School of Life Sciences, University of Warwick, Gibbet Hill Road, Coventry, UK.
School of Agriculture, Policy, and Development, University of Reading, Earley Gate, Whiteknights, Reading, UK.
Environ Microbiol. 2022 Apr;24(4):1902-1917. doi: 10.1111/1462-2920.15959. Epub 2022 Mar 8.
Bacteria possess various regulatory mechanisms to detect and coordinate a response to elemental nutrient limitation. In pseudomonads, the two-component system regulators CbrAB, NtrBC and PhoBR, are responsible for regulating cellular response to carbon (C), nitrogen (N) and phosphorus (P) respectively. Phosphonates are reduced organophosphorus compounds produced by a broad range of biota and typified by a direct C-P bond. Numerous pseudomonads can use the environmentally abundant phosphonate species 2-aminoethylphosphonate (2AEP) as a source of C, N, or P, but only PhoBR has been shown to play a role in 2AEP utilization. On the other hand, utilization of 2AEP as a C and N source is considered substrate inducible. Here, using the plant-growth-promoting rhizobacterium Pseudomonas putida BIRD-1 we present evidence that 2AEP utilization is under dual regulation and only occurs upon depletion of C, N, or P, controlled by CbrAB, NtrBC, or PhoBR respectively. However, the presence of 2AEP was necessary for full gene expression, i.e. expression was substrate inducible. Mutation of a LysR-type regulator, termed AepR, upstream of the 2AEP transaminase-phosphonatase system (PhnWX), confirmed this dual regulatory mechanism. To our knowledge, this is the first study identifying coordination between global stress response and substrate-specific regulators in phosphonate metabolism.
细菌拥有各种调节机制来检测和协调对元素营养限制的反应。在假单胞菌中，双组分系统调节剂 CbrAB、NtrBC 和 PhoBR 分别负责调节细胞对碳 (C)、氮 (N) 和磷 (P) 的反应。膦酸盐是广泛的生物产生的还原有机磷化合物，其特点是直接 C-P 键。许多假单胞菌可以利用环境中丰富的膦酸盐种类 2-氨基乙基膦酸盐 (2AEP) 作为 C、N 或 P 的来源，但只有 PhoBR 被证明在 2AEP 利用中发挥作用。另一方面，2AEP 作为 C 和 N 源的利用被认为是底物诱导的。在这里，我们使用植物促生根际细菌 Pseudomonas putida BIRD-1 提供证据表明，2AEP 的利用受到双重调节，只有在 C、N 或 P 耗尽时才会发生，分别由 CbrAB、NtrBC 或 PhoBR 控制。然而，2AEP 的存在对于完全基因表达是必要的，即表达是底物诱导的。在 2AEP 转氨酶-膦酸酶系统 (PhnWX) 上游的 LysR 型调节剂 AepR 的突变证实了这种双重调节机制。据我们所知，这是首次在膦酸盐代谢中确定全局应激反应与底物特异性调节剂之间的协调。
