title: Metabolic and genetic factors affecting the productivity of pyrimidine nucleoside in Bacillus subtilis.
abstract: BACKGROUND
  Cytidine and uridine are produced commercially by Bacillus subtilis. The production strains of cytidine and uridine were both derivatives from mutagenesis. However, the exact metabolic and genetic factors affecting the productivity remain unknown. Genetic engineering may be a promising approach to identify and confirm these factors.
  
  
  RESULTS
  With the deletion of the cdd and hom genes, and the deregulation of the pyr operon in Bacillus subtilis168, the engineered strain produced 200.9 mg/L cytidine, 14.9 mg/L uridine and 960.1 mg/L uracil. Then, the overexpressed prs gene led to a dramatic increase of uridine by 25.9 times along with a modest increase of cytidine. Furthermore, the overexpressed pyrG gene improved the production of cytidine, uridine and uracil by 259.5%, 11.2% and 68.8%, respectively. Moreover, the overexpression of the pyrH gene increasesd the yield of cytidine by 40%, along with a modest augments of uridine and uracil. Lastly, the deletion of the nupC-pdp gene resulted in a doubled production of uridine up to 1684.6 mg/L, a 14.4% increase of cytidine to 1423 mg/L, and a 99% decrease of uracil to only 14.2 mg/L.
  
  
  CONCLUSIONS
  The deregulation of the pyr operon and the overexpression of the prs, pyrG and pyrH genes all contribute to the accumulation of pyrimidine nucleoside compounds in the medium. Among these factors, the overexpression of the pyrG and pyrH genes can particularly facilitate the production of cytidine. Meanwhile, the deletion of the nupC-pdp gene can obviously reduce the production of uracil and simultaneously improve the production of uridine.
authors.affiliation: Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China. zhuhui0505@hotmail.com.|Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin, 300072, China. zhuhui0505@hotmail.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China. shaomei@tju.edu.cn.|Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin, 300072, China. shaomei@tju.edu.cn.
authors.forename: Shao-Mei
authors.initials: SM
authors.lastname: Yang
authors.affiliation: Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China. yuanzhaomin@tju.edu.cn.|Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin, 300072, China. yuanzhaomin@tju.edu.cn.
authors.forename: Zhao-Min
authors.initials: ZM
authors.lastname: Yuan
authors.affiliation: Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China. banrui@tju.edu.cn.|Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin, 300072, China. banrui@tju.edu.cn.
authors.forename: Rui
authors.initials: R
authors.lastname: Ban
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018533:Biomass; D003562:Cytidine / Q000096:biosynthesis*; D003564:Cytidine Deaminase / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006715:Homoserine Dehydrogenase / Q000235:genetics / Q000378:metabolism; D060847:Metabolic Engineering / Q000379:methods; D016296:Mutagenesis; D009876:Operon / Q000235:genetics; D010430:Pentosyltransferases / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014529:Uridine / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D003562:Cytidine; D006715:Homoserine Dehydrogenase; D010430:Pentosyltransferases; C098851:PyrR protein, bacteria; D003564:Cytidine Deaminase; D014529:Uridine