocin, and ultrafiltration and dialysis tubes were used to remove ammonium sulfate from the bacteriocins. Each method was repeated in triplicate.

Result

L. acidophilus ATCC 4356 showed antimicrobial activity against both MRSA and MSSA standard strains only by the overlay soft agar method and not by the agar well diffusion, punch hole modification, and paper disk methods. No antimicrobial effects were observed in crude bacteriocins concentrated.

Conclusion

The growth inhibition of S. aureus in overlay soft agar method may be due to the production of bacteriocin-like substances. The overlay soft agar method is a qualitative test, so there is a need for further study to optimize the conditions for the production of bacteriocin-like substances in the culture supernatant and precise comparison between the inhibitory activity and pheromone secretion of different strains.

Recent Advances in the Epidemiology of Pathogenic Agents

The COVID-19 pandemic has underscored the pivotal role of epidemiology in studying pathogenic agents [...].

Molecular Dynamic Study on the Structure and Thermal Stability of Mutant Pediocin PA-1 Peptides Engineered with Cysteine Substitutions

Pediocin and analogous bacteriocins, valued for thermal stability, serve as versatile antimicrobials in the food sector. Improving their resilience at high temperatures and deriving derivatives not only benefit food production but also offer broad-spectrum antimicrobial potential in pharmaceuticals, spanning treatments for peptic ulcers, women's health, and novel anticancer agents. The study aims to create mutant peptides capable of establishing a third disulfide bond or enhanced through cysteine substitutions. This involves introducing additional Cys residues into the inherent structure of pediocin PA-1 to facilitate disulfide bond formation. Five mutants (Mut 1-5) were systematically generated with double Cys substitutions and assessed for thermal stability through MD simulations across temperatures (298-394 K). The most robust mutants (Mut 1, Mut 4-5) underwent extended analysis via MD simulations, comparing their structural stability, secondary structure, and surface accessibility to the reference Pediocin PA-1 molecule. This comprehensive assessment aims to understand how Cys substitutions influence disulfide bonds and the overall thermal stability of the mutant peptides. In silico analysis indicated that Mut 1 and Mut 5, along with the reference structure, lose their helical structure and one natural disulfide bond at high temperatures, and may impacting antimicrobial activity. Conversely, Mut 4 retained its helical structure and exhibited thermal stability similar to Pediocin PA-1. Pending further experimental validation, this study implies Mut 4 may have high stability and exceptional resistance to high temperatures, potentially serving as an effective antimicrobial alternative.

Engineering circular bacteriocins: structural and functional effects of α-helix exchanges and disulfide introductions in circularin A

Circular bacteriocins form a distinct group of antimicrobial peptides (AMPs) characterized by their unique head-to-tail ligated circular structure and functional properties. They belong to the ribosomally synthesized and post-translationally modified peptide (RiPP) family. The ribosomal origin of these peptides facilitates rapid diversification through mutations in the precursor genes combined with specific modification enzymes. In this study, we primarily explored the bacteriocin engineering potential of circularin A, a circular bacteriocin produced by Clostridium beijerinckii ATCC 25752. Specifically, we employed strategies involving α-helix replacements and disulfide bond introductions to investigate their effects on both biosynthesis and bioactivity of the bacteriocin. The results show the feasibility of peptide engineering to introduce certain structural properties into circularin A through carefully designed approaches. The introduction of cysteines for potential disulfide bonds resulted in a substantial reduction in bacteriocin biosynthesis and/or bioactivity, indicating the importance of maintaining dynamic flexibility of α-helices in circularin A, while reduction of the potential disulfide in one case increased the activity. The 5 α-helices of circularin A were respectively replaced by corresponding helices from another circular peptide, enterocin AS-48, and modestly active peptides were obtained in a few cases. Overall, this study provides valuable insights into the engineering potential of circular bacteriocins as antimicrobial agents, including their structural and functional restrictions and their suitability as peptide engineering scaffolds. This helps to pave the way for the development of novel antimicrobial peptides with tailored properties based on circular bacteriocins.

Enhanced production of bacteriocin by Bacillus subtilis ZY05

Bacteriocin-producing strains were isolated from the soil of the rice field, screened out using an agar-well diffusion assay against six indicator bacterial strains, and the highest among them was selected for further investigation. The study focuses on how different growing conditions affect bacteriocin production. One-parameter-at-a-time (OPAT) and a central composite design of response surface methodology (RSM) were used to perform the optimization in two steps. In the OPAT trials, bacteriocin synthesis was elevated by 29%, 45%, and 34%, by employing sucrose as a carbon source and changing the NaCl concentration and pH at 7, respectively. To determine the linear, squared, and interaction correlations among the process variables to predict the ideal conditions for production, a four-factor central composite design (CCD) of RSM was used. It was determined that the analysis of variance (ANOVA), which produces a recognized model using RSM, is sufficient to describe bacteriocin production regarding activity (R2 = 0.9606). The ideal conditions for increased production were 1.51% sucrose concentration, 1.59% NaCl concentration, pH 6.35, and 28.66 (about 29) hours of incubation. The value predicted by RSM (4051.55 AU/mL) was approximately two times greater than the value of a non-optimized medium. The experimental value of 4403.85 AU/mL was closer to the expected value. According to the data, increasing bacteriocin activity required employing the ideal sucrose concentration, NaCl concentration, and incubation time. The partially purified bacteriocin was found stable at temperatures between 24 and 50 °C and at pH 5-8. The molecular weight purified bacteriocin was determined to be between 13 and 35 kDa.

The effect of enterocin A/P dipeptide on growth performance, glutathione-peroxidase activity, IgA secretion and jejunal morphology in rabbits after experimental methicillin-resistant Staphylococcus epidermidis P3Tr2a Infection

The increasing frequency of methicillin-resistant (MR) staphylococci in humans and animals need special attention for their difficult treatment and zoonotic character, therefore novel antimicrobial compounds on a natural base against antibiotic-resistant bacteria are requested. Currently, bacteriocins/enterocins present a new promising way to overcome this problem, both in prevention and treatment. Therefore, the preventive and medicinal effect of dipeptide enterocin EntA/P was evaluated against MR Staphylococcus epidermidis SEP3/Tr2a strain in a rabbit model, testing their influence on growth performance, glutathione-peroxidase (GPx) enzyme activity, phagocytic activity (PA), secretory (s)IgA, and jejunal morphometry (JM). Eighty-eight rabbits (aged 35 days, meat line M91, both sexes) were divided into experimental groups S (SEP3/Tr2a strain; 1.0 × 105 CFU/mL; dose 500µL/animal/day for 7 days, between days 14 and 21 to simulate the pathogen attack), E (EntA/P; 50 µL/animal/day, 25,600 AU/mL in two intervals, for preventive effect between days 0 and 14; for medicinal effect between days 28 and 42), E + S (EntA/P + SEP3/Tr2a; preventive effect; SEP3/Tr2a + EntA/P; medicinal effect) and control group (C; without additives). Higher body weight was recorded in all experimental groups (p < 0.001) compared to control data. The negative influence/attack of the SEP3Tra2 strain on the intestinal immunity and environment was reflected as decreased GPx activity, worse JM parameters and higher sIgA concentration in infected rabbits. These results suggest the promising preventive use of EntA/P to improve the immunity and growth of rabbits, as well as its therapeutic potential and protective role against staphylococcal infections in rabbit breeding.

The Networked Interaction between Probiotics and Intestine in Health and Disease: A Promising Success Story

Probiotics are known to promote human health either precautionary in healthy individuals or therapeutically in patients suffering from certain ailments. Although this knowledge was empirical in past tomes, modern science has already verified it and expanded it to new limits. These microorganisms can be found in nature in various foods such as dairy products or in supplements formulated for clinical or preventive use. The current review examines the different mechanisms of action of the probiotic strains and how they interact with the organism of the host. Emphasis is put on the clinical therapeutic use of these beneficial microorganisms in various clinical conditions of the human gastrointestinal tract. Diseases of the gastrointestinal tract and particularly any malfunction and inflammation of the intestines seriously compromise the health of the whole organism. The interaction between the probiotic strains and the host's microbiota can alleviate the clinical signs and symptoms while in some cases, in due course, it can intervene in the underlying pathology. Various safety issues of the use of probiotics are also discussed.

Pseudocin 196, a novel lantibiotic produced by Bifidobacterium pseudocatenulatum elicits antimicrobial activity against clinically relevant pathogens

Bacteriocins are broad or narrow-spectrum antimicrobial compounds that have received significant scientific attention due to their potential to treat infections caused by antibiotic-resistant pathogenic bacteria. The genome of Bifidobacterium pseudocatenulatum MM0196, an antimicrobial-producing, fecal isolate from a healthy pregnant woman, was shown to contain a gene cluster predicted to encode Pseudocin 196, a novel lantibiotic, in addition to proteins involved in its processing, transport and immunity. Following antimicrobial assessment against various indicator strains, protease-sensitive Pseudocin 196 was purified to homogeneity from cell-free supernatant. MALDI TOF mass spectrometry confirmed that the purified antimicrobial compound corresponds to a molecular mass of 2679 Da, which is consistent with that deduced from its genetic origin. Pseudocin 196 is classified as a lantibiotic based on its similarity to lacticin 481, a lanthionine ring-containing lantibiotic produced by Lactococcus lactis. Pseudocin 196, the first reported bacteriocin produced by a B. pseudocatenulatum species of human origin, was shown to inhibit clinically relevant pathogens, such as Clostridium spp. and Streptococcus spp. thereby highlighting the potential application of this strain as a probiotic to treat and prevent bacterial infections.

Medical Device-Associated Healthcare Infections: Sterilization and the Potential of Novel Biological Approaches to Ensure Patient Safety

Healthcare-associated infections caused by multi-drug-resistant pathogens are increasing globally, and current antimicrobial options have limited efficacy against these robust species. The WHO details the critically important bacterial and fungal species that are often associated with medical device HAIs. The effective sterilization of medical devices plays a key role in preventing infectious disease morbidity and mortality. A lack of adherence to protocol and limitations associated with each sterilization modality, however, allows for the incidence of disease. Furthermore, issues relating to carcinogenic emissions from ethylene oxide gas (EtO) have motivated the EPA to propose limiting EtO use or seeking alternative sterilization methods for medical devices. The Food and Drug Administration supports the sterilization of healthcare products using low-temperature VH2O2 as an alternative to EtO. With advances in biomaterial and medical devices and the increasing use of combination products, current sterilization modalities are becoming limited. Novel approaches to disinfection and sterilization of medical devices, biomaterials, and therapeutics are warranted to safeguard public health. Bacteriophages, endolysins, and antimicrobial peptides are considered promising options for the prophylactic and meta-phylactic control of infectious diseases. This timely review discusses the application of these biologics as antimicrobial agents against critically important WHO pathogens, including ESKAPE bacterial species.

Microbisporicin (NAI-107) protects Galleria mellonella from infection with Neisseria gonorrhoeae

IMPORTANCE

We screened 66 bacteriocins to see if they exhibited anti-gonococcal activity. We found 12 bacteriocins with anti-gonococcal effects, and 4 bacteriocins showed higher anti-gonococcal activity. Three bacteriocins, lacticin Z, lacticin Q, and Garvicin KS (ABC), showed in vitro anti-gonococcal activity but no in vivo inhibitory effects against the Neisseria gonorrhoeae (WHO-P) isolate. On the other hand, NAI-107 showed in vivo anti-gonococcal activity. The findings suggest that NAI-107 is a promising alternative to treat gonorrhea infections.

Engineering of Salmonella Phages into Novel Antimicrobial Tailocins

Due to the extensive use of antibiotics, the increase of infections caused by antibiotic-resistant bacteria is now a global health concern. Phages have proven useful for treating bacterial infections and represent a promising alternative or complement to antibiotic treatment. Yet, other alternatives exist, such as bacteria-produced non-replicative protein complexes that can kill their targeted bacteria by puncturing their membrane (Tailocins). To expand the repertoire of Tailocins available, we suggest a new approach that transforms phages into Tailocins. Here, we genetically engineered the virulent Ackermannviridae phage S117, as well as temperate phages Fels-1, -2 and Gifsy-1 and -2, targeting the food pathogen Salmonella, by deleting the portal vertex or major capsid gene using CRISPR-Cas9. We report the production of Tailocin particles from engineered virulent and temperate phages able to kill their native host. Our work represents a steppingstone that taps into the huge diversity of phages and transforms them into versatile puncturing new antimicrobials.

Accumulation of colicin M protein and its biological activity in transgenic lettuce and mizuna plants

Food-borne illnesses caused by pathogenic Escherichia coli strains, especially enterohaemorrhagic E. coli (EHEC), are a serious public health problem, as debilitating disease and even death from such food poisonings have been repeatedly reported. Colicin M (ColM), a non-antibiotic antimicrobial protein produced by some strains of E. coli, has shown promising activity in controlling multiple enteropathogenic strains of E. coli and related pathogens. As contaminated green leafy vegetables are a frequent source of pathogenic E. coli infections, we genetically modified (GM) two edible crops, lettuce (Lactuca sativa L.) and mizuna (Brassica rapa subsp. nipposinica var. laciniata), to stably express the ColM gene and assessed the antibacterial activity of tissue extracts from these plants against selected E. coli strains in vitro. Transgenic plants of these species were developed using Agrobacterium-mediated transformation with a vector containing the ColM-coding gene (cma) under the control of the 35S promoter. Western blot analysis of recombinant ColM protein was performed in selected transgenic plants to confirm cma gene expression and quantify ColM accumulation. Extracts of transgenic plants expressing ColM showed significant activity against two major strains of EHEC (O157:H7 and O104:H4) as well as E. coli strains resistant to beta-lactam- and carbapenem-class antibiotics. Importantly, the antibacterial activity persisted in several subsequent generations of transgenic lettuce and mizuna plants that stably expressed the ColM gene. In addition, our results also show that the antibacterial activity of dried (up to 40°C) biomass of transgenic plants remained stable without a decrease for at least three months.