Biology subjects

Jaffal, H.

Publications and source records attributed to Jaffal, H..

4 recordsLinked to original sources

bioRxiv2026

Effect of gene cluster relocation to the central chromosomal compartment on its expression in Streptomyces

Streptomyces bacteria are renowned for their intricate life cycle and prolific production of specialized metabolites, including antibiotics. Their linear chromosome is spatially compartmentalized: the central region contains highly conserved and expressed genes, while the terminal regions harbor less conserved, poorly expressed sequences, often rich in specialized metabolite biosynthetic gene clusters. To investigate the relationship between genome architecture and gene expression, we relocated the congocidine antibiotic biosynthetic gene cluster (CGC) from its native terminal position to the central compartment in Streptomyces ambofaciens. This relocation enhanced CGC transcription compared to its original terminal location, both in antisense orientation during exponential growth and in sense orientation after metabolic differentiation, resulting in 50% increase in congocidine production. At the 3D-level, transcription-induced domains formed at both the relocated and native CGC sites, creating sharp boundaries at a larger scale. Notably, the formation of such a boundary in the central compartment during the early stationary phase did not disrupt interarm contacts or affect neighboring gene expression. These results indicate that relocating a terminal cluster to the central chromosomal compartment provides a more favorable environment for transcription without altering chromosome compaction in the stationary phase, offering a promising strategy to enhance antibiotic production in the native host. Key points- Central relocation of a gene cluster enhanced its transcription while preserving chromosome compaction. - A transcription-induced domain formed at the new locus without altering neighboring gene expression. - This strategy increased antibiotic yield by 50% in the native host.

microbiology↗

bioRxiv2025

A new-engineered integrative tool to target the terminal compartment of the Streptomyces chromosome

Phages are a valuable resource for the genetic engineering of Streptomyces antibiotic-producing bacteria. Indeed, a few integrative vectors based on phage integrase are available to insert transgene at specific genomic loci. Chromosome conformation captures previously demonstrated that the Streptomyces linear chromosome is organized in two spatial compartments: The central compartment encompassing most conserved and highly expressed genes in exponential phase, and the terminal compartments enriched in poorly conserved sequences including specialized metabolite biosynthetic gene clusters. This study introduces a new integrative tool based a recently described phage, Samy, which specifically targets the terminal compartment of its native host chromosome. Samy is related to PhiC31 phage and, like this latter, encodes a serine integrase. Whereas PhiC31 targets a site generally located near the origin of replication, the Samy integration site is one of the farthest known attB sites from it. We demonstrated that the Samy integrase efficiently mediates the specific integration of a non-replicating plasmid in six Streptomyces strains from distinct clades. Bioinformatic analyses revealed that the Samy attB site is rather conserved, and located in the terminal compartment of most Streptomyces chromosomes. Unusually for a serine integrase, Samy-based integration system exhibits slight excision. The Samy orthogonal site-specific recombination system extends the range of genetic tools available for engineering the Streptomyces chromosome by broadening the range of targeted locations, especially within the terminal spatial compartment. Key points- Samy-based integrative vectors are new tools for engineering Streptomyces strains. - They are among the few targeting the terminal compartment of the chromosome. - Their integration is farthest from the replication origin in most strains compared to other vectors.

bioengineering↗

bioRxiv2023

Phage-mediated dispersal of multicellular bacteria

Streptomyces are renowned for their prolific production of specialized metabolites with applications in medicine and agriculture. These multicellular bacteria present a sophisticated developmental cycle, and play a key role in soil ecology. Little is known about Streptomyces-phage interactions and the impact of phages on Streptomyces physiology. In this study, we investigated the conditions governing the expression and production of Samy, a prophage found in Streptomyces ambofaciens ATCC 23877. This siphoprophage is produced simultaneously with the activation of other mobile genetic elements. We show that Samy production increases bacterial dispersal under in vitro stress conditions. Altogether, we unveiled a new property of a bacteriophage infection that it is closely linked to the multicellular community life of Streptomyces bacteria. Graphical summary O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/549817v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@126b3fcorg.highwire.dtl.DTLVardef@1f26808org.highwire.dtl.DTLVardef@18bfdcforg.highwire.dtl.DTLVardef@1c44be3_HPS_FORMAT_FIGEXP M_FIG C_FIG IMPORTANCEStreptomyces are multicellular bacteria producing valuable metabolites, including antibiotics, with applications in medicine and agriculture. In this study, we characterized a novel temperate phage, named Samy, and its impact on bacteria physiology. Remarkably, the presence and production of Samy increases bacterial dispersal under in vitro stress conditions. This constitutes an emerging property associated with bacteriophage infection that might enhance the spread of the species. Our study reveals a new aspect of bacteriophage infection in the context of multicellular aggregate dynamics.

microbiology↗

bioRxiv2022

Platelet phosphatidylserine is the critical mediator of thrombosis in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a severe immune-mediated prothrombotic disorder caused by antibodies reactive to complexes of platelet factor 4 and heparin. Platelets (PLTs) and their interaction with different immune cells contribute to prothrombotic conditions in HIT. However, the exact mechanisms and the role of different PLT subpopulations to this prothrombotic enviroment remain poorly understood. In this study, we observed that HIT patient antibodies (Abs) induce relevant changes in PLT phenotype, with the key features being increased P-Selectin expression and procoagulant phosphatidylserine (PS) externalization. Formation of procoagulant PLTs was dependent on engagement of PLT Fc-gamma-RIIA by HIT Abs and resulted in significant increase of thrombin generation on the PLT surface. Using an ex vivo thrombosis model and multi-parameter assessment of thrombus formation, we observed that HIT Ab-induced procoagulant PLTs propagated formation of large PLT aggregates, leukocyte recruitment and most importantly, fibrin network generation. These prothrombotic conditions were prevented via the upregulation of PLTs intracellular cAMP with Iloprost, a clinically approved prostacyclin analogue. Additionally, the functional relevance of high P-Selectin and PS levels on procoagulant PLTs was dissected. While inhibition of P-Selectin did not affect thrombus formation, the specific blockade of PS with Lactadherin prevented HIT Ab-mediated thrombin generation and most importantly procoagulant PLT-mediated thrombus formation ex vivo. Taken together, our findings indicate that procoagulant PLTs are critical mediators of prothrombotic conditions in HIT. Upregulation of cAMP with Iloprost or PS targeting specifc therapeutics could be a promising approach to prevent thromboembolic events in HIT patients. Key points- HIT immune complexes drive procoagulant platelet formation - Phosphatidylserine blockade prevents HIT antibody-induced thrombus formation

immunology↗