棉花根系分泌物对枯草芽胞杆菌NCD-2生物膜形成和根际定殖的影响

 为明确棉花根系分泌物对生防枯草芽胞杆菌NCD-2生物膜形成的影响,本研究首先比较了菌株NCD-2在不同棉花品种(冀棉11、中棉所41、中植棉2号、鲁棉29和海岛棉Pima90)根际的定殖能力。结果表明,菌株NCD-2在Pima90的根际定殖能力最强,播种35 d后在根际的群体数量达到7.63×10⁵ CFU·g^-1根重;而在中植棉2号的根际定殖能力最弱,播种35 d后根际菌株NCD-2的群体数量为6.51×10⁴ CFU·g^-1根重。通过再循环水培系统收集根系分泌物的方法获得了不同棉花品种的根系分泌物,测定了其对菌株NCD-2生物膜形成的影响。结果表明,海岛棉Pima90的根系分泌物对该菌株生物膜形成的促进作用最强,而中植棉2号的根系分泌物对菌株NCD-2生物膜形成影响最弱。进一步分析了棉花根系分泌物中6种糖分和13种氨基酸对菌株NCD-2生物膜形成的影响,结果发现,葡聚糖和脯氨酸显著促进了该菌株的生物膜形成。

Effects of cotton root exudates on the biofilm formation and root colonization of Bacillus subtilis strain NCD-2

Bacillus subtilis strain NCD-2 is very effective in biocontrolling cotton soil-borne diseases. Previous studies showed that the biocontrol efficiency of strain NCD-2 was associated with its root colonization and biofilm formation capabilities. To clarify the influence of cotton root exudates on bacterial biofilm formation and root colonization, rhizosphere populations of strain NCD-2 were investigated on various cotton cultivars, including Jimian11, Zhongmiansuo41, Zhongzhimian2, Lumian29 and Pima90. It was showed that strain NCD-2 grew to form rhizosphere populations with different densities on different cultivars. The highest population of 7.63×10⁵ CFU·g^-1 root was achieved on cultivar Pima90 35 days after seeding, while the lowest of 6.51×10⁴ CFU·g^-1 root was on cultivar Zhongzhimian2 35 days after seeding. The root exudates collected from all 5 cultivars promoted the biofilm formation of strain NCD-2, among which the exudate from Pima90 had the strongest promoting effect, whereas the root exudate from Zhongtzhimian2 had only a slight effect. Six carbohydrates and thirteen amino acids found in the cotton root exudates were evaluated for their effects on bacterial biofilm formation. The results revealed that glucosan and proline significantly enhanced biofilm formation compared to other carbohydrates and amino acids, respectively