Lysobacter spp. are common bacterial inhabitants of the rhizosphere of diverse plant species. However, the impact of the rhizosphere conditions on their physiology is still relatively understudied. To provide clues on the behaviour of Lysobacter spp. in this ecological niche, we investigated the physiology of L. capsici AZ78 (AZ78), a biocontrol strain isolated from tobacco rhizosphere, on a common synthetic growth medium (LBA) and on a growth medium containing components of the plant rhizosphere (RMA). The presence of a halo surrounding the AZ78 colony on RMA was a first visible effect related to differences in growth medium composition and it corresponded to the formation of a large outer ring. The lower quantity of nutrients available in RMA as compared with LBA was associated to a higher expression of a gene encoding cAMP-receptor-like protein (Clp), responsible for cell motility and biofilm formation regulation. AZ78 cells on RMA were motile, equipped with cell surface appendages and organised in small groups embedded in a dense layer of fibrils. Metabolic profiling by mass spectrometry imaging revealed increased diversity of analytes produced by AZ78 on RMA as compared with LBA. In particular, putative cyclic lipodepsipeptides, polycyclic tetramate macrolactams, cyclic macrolactams and other putative secondary metabolites with antibiotic activity were identified. Overall, the results obtained in this study shed a light on AZ78 potential to thrive in the rhizosphere by its ability to move, form biofilm and release secondary metabolites.

溶杆菌属是多种植物根际的常见细菌居民。然而，根际条件对其生理的影响仍相对缺乏研究。提供有关溶杆菌属行为的线索。在这个生态位中，我们研究了辣椒L. capsici AZ78 (AZ78) 的生理学，这是一种从烟草根际分离的生物防治菌株，在常见的合成生长培养基 (LBA) 和含有植物根际成分的生长培养基 (RMA) 上。 RMA 上 AZ78 菌落周围光环的存在是与生长培养基成分差异相关的第一个可见效应，它对应于大外环的形成。与 LBA 相比，RMA 中可用的营养物质含量较低，这与编码 cAMP 受体样蛋白 (Clp) 的基因表达较高有关，该蛋白负责细胞运动和生物膜形成调节。 RMA 上的 AZ78 细胞具有运动能力，具有细胞表面附属物，并组织成小组，嵌入致密的原纤维层中。通过质谱成像进行的代谢分析显示，与 LBA 相比，RMA 上的 AZ78 产生的分析物多样性有所增加。特别是，鉴定了假定的环状脂缩肽、多环四酸酯大环内酰胺、环状大环内酰胺和其他假定的具有抗生素活性的次级代谢物。总体而言，本研究获得的结果揭示了 AZ78 通过其移动、形成生物膜和释放次生代谢物的能力在根际茁壮成长的潜力。