Schwalm Nathan D, Townsend Guy E, Groisman Eduardo A
Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT, USA.
Yale Microbial Sciences Institute, West Haven, CT, USA.
Mol Microbiol. 2017 Apr;104(1):32-45. doi: 10.1111/mmi.13609. Epub 2017 Feb 3.
Bacteroides thetaiotaomicron is a human gut symbiotic bacterium that utilizes a myriad of host dietary and mucosal polysaccharides. The proteins responsible for the uptake and breakdown of many of these polysaccharides are transcriptionally regulated by hybrid two-component systems (HTCSs). These systems consist of a single polypeptide harboring the domains of sensor kinases and response regulators, and thus, are thought to autophosphorylate in response to specific signals. We now report that the HTCS BT0366 is phosphorylated in vivo when B. thetaiotaomicron experiences the BT0366 inducer arabinan but not when grown in the presence of glucose. BT0366 phosphorylation and transcription of BT0366-activated genes requires the conserved predicted sites of phosphorylation in BT0366. When chondroitin sulfate is added to arabinan-containing cultures, BT0366 phosphorylation and transcription of BT0366-activated genes are inhibited and the bacterium exhibits diauxic growth. Whereas 20 additional combinations of polysaccharides also give rise to diauxic growth, other combinations result in synergistic or unaltered growth relative to bacteria experiencing a single polysaccharide. The different strategies employed by B. thetaiotaomicron when faced with multiple polysaccharides may aid its competitiveness in the mammalian gut.
嗜热栖热放线菌是一种人类肠道共生细菌，它能利用多种宿主饮食和黏膜多糖。负责摄取和分解许多这些多糖的蛋白质受混合双组分系统（HTCSs）转录调控。这些系统由一个包含传感器激酶和反应调节因子结构域的单一多肽组成，因此被认为会响应特定信号进行自磷酸化。我们现在报告，当嗜热栖热放线菌遇到BT0366诱导剂阿拉伯聚糖时，HTCS BT0366在体内会被磷酸化，但在葡萄糖存在下生长时则不会。BT0366的磷酸化以及BT0366激活基因的转录需要BT0366中保守的预测磷酸化位点。当向含阿拉伯聚糖的培养物中添加硫酸软骨素时，BT0366的磷酸化以及BT0366激活基因的转录受到抑制，并且该细菌呈现双相生长。虽然另外20种多糖组合也会导致双相生长，但其他组合相对于只接触一种多糖的细菌会导致协同生长或生长无变化。嗜热栖热放线菌在面对多种多糖时采用的不同策略可能有助于其在哺乳动物肠道中的竞争力。
