Both root nodules and the rhizosphere of Fabaceae plants grown on organic farms are a rich source of bacteria, mainly from the families Enterobacteriaceae and Pseudomonadaceae. The enhanced root system growth in M. truncatula after inoculation with selected bacteria includes an increase of nuclei in the cell cycle S phase and a reduction in phase G2 as well as an enhanced expression of the WOX5 gene. Synthetic fertilizers and pesticides are commonly used to improve plant quality and health. However, it is necessary to look for other efficient and also environmentally safe methods. One such method involves the use of bacteria known as plant growth-promoting bacteria (PGPB). Seventy-two bacterial isolates from the rhizospheric soil and root nodule samples of legumes, including bean, alfalfa, lupine and barrel medic, grown on an organic farm in Western Pomerania (Poland) were screened for their growth-promoting capacities and 38 selected isolates were identified based on 16S rRNA gene sequencing. The analysis showed the isolates to represent 17 strains assigned to 6 families: Enterobacteriaceae, Pseudomonadaceae, Xanthomonadaceae, Rhizobiaceae, Bacillaceae and Alcaligenaceae. Pot experiments showed that 13 strains, capable of producing indole compounds from tryptophan in vitro, could significantly enhance the root and shoot weight of 10-week-old Medicago truncatula seedlings. Compared to non-inoculated seedlings, the root system of inoculated ones was more branched; in addition, the root length, surface area and, especially, the root volume were higher. The 24-h root inoculation with the three selected strains increased the nuclei population in the G1 and S phases, decreased it in the G2 phase and enhanced the WUSCHEL-related Homeobox5 (WOX5) gene expression in root tips and lateral zones. The “arrest” of nuclei in the S phase and the enhancement of the WOX5 gene expression were observed to gradually disappear once the bacterial suspension was rinsed off the seedling roots and the roots were transferred to water for further growth. This study shows that the nodules and rhizosphere of legumes grown on organic farms are a rich source of different PGPB species and provides new data on the ability of these bacteria to interfere with cell cycle and gene expression during the root development.

中文翻译：

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从豆科植物中分离出的促进生长的微生物对蒺藜苜蓿根的发育变化，在有机农场生长，涉及细胞周期变化和 WOX5 基因表达

在有机农场种植的豆科植物的根瘤和根际都是细菌的丰富来源，主要来自肠杆菌科和假单胞菌科。用选定的细菌接种后，蒺藜苜蓿根系生长增强，包括细胞周期 S 期细胞核的增加和 G2 期的减少以及 WOX5 基因的表达增强。合成肥料和杀虫剂通常用于改善植物质量和健康。然而，有必要寻找其他有效且对环境安全的方法。一种这样的方法涉及使用称为植物生长促进细菌 (PGPB) 的细菌。从豆科植物的根际土壤和根瘤样本中分离出 72 种细菌，包括豆类、苜蓿、羽扇豆和桶状药材，对在西波美拉尼亚（波兰）的一个有机农场种植的植物进行了生长促进能力筛选，并根据 16S rRNA 基因测序鉴定了 38 个选定的分离株。分析表明，分离物代表 17 个菌株，分为 6 个科：肠杆菌科、假单胞菌科、黄单胞菌科、根瘤菌科、芽孢杆菌科和产碱菌科。盆栽试验表明，13株能够在体外从色氨酸中产生吲哚类化合物的菌株，可以显着提高10周龄蒺藜苜蓿幼苗的根茎重量。与未接种苗相比，接种苗的根系分枝较多；此外，根长、表面积，尤其是根体积更高。3 种选定菌株的 24 小时根接种增加了 G1 和 S 期的细胞核数量，减少了 G2 期的细胞核数量，并增强了根尖和侧区的 WUSCHEL 相关 Homeobox5 (WOX5) 基因表达。一旦将细菌悬浮液从幼苗根部冲洗掉并将根部转移到水中以进一步生长，观察到S期细胞核的“停滞”和WOX5基因表达的增强逐渐消失。这项研究表明，有机农场种植的豆科植物的根瘤和根际是不同 PGPB 物种的丰富来源，并为这些细菌在根系发育过程中干扰细胞周期和基因表达的能力提供了新数据。在 G2 期降低了它并增强了根尖和侧区中 WUSCHEL 相关的 Homeobox5 (WOX5) 基因表达。一旦将细菌悬浮液从幼苗根部冲洗掉并将根部转移到水中以进一步生长，观察到S期细胞核的“停滞”和WOX5基因表达的增强逐渐消失。这项研究表明，有机农场种植的豆科植物的根瘤和根际是不同 PGPB 物种的丰富来源，并为这些细菌在根系发育过程中干扰细胞周期和基因表达的能力提供了新数据。在 G2 期降低了它并增强了根尖和侧区中 WUSCHEL 相关的 Homeobox5 (WOX5) 基因表达。一旦将细菌悬浮液从幼苗根部冲洗掉并将根部转移到水中以进一步生长，观察到S期细胞核的“停滞”和WOX5基因表达的增强逐渐消失。这项研究表明，有机农场种植的豆科植物的根瘤和根际是不同 PGPB 物种的丰富来源，并为这些细菌在根系发育过程中干扰细胞周期和基因表达的能力提供了新数据。一旦将细菌悬浮液从幼苗根部冲洗掉并将根部转移到水中以进一步生长，观察到S期细胞核的“停滞”和WOX5基因表达的增强逐渐消失。这项研究表明，有机农场种植的豆科植物的根瘤和根际是不同 PGPB 物种的丰富来源，并为这些细菌在根系发育过程中干扰细胞周期和基因表达的能力提供了新数据。一旦将细菌悬浮液从幼苗根部冲洗掉并将根部转移到水中以进一步生长，观察到S期细胞核的“停滞”和WOX5基因表达的增强逐渐消失。这项研究表明，有机农场种植的豆科植物的根瘤和根际是不同 PGPB 物种的丰富来源，并为这些细菌在根系发育过程中干扰细胞周期和基因表达的能力提供了新数据。