Acinetobacter baumannii is outstanding for its ability to cope with low water activities and therefore its adaptation mechanism to osmotic stress. Here we report on the identification and characterization of five different secondary active compatible solute transporters, belonging to the betaine‐choline‐carnitine transporter (BCCT) family. Our studies revealed two choline‐specific and three glycine betaine‐specific BCCTs. Activity of the BCCTs was differentially dependent to the osmolality: one choline and one betaine transporter were osmostress‐independent. Addition of choline to resting cells of Acinetobacter grown in the presence of the co‐substrate choline or with phosphatidylcholine as sole carbon source led to ATP synthesis in the wild type but not in the BCCT quadruple mutant. This indicates that the BCCTs are essential to transport the energy substrate choline. The role of the different BCCTs in osmostress resistance and in metabolic adaptation of A . baumannii to the human host is discussed.

中文翻译：

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鲍曼不动杆菌中依赖于渗透压和不依赖于渗透压的甜菜碱-胆碱-肉碱转运蛋白的鉴定：在渗透压保护和代谢适应中的作用。

鲍曼不动杆菌因其应付低水分活动的能力而著称，因此其对渗透胁迫的适应机制也很出色。在这里我们报告了甜菜碱-胆碱-肉碱转运蛋白（BCCT）家族的五个不同的次要活性相容溶质转运蛋白的鉴定和表征。我们的研究揭示了两种胆碱特异性和三种甘氨酸甜菜碱特异性BCCT。BCCTs的活性与重量克分子渗透压浓度有不同的依赖性：一种胆碱和一种甜菜碱转运蛋白与渗透压无关。向不动杆菌的静止细胞中添加胆碱在共底物胆碱存在下或以磷脂酰胆碱作为唯一碳源生长时，可在野生型中导致ATP合成，但在BCCT四重突变体中则不会。这表明BCCT对运输能量底物胆碱至关重要。不同BCCT在A的渗透压抵抗和代谢适应中的作用。讨论了对人类宿主的鲍曼不动杆菌。