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十字花科黑腐病菌(Xanthomonas campestris pv.campestris,简称Xcc)能够产生大量的胞外多糖。胞外多糖商品名又称为黄原胶,具有广泛用途,在食品生产中可作为添加剂使用。为了得到不含黄色素的黄原胶,我们采用转座子EZ-Tn5随机插入诱变的方法对8004菌株进行突变,获得了一株不产黄色素的突变体。通过对突变体的转座子EZ-Tn5插入位点进行分析,发现该突变体是由于编号为XC_4097的基因被插入突变后衍生而来。同源性分析表明XC_4097编码一种脂质酰基转移酶,它与脂质的合成有关。采用同源双交换方法构建XC_4097基因的缺失突变体。通过对野生菌、突变体以及功能回补体的表型分析进一步证实了XC_4097基因功能的丧失只影响黑腐病菌黄色素的合成,而不影响细菌生长以及胞外多糖的合成。这为工业上生产无黄色素的黄原胶提供了应用基础。
Xanthomonas campestris pv. Campestris (Xcc) is capable of producing a large amount of extracellular polysaccharides. Exopolysaccharide trade name, also known as xanthan gum, has a wide range of uses in food production can be used as an additive. In order to obtain xanthan gum without yellow pigment, we mutated the 8004 strain by random insertion mutagenesis of the transposon EZ-Tn5 to obtain a mutant that does not produce yellow pigment. Through the analysis of the transposon EZ-Tn5 insertion site of the mutant, it was found that the mutant was derived after the insertion of the gene with the code XC_4097. Homology analysis revealed that XC_4097 encodes a lipid acyltransferase that is involved in lipid synthesis. Homology double crossover method was used to construct deletion mutant of XC_4097 gene. The phenotypic analysis of wild-type bacteria, mutants and functional complement further confirmed that the loss of XC-4097 gene function only affected the synthesis of yellow rot virus yellow pigment without affecting the growth of bacteria and the synthesis of exopolysaccharides. This provides the basis for the industrial production of yellow-free xanthan gum.