Objective:To identify and characterize one Yokenella regensburgei strain(designated as CXLZQ123) isolated from a case of perionychial abscess. Methods:Strain CXLZQ123 was isolated from a patient with periungual abscess at the Dermatology Department of San County Central Hospital in June 2, 2023. The strain was initially identified through morphological and biochemical tests, followed by mass spectrometry identification, 16S rRNA sequencing and whole-genome sequencing. MEGA 11.0 was used to compare and analyze the strain′s genetic relationship with relevant species in GenBank, and a phylogenetic tree was constructed based on genetic distance to analyze its genetic evolution. Meanwhile, the average nucleotide identity between its genome and similar strains were compared.Results:The strain was identified as a Gram-negative rod. MicroScan WalkAway biochemical tests indicated that the strain was either Yokenella regensburgei (91.47%) or Hafnia alvei (8.53%). MALDI-TOF mass spectrometry confirmed it as Yokenella regensburgei. Based on 16S rRNA gene sequence analysis, the strain showed the highest similarity(99.37%) to CIP 105435 (sequence number NR_104934.1). The 16S rRNA gene sequence of the isolated strain Yokenella regensburgei was submitted to the National Center for Biotechnology Information (NCBI) with the GenBank sequence number of OR230248.1. The whole-genome of CXLZQ123 were sequenced and uploaded (NCBI, SRA sequence number: SRR26510420). The average nucleotide identity between CXLZQ123 and Yokenella regensburgei strains W13 and UU2206353 were 98.82% and 99.04%, respectively. Conclusions:Through morphological observation, biochemical identification, mass spectrometry identification, 16S rRNA and whole-genome sequencing, this pathogenic strain is identified as Yokenella regensburgei. This rare bacterium is sensitive to most detected antibiotics. This study provides diagnostic and treatment experience for Yokenella regensburgei-related infections.

Transketolase (EC 2.2.1.1, TK) is a thiamine diphosphate-dependent enzyme that catalyzes the transfer of a two-carbon hydroxyacetyl unit with reversible C-C bond cleavage and formation. It is widely used in the production of chemicals, drug precursors, and asymmetric synthesis by cascade enzyme catalysis. In this paper, the activity of transketolase TKTA from Escherichia coli K12 on non-phosphorylated substrates was enhanced through site-directed saturation mutation and combined mutation. On this basis, the synthesis of tartaric semialdehyde was explored. The results showed that the optimal reaction temperature and pH of TKTA_M (R358I/H461S/R520Q) were 32 ℃ and 7.0, respectively. The specific activity on d-glyceraldehyde was (6.57±0.14) U/mg, which was 9.25 times higher than that of the wild type ((0.71±0.02) U/mg). Based on the characterization of TKTA_M, tartaric acid semialdehyde was synthesized with 50 mmol/L 5-keto-d-gluconate and 50 mmol/L non-phosphorylated ethanolaldehyde. The final yield of tartaric acid semialdehyde was 3.71 g with a molar conversion rate of 55.34%. Hence, the results may facilitate the preparation of l-(+)-tartaric acid from biomass, and provide an example for transketolase-catalyzed non-phosphorylated substrates.
Escherichia coli/genetics* ; Transketolase/chemistry* ; Tartrates ; Escherichia coli Proteins/genetics*