Physiological function of thiaminase Ⅰ derived from myxobacteria
Three genera of myxobacteria including Corallococcus sp.EGB,Myxococcus xanthus DK1622 and Cystobacter sp.1404 were used to study the physiological function of thiamine I from myxo-bacteria.The relationship between the pathway of synthesizing thiamine and the growth and development of strain in the genomes of three myxobacteria was identified.The results showed that three myxobacteria had complete pathway of synthesizing thiamine in their genomes,and contained genes related to the recovery of thiamine precursor pyrimidine(4-amino-5-hydroxymethyl-2-methylpyrimidine,HMP),but no genes relat-ed to the recovery of thiamine or its precursor thiazole was found.The presence of TPP-riboswitch at the upstream of the HMP synthase gene thiC regulated the transcription level of the thiC gene based on the concentration of thiamine in the environment.Mutant CL1006 and Mutant CL1007 were constructed by in-serting the thiC gene into strain DK1622 and thiaminase I knockout mutant CL1003,respectively.It was found that CL1006 required additional addition of thiamine or HMP to recover growth in thiamine-free me-dium.The HMP treatment group significantly increased the colony diameter by 9.0%compared to the thia-mine-treated group.CL1007 only grew on HMP plates,and the addition of intact thiamine alone did not re-store its growth.However,when CcThi1 and thiamine were added together,the growth of CL1007 was restored.It is indicated that myxobacteria do not directly utilize exogenous thiamine,but can utilize pyrimi-dine precursors produced by decomposing thiamine through thiaminase I.
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