Pham, N. Q. | bioRxiv Science

bioRxiv2025

β-nicotinamide mononucleotide production in Vibrio natriegens: a preliminary study

BackgroundNicotinamide mononucleotide (NMN), is a promising nutraceutical attracting much attention for its pharmacological and anti-aging efficacies. However, NMN-containing commercial products are very high-priced due to the lack of efficient and facile methods for industrial-scale production. To date, various metabolic engineering strategies have been successfully applied to produce NMN in Escherichia coli. Recently, Vibrio natriegens has become a promising host in the bioindustry thanks to its rapid growth and capabilities of broad substrate utilization. This study aims to evaluate the NMN biosynthesis capability of V. natriegens. MethodsFirstly, a mutant V. natriegens strain ({Delta}dns::araC-T7RNAP-KanR{Delta} pncC::FtnadE-SmR{Delta} nadR) was generated via multiplex genome editing by natural transformation (MuGENT). Nampt genes encoding nicotinamide phosphoribosyltransferase from Chitinophaga pinensis, Sphingopyxis sp. C-1, Haemophilus ducreyi, and Vibrio phage KVP40 were codon-optimized and cloned into pACYCDuet-1 under the control of T7 promoter. The recombinant plasmids were electroporated into the mutant strain. The expression of recombinant NAMPTs in V. natriegens was evaluated by SDS-PAGE analysis and the intracellular NMN concentrations were quantified by HPLC. ResultsAfter two rounds of MuGENT, V. natriegens V54-33 strain ({Delta}dns::araC-T7RNAP-KanR{Delta} pncC::FtnadE-SmR{Delta} nadR) was successfully generated. SDS-PAGE analysis demonstrated that all NAMPTs were strongly expressed in the V54-33 strain. HPLC analysis revealed that the highest intracellular NMN concentration was obtained with NAMPT from Chitinophaga pinensis (44.5 M), followed by NAMPT from Vibrio phage KVP40 (23.3 M). ConclusionThis study demonstrated the feasibility of NMN biosynthesis in V. natriegens.

bioengineering↗

bioRxiv2025

Tracing the evolution and genomic dynamics of mating-type loci in Cryptococcus pathogens and closely related species

Sexual reproduction in basidiomycete fungi is governed by MAT loci (P/R and HD), which exhibit remarkable evolutionary plasticity, characterized by expansions, rearrangements, and gene losses often associated with mating system transitions. The sister genera Cryptococcus and Kwoniella provide a powerful framework for studying MAT loci evolution owing to their diverse reproductive strategies and distinct architectures, spanning bipolar and tetrapolar systems with either linked or unlinked MAT loci. Building on recent comparative genomic analyses, we generated additional chromosome-level assemblies, uncovering distinct trajectories shaping MAT loci organization. Contrasting with the small-scale expansions and gene acquisitions observed in Kwoniella, our analyses revealed independent expansions of the P/R locus in tetrapolar Cryptococcus, possibly driven by pheromone gene duplications. Notably, these expansions coincided with a pronounced GC-content reduction best explained by reduced GC-biased gene conversion following recombination suppression, rather than relaxed codon usage selection. Diverse modes of MAT locus linkage were also identified, including three previously unrecognized transitions: one resulting in a pseudobipolar arrangement and two leading to bipolarity. All three transitions involved translocations. In the pseudobipolar configuration, the P/R and HD loci remained on the same chromosome but genetically unlinked, whereas the bipolar transitions additionally featured rearrangements that fused the two loci into a nonrecombining region. Mating assays confirmed a sexual cycle in C. decagattii, demonstrating its ability to undergo mating and sporulation. Progeny analysis in K. mangrovensis revealed substantial ploidy variation and aneuploidy, likely stemming from haploid-diploid mating, yet evidence of recombination and loss of heterozygosity indicates that meiotic exchange occurs despite irregular chromosome segregation. Our findings underscore the importance of continued diversity sampling and provide further evidence for convergent evolution of fused MAT loci in basidiomycetes, offering new insights into the genetic and chromosomal changes driving reproductive transitions.

genetics↗