Spermidine (Spd), spermine (Spm), and putrescine (Put), which are the most widely distributed cellular polyamines, are essential for normal growth and multiplication of both eukaryotic and prokaryotic cells. In this study, we identified the only putative polyamine transport system PotABCD in Streptococcus suis, a worldwide zoonotic Gram-positive pathogen causing lethal infections in humans and pigs. It was discovered that S. suis could uptake polyamines preferably Spd and Spm. By constructing a potA deleted mutant, we confirmed that PotABCD was responsible for polyamine uptake, and PotD bound to the protein of polyamines. The four PotABCD genes were co-transcribed with murB, a gene involved in peptidoglycan (PG) synthesis. Furthermore the roles of polyamine transport system in maintaining the PG structure were detected to understand the biological significance of this co-transcription. In contrast to the wild type, the mutant ΔpotA exhibited elongated chain length and abnormal cell division morphology. Phenotypic changes were attributed to be the up-regulation of genes involved in PG synthesis and hydrolysis in ΔpotA. Additionally, polyamines functioned not only as feedback regulators of PotA by inhibiting PotA activity but also as regulators on potABCD and genes involved in PG synthesis. This study reveals the functions of PotABCD in polyamine transport and the regulatory roles of polyamines in PG synthesis. Results provide new insights into the machineries contributing to normal growth and cell division of S. suis.

亚精胺（Spd），精胺（Spm）和腐胺（Put）是分布最广泛的细胞多胺，对于真核和原核细胞的正常生长和繁殖至关重要。在这项研究中，我们在猪链球菌中发现了唯一推定的多胺转运系统PotABCD，猪链球菌是一种在世界范围内引起人和猪致命感染的人畜共患的革兰氏阳性病原体。发现猪链球菌可以摄取多胺，优选为Spd和Spm。通过构建potA缺失的突变体，我们证实PotABCD负责多胺的摄取，并且PotD与多胺的蛋白质结合。四个PotABCD基因与murB共转录是参与肽聚糖（PG）合成的基因。此外，检测了多胺转运系统在维持PG结构中的作用，以了解这种共转录的生物学意义。与野生型相反，突变体ΔpotA表现出延长的链长和异常的细胞分裂形态。表型的变化归因于参与ΔpotA中PG合成和水解的基因的上调。此外，多胺不仅通过抑制PotA活性而充当PotA的反馈调节剂，而且还充当potABCD上的调节剂。和参与PG合成的基因。这项研究揭示了PotABCD在多胺运输中的功能以及多胺在PG合成中的调节作用。结果为有助于猪链球菌正常生长和细胞分裂的机制提供了新的见识。