National Oceanography Centre, Southampton, SO14 3ZH, UK.
School of Life Sciences, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, UK.
Nat Commun. 2020 May 26;11(1):2642. doi: 10.1038/s41467-020-16428-w.
Bacteria acquire phosphate (P) by maintaining a periplasmic concentration below environmental levels. We recently described an extracellular P buffer which appears to counteract the gradient required for P diffusion. Here, we demonstrate that various treatments to outer membrane (OM) constituents do not affect the buffered P because bacteria accumulate P in the periplasm, from which it can be removed hypo-osmotically. The periplasmic P can be gradually imported into the cytoplasm by ATP-powered transport, however, the proton motive force (PMF) is not required to keep P in the periplasm. In contrast, the accumulation of P into the periplasm across the OM is PMF-dependent and can be enhanced by light energy. Because the conventional mechanism of P-specific transport cannot explain P accumulation in the periplasm we propose that periplasmic P anions pair with chemiosmotic cations of the PMF and millions of accumulated P pairs could influence the periplasmic osmolarity of marine bacteria.
细菌通过将周质内的浓度维持在环境水平以下来获取磷酸盐 (P)。我们最近描述了一种细胞外的 P 缓冲液，它似乎可以抵消 P 扩散所需的梯度。在这里，我们证明了对外膜 (OM) 成分的各种处理不会影响缓冲 P，因为细菌可以从周质中积累 P，然后通过低渗作用将其去除。周质中的 P 可以通过 ATP 驱动的运输逐渐被导入细胞质，但不需要质子动力势 (PMF) 来保持 P 在周质中。相比之下，P 通过 OM 进入周质的积累是 PMF 依赖性的，并且可以通过光能增强。由于传统的 P 特异性运输机制无法解释 P 在周质中的积累，我们提出周质中的 P 阴离子与 PMF 的化学渗透阳离子配对，并且数百万个积累的 P 对可能会影响海洋细菌的周质渗透压。
