Galactose Metabolism Plays a Crucial Role in Biofilm Formation by Bacillus subtilis
Galactose Metabolism Plays a Crucial Role in Biofilm Formation by Bacillus subtilis
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DOI：
10.1128/mbio.00555-12
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发表时间：
2013-01-08
期刊：
影响因子：
6.4
通讯作者：
Kolter R
中科院分区：
文献类型：
--
作者：
Chai Y;Beauregard PB;Vlamakis H;Losick R;Kolter R
半乳糖是一种常见的单糖，可以通过构成Leloir途径的三种主要酶的活性被所有生物体利用：GalK，GalT和GalE。在枯草芽孢杆菌中，GalE的缺乏引起对外源半乳糖的敏感性，导致快速细胞裂解。这种效应可归因于毒性半乳糖代谢物的积累，因为galE突变体在半乳糖催化的最后一步被阻断。在半乳糖存在下恢复agalEnull突变体活力的抑制突变体的筛选中，我们鉴定了inR突变，其是主要的生物膜抑制基因。这些突变导致生物膜基质的胞外多糖（EPS）组分的产生增加。我们建议UDP-半乳糖是有毒的半乳糖代谢产物，它被用于合成EPS。因此，EPS的产生可以作为这种有毒分子的分流机制。此外，我们证明了半乳糖代谢基因在B中起着重要作用。枯草芽孢杆菌生物膜的形成和两个thegalandeps基因的表达是相互关联的。最后，我们提出B.枯草芽孢杆菌和其他芽孢杆菌属的成员可能已经进化到利用天然存在的半乳糖聚合物，如半乳聚糖作为碳源。重要提示细菌通过产生含有胞外多糖的细胞外基质从单细胞状态转变为多细胞状态。在这种被称为生物膜的聚集体中，细菌对抗生素的抗性更强。这使得生物膜成为临床环境中的严重问题。生物膜的弹性使其在工业环境中非常有用。因此，了解生物膜基质的产生是微生物学中的一个重要问题。在研究枯草芽孢杆菌的生物膜基质的合成，我们提供了一个长期的微生物学观察，某些突变体缺陷的利用半乳糖变得敏感it. In这项工作中，我们表明，以前观察到的毒性是因为细胞生长的条件下，是不利于生产的胞外多糖成分的矩阵，进一步了解。当细胞在有利于基质产生的条件下生长时，半乳糖的毒性被减轻。 这使我们能够证明半乳糖代谢是细胞外基质合成所必需的。
Galactose is a common monosaccharide that can be utilized by all living organisms via the activities of three main enzymes that make up the Leloir pathway: GalK, GalT, and GalE. In Bacillus subtilis, the absence of GalE causes sensitivity to exogenous galactose, leading to rapid cell lysis. This effect can be attributed to the accumulation of toxic galactose metabolites, since thegalEmutant is blocked in the final step of galactose catabolism. In a screen for suppressor mutants restoring viability to agalEnull mutant in the presence of galactose, we identified mutations insinR, which is the major biofilm repressor gene. These mutations caused an increase in the production of the exopolysaccharide (EPS) component of the biofilm matrix. We propose that UDP-galactose is the toxic galactose metabolite and that it is used in the synthesis of EPS. Thus, EPS production can function as a shunt mechanism for this toxic molecule. Additionally, we demonstrated that galactose metabolism genes play an essential role in B. subtilis biofilm formation and that the expressions of both thegalandepsgenes are interrelated. Finally, we propose that B. subtilis and other members of theBacillusgenus may have evolved to utilize naturally occurring polymers of galactose, such as galactan, as carbon sources.IMPORTANCEBacteria switch from unicellular to multicellular states by producing extracellular matrices that contain exopolysaccharides. In such aggregates, known as biofilms, bacteria are more resistant to antibiotics. This makes biofilms a serious problem in clinical settings. The resilience of biofilms makes them very useful in industrial settings. Thus, understanding the production of biofilm matrices is an important problem in microbiology. In studying the synthesis of the biofilm matrix of Bacillus subtilis, we provide further understanding of a long-standing microbiological observation that certain mutants defective in the utilization of galactose became sensitive to it. In this work, we show that the toxicity observed before was because cells were grown under conditions that were not propitious to produce the exopolysaccharide component of the matrix. When cells are grown under conditions that favor matrix production, the toxicity of galactose is relieved. This allowed us to demonstrate that galactose metabolism is essential for the synthesis of the extracellular matrix.