Bacteria of the Pseudomonas genus have been widely studied due to their antagonistic potential against a diverse group of fungal and bacterial phytopathogens, and their competence to colonize different plant tissues. We have isolated a rhizospheric pseudomonad that produced a black pigment, which is not a widespread trait within this genus. We confirmed that the isolate belonged to the P. putida complex through a MLSA analysis. We observed that the pigment synthesis was enhanced under high C:N ratios (25:1) and it was dependent of the carbon source, being maximized when we added glucose to M9. Besides, the supplementation of M9 with tryptophan inhibited the pigment production under C:N ratios of 4:1, and the addition of kojic acid reduced notably the pigment under favorable conditions. Ps. black presented several traits associated with plant-growth promoting potential with classical in vitro assays. Through a Tn5 mutagenesis approach, we found 2 representative clones, PB1 and PB5, that were consistently unable to produce the pigment under several growth conditions and were not altered in their in vitro probiotic traits. When comparing with PB1 and PB5 performances, we observed that the pigment gives Ps. black a higher tolerance to oxidative stress and UV radiation exposure. When confronting Ps. black with different bacterial phytopathogens, we demonstrated that Ps. black could inhibit in vitro the growth of Xanthomonas vesicatoria Bv5-4a, Pseudomonas syringae pv. tomato DC3000, P. syringae pv. syringae B728a, P. savastanoi pv. glycinea B076 and Clavibacter michiganensis subsp. michiganensis Cm9. Except for Psg B076, this antagonism was lost for PB1 and PB5 and when performing the test for Ps. black with tryptophan supplementation. Thus, we suggest that the pigment should be involved in the bacterial antagonisms, and that Ps black contains more than one antibacterial mechanism.

由于假单胞菌属细菌对多种真菌和细菌性植物病原体具有拮抗潜力，并且具有在不同植物组织中定殖的能力，因此已被广泛研究。我们已经分离出根际假单胞菌产生黑色素，这不是该属中的广泛性状。我们确认分离株属于恶臭假单胞菌通过MLSA分析获得复杂的结果。我们观察到，在高C：N比（25：1）下，颜料合成得到了增强，并且取决于碳源，当我们向M9中添加葡萄糖时，碳的合成得以最大化。此外，在色氨酸与M9的比例为4：1的情况下，色氨酸的添加会抑制颜料的产生，而曲酸的添加在有利条件下会显着降低颜料的含量。附言 黑色通过经典的体外测定显示了与植物生长促进潜力相关的几个特征。通过Tn 5诱变方法，我们发现了2个代表性克隆PB1和PB5，它们在几种生长条件下始终无法产生色素，并且在体外没有改变益生菌性状。与PB1和PB5的性能进行比较时，我们观察到颜料产生Ps。黑色对氧化应激和紫外线辐射的耐受性更高。当面对PS。黑色具有不同的细菌性植物病原体，我们证明了Ps。黑色能抑制体外生长黄vesicatoria Bv5-4a，野火光伏。番茄DC3000，丁香假单胞菌PV。丁香假单胞菌B728a ，p。savastanoi pv。glycinea B076和马铃薯环腐密执安亚种。密歇根州9厘米。除了Psg B076之外，PB1和PB5以及执行Ps测试时都失去了这种拮抗作用。黑色与色氨酸补充。因此，我们建议色素应参与细菌的拮抗作用，并且Ps黑包含多种抗菌机制。