The widely conserved twin-arginine translocases (Tat) allow the transport of fully folded cofactor-containing proteins across biological membranes. In doing so, these translocases serve different biological functions ranging from energy conversion to cell division. In the Gram-positive soil bacterium Bacillus subtilis, the Tat machinery is essential for effective growth in media lacking iron or NaCl. It was previously shown that this phenomenon relates to the Tat-dependent export of the heme-containing peroxidase EfeB, which converts Fe²⁺ to Fe³⁺ at the expense of hydrogen peroxide. However, the reasons why the majority of tat mutant bacteria perish upon dilution in NaCl-deprived medium and how, after several hours, a sub-population adapts to this condition was unknown. Here we show that, upon growth in the absence of NaCl, the bacteria face two major problems, namely severe oxidative stress at the membrane and starvation leading to death. The tat mutant cells can overcome these challenges if they are fed with arginine, which implies that severe arginine depletion is a major cause of death and resumed arginine synthesis permits their survival. Altogether, our findings show that the Tat system of B. subtilis is needed to preclude severe oxidative stress and starvation upon sudden drops in the environmental Na⁺ concentration as caused by flooding or rain.

广泛保存的双精氨酸转位酶（Tat）允许跨生物膜运输完全折叠的含辅因子蛋白。这样，这些转位酶具有不同的生物学功能，从能量转换到细胞分裂。在革兰氏阳性土壤细菌枯草芽孢杆菌中，Tat机制对于在缺​​乏铁或NaCl的培养基中有效生长至关重要。先前已表明，这种现象与Tat依赖的含血红素的过氧化物酶EfeB的输出有关，EfeB可以将Fe ²⁺转化为Fe ³⁺，而过氧化氢却是代价。但是，为什么达达人多数突变细菌在稀释了NaCl的培养基中稀释后会消失，并且几个小时后，亚种群如何适应这种情况仍是未知的。在这里，我们表明，在没有NaCl的情况下生长时，细菌面临两个主要问题，即膜上的严重氧化应激和导致死亡的饥饿。如果将tat突变细胞饲喂精氨酸，它们可以克服这些挑战，这意味着精氨酸的严重消耗是主要的死亡原因，精氨酸合成的恢复使它们得以存活。总的来说，我们的发现表明，枯草芽孢杆菌的Tat系统需要用来防止由于洪水或雨水引起的环境Na ⁺浓度突然下降时严重的氧化应激和饥饿。