Biology subjects

Darbon, E.

Publications and source records attributed to Darbon, E..

2 recordsLinked to original sources

bioRxiv2025

Identification of the negamycin split biosynthetic gene cluster in Kitasatospora purpeofusca ATCC21470

Negamycin is a ribosome-targeting antibiotic with activity against Gram-positive and Gram-negative bacteria including ESKAPE pathogens. Furthermore, it promotes premature stop codon readthrough. Its therapeutic potential is limited by low natural production and synthetic complexity. To enable scalable biosynthesis, we identified and characterized its genetic basis in Kitasatospora purpeofusca ATCC 21470. Two distant chromosomal regions, neg1 and neg2, were found to be essential. Deletion of neg1, involved in nitrite provision for N-N bond formation, reduced production to [~]10%, while deletion of neg2, which directs {beta}-lysine generation and scaffold assembly, abolished it completely. Isotope-labeling experiments confirmed nitrite incorporation. Transcriptomic and proteomic analyses further supported the involvement of both regions. The heterologous expression of neg1 along with the neg2 region in Streptomyces albidoflavus reconstituted negamycin biosynthesis, confirming the unusual involvement of two distant gene clusters in the biosynthesis, and provides a foundation for biotechnological production and further development of this promising antibiotic. SIGNIFICANCEThe rapid rise of antimicrobial resistance (AMR), particularly among Gram-negative ESKAPE pathogens, represents one of the most urgent global health threats. Despite this, the discovery and development of new antibiotics have stagnated. Addressing this challenge requires the exploration of natural products with novel mechanisms of action, alongside the development of scalable production strategies. Negamycin has emerged as a compelling candidate in this regard, characterized by an unusual mechanism of action and therapeutic potential extending beyond traditional antibacterial use. However, its development has been constrained by low production yields in the native producer. In this study, we identify and characterize the biosynthetic genes responsible for negamycin production, providing a foundation for pathway engineering, yield optimization, and the rational design of new analogs.

microbiology↗

bioRxiv2021

Marker-free genome engineering in Amycolatopsis using the pSAM2 site-specific recombination system

Actinobacteria belonging to the genus Amycolatopsis are important for antibiotic production and other valuable biotechnological applications such as biodegradation or bioconversion. Despite their industrial importance, tools and methods for the genetic manipulation of Amycolatopsis are less developed than in other actinobacteria such as Streptomyces. Moreover, most of the existing methods do not support convenient marker-free genome engineering. Here, we report the use of the pSAM2 site-specific recombination system for the efficient deletion of marker genes or large DNA regions in Amycolatopsis. For this purpose, we constructed a shuttle vector, replicating in Escherichia coli and Amycolatopsis, expressing the Xis and Int proteins from the Streptomyces integrative and conjugative element pSAM2. These proteins are sufficient for site-specific recombination between the attachment sites attL and attR. We also constructed two plasmids, replicative in E. coli but not in Amycolatopsis, for the integration of the recombination sites attL and attR on each side of a region targeted for deletion. We exemplified the use of these tools in Amycolatopsis mediterranei DSM 40773 by obtaining with high efficiency (>95%) a marker-free deletion of one single gene in the rifamycin biosynthetic gene cluster or of the entire 90-kb cluster. IMPORTANCEThe genus Amycolatopsis is regarded as an important source of diverse specialized metabolites. Members of this genus are used in industry for the production of valuable antibiotics such as rifamycins or vancomycin. Amycolatopsis spp. also present a great interest for biotechnological applications such as biodegradation or bioconversion. Despite their importance, their genetic manipulation was somehow hampered by the lack of efficient tools. Here we report the successful use of the pSAM2 site-specific recombination system to construct unmarked deletion mutants, allowing marker recycling, or to create large deletions in A. mediterranei DSM 40773. The high efficiency of this site-specific recombination system and it possible application to other Amycolatopsis species open new opportunities for marker-free genome engineering in this genus.

molecular biology↗