Little is known about how seedlings sense new soil environments and how the rhizosphere bacteriome changes accordingly. It is important to elucidate these changes to better understand feedbacks that contribute to nutrient cycling and plant fitness. Here, we explored how the tomato rhizosphere bacteriome developed weekly throughout the vegetative developmental stage and with variable nitrogen (N) fertilizer additions. Bacterial communities expressing diverse functions highly fluctuated in the first and second week after planting, and these fluctuations diminished progressively after the third week. Bacteria capable of biocontrol stabilized after the fourth week, while those involved in nutrient cycling continued to change in abundance week-to-week. Thus, bacterial specialization may be concomitant with bacteriome stabilization. With N fertilizer application, bacteria with diverse functions continued to fluctuate through the fifth week. However, regardless of fertilization, bacterial communities stabilized by the sixth week. It may take two weeks for roots to select for soil bacteria to assemble a specific rhizosphere bacteriome, but when N is applied, this period extends. Subsequently, roots may select for bacteria that are already established in the rhizosphere rather than from the bulk soil. This study showcases the dynamics of rhizosphere assemblage and how this process is affected by N additions.

关于幼苗如何感知新的土壤环境以及根际细菌组如何相应地变化，我们知之甚少。阐明这些变化以更好地了解有助于养分循环和植物适应性的反馈非常重要。在这里，我们探讨了番茄根际细菌组在整个营养发育阶段如何每周发育，并在添加可变氮 （N） 肥料的情况下。表达多种功能的细菌群落在种植后第1周和第2周波动较大，第3周后波动逐渐减弱。能够进行生物控制的细菌在第 4 周后稳定下来，而那些参与营养循环的细菌每周的丰度继续变化。因此，细菌特化可能伴随着细菌组稳定。施用氮肥后，功能多样的细菌在第 5 周继续波动。然而，无论受精与否，细菌群落在第 6 周时都趋于稳定。根系可能需要两周时间才能选择土壤细菌来组装特定的根际细菌组，但是当施用 N 时，这个时期会延长。随后，根可能会选择已经在根际建立的细菌，而不是从大块土壤中选择。本研究展示了根际组合的动力学以及这一过程如何受到 N 添加的影响。