Discovery of phosphorylated lantibiotics with proimmune activity that regulate the oral microbiome

Natural Antimicrobial Peptides and Their Synthetic Analogues for Effective Oral Microflora Control and Oral Infection Treatment-The Role of Ceragenins in the Development of New Therapeutic Methods

Oral diseases, both acute and chronic, of infectious or non-infectious etiology, represent some of the most serious medical problems in dentistry. Data from the literature increasingly indicate that changes in the oral microbiome, and therefore, the overgrowing of pathological microflora, lead to a variety of oral-localized medical conditions such as caries, gingivitis, and periodontitis. In recent years, compelling research has been devoted to the use of natural antimicrobial peptides as therapeutic agents in the possible treatment of oral diseases. This review focuses on the potential of ceragenins (CSAs), which are lipid analogs of natural antimicrobial peptides, as molecules for the development of new methods for the prevention and treatment of oral diseases. Studies to date indicate that ceragenins, with their spectrum of multidirectional biological activities, including antimicrobial, tissue regeneration-stimulating, anti-inflammatory, and immunomodulatory properties, are strong candidates for further development of oral formulations. However, many of the beneficial properties of ceragenins require confirmation in experimental conditions reproducing the oral environment to fully determine their application potential. Their transition to practical use also requires more advanced testing of these molecules in clinical trials, which have only been conducted in limited numbers to date.

Exploring nature's battlefield: organismic interactions in the discovery of bioactive natural products

Covering: up to March 2024.Microbial natural products have historically been a cornerstone for the discovery of therapeutic agents. Advanced (meta)genome sequencing technologies have revealed that microbes harbor far greater biosynthetic capabilities than previously anticipated. However, despite the application of CRISPR/Cas-based gene editing and high-throughput technologies to activate silent biosynthetic gene clusters, the rapid identification of new natural products has not led to a proportional increase in the discovery rate of lead compounds or drugs. A crucial issue in this gap may be insufficient knowledge about the inherent biological and physiological functions of microbial natural products. Addressing this gap necessitates recognizing that the generation of functional natural products is deeply rooted in the interactions between the producing microbes and other (micro)organisms within their ecological contexts, an understanding that is essential for harnessing their potential therapeutic benefits. In this review, we highlight the discovery of functional microbial natural products from diverse niches, including those associated with humans, nematodes, insects, fungi, protozoa, plants, and marine animals. Many of these findings result from an organismic-interaction-guided strategy using multi-omic approaches. The current importance of this topic lies in its potential to advance drug discovery in an era marked by increasing antimicrobial resistance.

Bibacillin 1: a two-component lantibiotic from Bacillus thuringiensis

Here we describe bibacillin 1 - a two-component lantibiotic from Bacillus thuringiensis. The peptides that comprise bibacillin 1 are modified by a class II lanthipeptide synthetase Bib1M producing two peptides with non-overlapping ring patterns that are reminiscent of cerecidin and the short component of the enterococcal cytolysin (CylLS''), a virulence factor associated with human disease. Stereochemical analysis demonstrated that each component contains ll-methyllanthionine and dl-lanthionine. The mature bibacillin 1 peptides showed cooperative bactericidal activity against Gram-positive bacteria, including members of the ESKAPE pathogens, and weak hemolytic activity. Optimal ratio studies suggest that bibacillin 1 works best when the components are present in a 1 : 1 ratio, but near optimal activity was observed at ratios strongly favouring one component over the other, suggesting that the two peptides may have different but complementary targets. Mechanism of action studies suggest a lipid II-independent killing action distinguishing bibacillin 1 from two other two-component lantibiotics haloduracin and lacticin 3147. One of the two components of bibacillin 1 showed cross reactivity with the cytolysin regulatory system. These result support the involvement of bibacillin 1 in quorum sensing and raise questions about the impact of CylLS''-like natural products on lanthipeptide expression in diverse bacterial communities.

Bibacillin 1: A two-component lantibiotic from Bacillus thuringiensis

Here we describe bibacillin 1 - a two-component lantibiotic from Bacillus thuringiensis. The peptides that comprise bibacillin 1 are modified by a class II lanthipeptide synthetase Bib1M producing two peptides with non-overlapping ring patterns that are reminiscent of cerecidin and the short component of the enterococcal cytolysin (CylLS"), a virulence factor associated with human disease. Stereochemical analysis demonstrated that each component contains LL-methyllanthionine and DL-lanthionine. The mature bibacillin 1 peptides showed cooperative bactericidal activity against Gram-positive bacteria, including members of ESKAPE pathogens, and weak hemolytic activity. Optimal ratio studies suggest that bibacillin 1 works best when the components are present in a 1:1 ratio, but near optimal activity was observed at ratios strongly favouring one component over the other, suggesting that the two peptides may have different but complementary targets. Mechanism of action studies suggest a lipid II-independent killing action distinguishing bibacillin 1 from two other two-component lantibiotics haloduracin and lacticin 3147. One of the two components of bibacillin 1 showed cross reactivity with the cytolysin regulatory system. These result support the involvement of bibacillin 1 in quorum sensing and raise questions about the impact of CylLS"-like natural products on lanthipeptide expression in diverse bacterial communities.

Characterization of a LanC-free pathway for the formation of an ll-MeLan residue and an alloAviMeCys residue in the newly identified class V lanthipeptide triantimycins

The thioether-connected bis-amino acid lanthionine (Lan) residues are class-defining residues of lanthipeptides. Typically, the cyclization step of lanthionine formation, which relies on the addition of a cysteine to an unsaturated dehydroamino acid, is directed either by a standalone cyclase LanC (class I) or by a cyclase domain (class II-IV). However, the pathways of characterized class V members often lack a known cyclase (domain), raising a question on the mechanism by which their multi-macrocycle systems are formed. Herein, we report a new RiPP gene cluster in Streptomyces TN 58, where it encodes the biosynthesis of 3 distinct class V lanthipeptides-termed triantimycins (TAMs). TAM A1∼A3 share an N-terminal ll-MeLan residue, and only TAM A1 contains an additional internal ll-Lan residue. TAM A1 also has a C-terminal (2S, 3R)-S-((Z)-2-aminovinyl)-3-methyl-d-cysteine (alloAviMeCys) residue, which is distinct from the previously reported (2S, 3S)-AviMeCys residue in other RiPPs. Gene deletion, heterologous coexpression, and structural elucidation demonstrated that the cyclization for an ll-MeLan formation occurs spontaneously and is independent of any known lanthionine cyclase. This study provides a new paradigm for lanthionine formation and facilitates genome mining and engineering efforts on RiPPs containing (Me)Lan and (allo)Avi(Me)Cys residues.

Activity of Gut-Derived Nisin-like Lantibiotics against Human Gut Pathogens and Commensals

Recent advances in sequencing techniques unveiled the vast potential of ribosomally synthesized and post-translationally modified peptides (RiPPs) encoded in microbiomes. Class I lantibiotics such as nisin A, widely used as a food preservative, have been investigated for their efficacy in killing pathogens. However, the impact of nisin and nisin-like class I lantibiotics on commensal bacteria residing in the human gut remains unclear. Here, we report six gut-derived class I lantibiotics that are close homologues of nisin, four of which are novel. We applied an improved lantibiotic expression platform to produce and purify these lantibiotics for antimicrobial assays. We determined their minimal inhibitory concentration (MIC) against both Gram-positive human pathogens and gut commensals and profiled the lantibiotic resistance genes in these pathogens and commensals. Structure-activity relationship (SAR) studies with analogs revealed key regions and residues that impact their antimicrobial properties. Our characterization and SAR studies of nisin-like lantibiotics against both pathogens and human gut commensals could shed light on the future development of lantibiotic-based therapeutics and food preservatives.

Role of probiotics in managing various human diseases, from oral pathology to cancer and gastrointestinal diseases

The imbalance of microbial composition and diversity in favor of pathogenic microorganisms combined with a loss of beneficial gut microbiota taxa results from factors such as age, diet, antimicrobial administration for different infections, other underlying medical conditions, etc. Probiotics are known for their capacity to improve health by stimulating the indigenous gut microbiota, enhancing host immunity resistance to infection, helping digestion, and carrying out various other functions. Concurrently, the metabolites produced by these microorganisms, termed postbiotics, which include compounds like bacteriocins, lactic acid, and hydrogen peroxide, contribute to inhibiting a wide range of pathogenic bacteria. This review presents an update on using probiotics in managing and treating various human diseases, including complications that may emerge during or after a COVID-19 infection.