Heterologous Production and Structure Determination of a New Lanthipeptide Sinosporapeptin Using a Cryptic Gene Cluster in an Actinobacterium Sinosporangium siamense

BGC heteroexpression strategy for production of novel microbial secondary metabolites

Biosynthetic gene clusters (BGCs) in microbial genomes play a crucial role in the biosynthesis of diverse secondary metabolites (SMs) with pharmaceutical potential. However, most BGCs remain silent under conventional conditions, resulting in the frequently repeated discovery of known SMs. Fortunately, in the past two decades, the heterologous expression of BGCs in genetically tractable hosts has emerged as a powerful strategy to awaken microbial metabolic pathways for making novel microbial SMs. In this review, we comprehensively delineated the development and application of this strategy, highlighting various BGC cloning and assembly techniques and their technical characteristics. We also summarized 519 novel SMs from BGC hetero-expression-derived strains and described their occurrence, bioactivity, mode of action, and biosynthetic logic. Lastly, current challenges and future perspectives for developing more efficient BGC hetero-expression strategies were discussed in this review.

Isolation and structure determination of a new antibacterial lanthipeptide derived from the marine derived bacterium Lysinibacillus sp.CTST325

Marine resources are attractive for screening new useful bacteria. From a marine sediment sample, we performed isolation and screening of bacterial strains in search of new bioactive compounds. HPLC and ESI-MS analysis indicated that the new bacterium, Lysinibacillus sp. CTST325 (NBRC 116944), produced a new peptidic compound, lysinibacin. Genome sequence analysis of Lysinibacillus sp. CTST325 indicated the presence of several biosynthetic gene clusters for secondary metabolites, including lanthipeptides. The structure determination of lysinibacin was performed using CID-MS and NMR spectral data. As a result, lysinibacin was identified as a new class III lanthipeptide, containing N-dimethylated Tyr at the N-terminus and the unusual amino acid labionin at the C-terminus. The biosynthetic gene cluster of lysinibacin was identified from the genome data of the strain CTST325, based on the structure of lysinibacin. Lysinibacin showed antibacterial activity against Gram-positive bacteria.

Heterologous biosynthesis of myxobacterial lanthipeptides melittapeptins

The myxobacteria are an attractive bioresource for bioactive compounds since the large size genome contains many biosynthetic gene clusters of secondary metabolites. The genome of the myxobacterium Melittangium boletus contains three biosynthetic gene clusters for lanthipeptide production. One of the gene clusters includes genes coding lanthipeptide precursor (melA), class II lanthipeptide synthetase (melM), and transporter (melT). The amino acid sequence of melA indicated similarity with that of known lanthipeptides mersacidin and lichenicidin A1 by the alignment. To perform heterologous production of new lanthipeptides, the expression vector containing the essential genes (melA and melM) was constructed by utilizing codon-optimized synthetic genes. The co-expression of two genes in the host bacterial cells of Escherichia coli BL21 (DE3) afforded new lanthipeptides named melittapeptins A-C. The structures of melittapeptins A-C including lanthionine/methyllanthionine bridge pattern were proposed based on protease digestion and MS/MS experiments. The native strain of M. boletus did not produce melittapeptins A-C, so heterologous production using the biosynthetic gene cluster was effective in obtaining the lanthipeptides. Melittapeptins A-C showed specific and potent antibacterial activity to the Gram-positive bacterium Micrococcus luteus. To the best of our knowledge, this is the first report of antibacterial lanthipeptides derived from myxobacterial origin. KEY POINTS: • New lanthipeptides melittapeptins were heterologously produced in Escherichia coli. • Melittapeptins showed specific antibacterial activity against Micrococcus luteus. • Melittapeptins were the first antibacterial lanthipeptides of myxobacterial origin.

Antimicrobial Peptides Derived from Bacteria: Classification, Sources, and Mechanism of Action against Multidrug-Resistant Bacteria

Antimicrobial peptides (AMPs) are short, usually cationic peptides with an amphiphilic structure, which allows them to easily bind and interact with the cellular membranes of viruses, bacteria, fungi, and other pathogens. Bacterial AMPs, or bacteriocins, can be produced from Gram-negative and Gram-positive bacteria via ribosomal synthesis to eliminate competing organisms. Bacterial AMPs are vital in addressing the increasing antibiotic resistance of various pathogens, potentially serving as an alternative to ineffective antibiotics. Bacteriocins have a narrow spectrum of action, making them highly specific antibacterial compounds that target particular bacterial pathogens. This review covers the two main groups of bacteriocins produced by Gram-negative and Gram-positive bacteria, their modes of action, classification, sources of positive effects they can play on the human body, and their limitations and future perspectives as an alternative to antibiotics.

Facile Method for Determining Lanthipeptide Stereochemistry

Lanthipeptides make up a large group of natural products that belong to the ribosomally synthesized and post-translationally modified peptides (RiPPs). Lanthipeptides contain lanthionine and methyllanthionine bis-amino acids that have varying stereochemistry. The stereochemistry of new lanthipeptides is often not determined because current methods require equipment that is not standard in most laboratories. In this study, we developed a facile, efficient, and user-friendly method for detecting lanthipeptide stereochemistry, utilizing advanced Marfey's analysis with detection by liquid chromatography coupled with mass spectrometry (LC-MS). Under optimized conditions, 0.05 mg of peptide is sufficient to characterize the stereochemistry of five (methyl)lanthionines of different stereochemistry using a simple liquid chromatography setup, which is a much lower detection limit than current methods. In addition, we describe methods to readily access standards of the three different methyllanthionine stereoisomers and two different lanthionine stereoisomers that have been reported in known lanthipeptides. The developed workflow uses a commonly used nonchiral column system and offers a scalable platform to assist antimicrobial discovery. We illustrate its utility with an example of a lanthipeptide discovered by genome mining.