RESUMEN
Phosphorus (P) deficiency is a predominant constraint on plant growth in acidified soils, largely due to the sequestration of P by toxic aluminum (Al) compounds. Indigenous phosphorus-solubilizing bacteria (PSBs) capable of mobilizing Al-P in these soils hold significant promise. A novel Al-P-solubilizing strain, Al-P Nguyenibacter sp. L1, was isolated from the rhizosphere soil of healthy Lespedeza bicolor plants indigenous to acidic terrains. However, our understanding of the genomic landscape of bacterial species within the genus Nguyenibacter remains in its infancy. To further explore its biotechnological potentialities, we sequenced the complete genome of this strain, employing an amalgamation of Oxford Nanopore ONT and Illumina sequencing platforms. The resultant genomic sequence of Nguyenibacter sp. L1 manifests as a singular, circular chromosome encompassing 4,294,433 nucleotides and displaying a GC content of 66.73%. The genome was found to host 3,820 protein-coding sequences, 12 rRNAs, and 55 tRNAs. Intriguingly, annotations derived from the eggNOG and KEGG databases indicate the presence of genes affiliated with phosphorus solubilization and nitrogen fixation, including iscU, glnA, and gltB/D associated with nitrogen fixation, and pqqBC associated with inorganic phosphate dissolution. Several bioactive secondary metabolite genes in the genome, including pqqCDE, phytoene synthase and squalene synthase predicted by antiSMASH. Moreover, we uncovered a complete metabolic pathway for ammonia, suggesting an ammonia-affinity property inherent to Nguyenibacter sp. L1. This study verifies the nitrogen-fixing and phosphate-dissolving abilities of Nguyenibacter sp. L1 at the molecular level through genetic screening and analysis. The insights gleaned from this study offer strategic guidance for future strain enhancement and establish a strong foundation for the potential incorporation of this bacterium into agricultural practices.
RESUMEN
OBJECTIVES: To induce natural genetic competence in Bacillus amyloliquefaciens isolates through overexpression of the master regulator, ComK, from B. subtilis (ComK Bsu ). RESULTS: Plasmid pUBXC carrying the xylose-inducible comK expression cassette was constructed using plasmid pUB110 as a backbone. Plasmid pUBXC could be transferred from B. subtilis to B. amyloliquefaciens through plasmid pLS20-mediated biparental conjugation. After being induced by xylose, four B. amyloliquefaciens strains harbouring plasmid pUBXC developed genetic competence. Under optimal conditions, the transformation efficiencies of plasmid DNA ranged from 129 ± 20.6 to 1.7 ± 0.1 × 105 cfu (colony-forming units) per µg DNA, and the transformation efficiencies of PCR-assembled deletion constructs ranged from 3.2 ± 0.76 to 3.5 ± 0.42 × 104 cfu per µg DNA in the four tested strains. CONCLUSION: Artificial induction of genetic competence through overexpressing ComK Bsu in B. amyloliquefaciens completed the tasks of replicative plasmid delivery and gene knockout via direct transformation of PCR-generated deletion cassettes.