Gene expression regulation by modulating Hfq expression in coordination with tailor-made sRNA-based knockdown in Escherichia coli.

The tailor-made synthetic sRNA-based gene expression knockdown system has demonstrated its efficacy in achieving pathway balancing in microbes, facilitating precise target gene repression and fine-tuned control of gene expression. This system operates under a competitive mode of gene regulation, wherein the tailor-made synthetic sRNA shares the intrinsic intracellular Hfq protein with other RNAs. The limited intracellular Hfq amount has the potential to become a constraining factor in the post-transcription regulation of sRNAs. To enhance the efficiency of the tailor-made sRNA gene expression regulation platform, we introduced an Hfq expression level modulation-coordinated sRNA-based gene knockdown system. This system comprises tailor-made sRNA expression cassettes that produce varying Hfq expression levels using different strength promoters. Modulating the expression levels of Hfq significantly improved the repressing capacity of sRNA, as evidenced by evaluations with four fluorescence proteins. In order to validate the practical application of this system, we applied the Hfq-modulated sRNA-based gene knockdown cassette to Escherichia coli strains producing 5-aminolevulinic acid and L-tyrosine. Diversifying the expression levels of metabolic enzymes through this cassette resulted in substantial increases of 74.6% in 5-aminolevulinic acid and 144% in L-tyrosine production. Tailor-made synthetic sRNA-based gene expression knockdown system, coupled with Hfq copy modulation, exhibits potential for optimizing metabolic fluxes through biosynthetic pathways, thereby enhancing the production yields of bioproducts.

Subnasale flap for correction of columellar deformity.

BACKGROUND: Columellar defects or deformities are challenging problems to correct. Many different techniques have been described, yet none are ideal, especially for the purpose of aesthetic improvement. METHODS: Local flaps are designed from the subnasale region extending into the nasal floor. It is a one-stage procedure that transfers well-matched skin to the columella. Flaps are rotated medially to improve various types of columellar deformities. The flap was used in 20 cases for defective, narrow, and deviated columella. RESULTS: Results in all of the cases were satisfactory, with minimal complications. CONCLUSIONS: The procedure is relatively simple, and primary closure of the donor site is possible without causing external deformity. The subnasale flap can be fashioned without a visible donor-site scar. It is indicated for partial to total reconstruction of columellar defects, aesthetic improvement of narrow columella, and correction of deviated columella.