该研究发现,发酵培养基中添加一定浓度的腺嘌呤/鸟嘌呤/黄嘌呤/次黄嘌呤会对枯草芽孢杆菌R的核黄素合成产生抑制。而在R中单独敲除7种嘌呤转运蛋白基因pbuG、nupG、pbuE、ywdJ、nupNOPQ、pbuX、pbuO后会分别减弱或增强嘌呤碱的抑制作用。将抑制作用变化所表征的转运蛋白功能与通过生长实验鉴定的转运蛋白的功能相结合,对这些转运蛋白的功能进行了判断。其中NupNOPQ、PbuX、PbuO具有腺嘌呤内运功能,PbuG和PbuO具有鸟嘌呤内运功能。在R中单独敲除nupNOPQ、pbuX和pbuG后核黄素产量分别提高了10.74%、5.84%、7.53%。而组合敲除三者后核黄素产量提高了19.14%,证明了嘌呤转运蛋白的敲除在提高枯草芽孢杆菌核黄素产量中具有一定作用。
The addition of adenine/guanine/xanthine/hypoxanthine with a certain concentration could inhibit the riboflavin synthesis of Bacillus subtilis R. In strain R, deletion of one of the seven purine transporter genes (pbuG, nupG, pbuE, ywdJ, nupNOPQ, pbuX, and pbuO) could diminish or intensify the inhibition of purine bases on riboflavin production. The functions of the transporters were deduced from the combination of the riboflavin production of the deletion mutants treated with purine bases and the growth phenotypes of the deletion mutants. Among these transporters, NupNOPQ, PbuX, and PbuO could import adenine, while PbuG and PbuO could import guanine. After knocked out nupNOPQ, pbuX, and pbuG in strain R, the production of riboflavin increased by 10.74%, 5.84%, and 7.53%, respectively. When all of the three genes were knocked out, the production of riboflavin increased by 19.14%. These results indicated that the deletion of purine transporters is effective in increasing riboflavin production.
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