耐铜苏丹草根内生细菌的分离筛选及其生物学特性研究

从生长在铜矿废弃地土壤中的Cu耐性苏丹草根中分离筛选到二株产1-氨基环丙烷-1-羧酸(ACC)脱氨酶内生细菌K1-6和K3-9菌株,并对菌株生物学特性进行了研究。菌株K1-6和K3-9具有较强的Cu抗性和多种抗生素抗性,菌株K1-6和K3-9能够溶磷和分泌吲哚乙酸(IAA),另外,菌株K3-9还能够产生铁载体和精氨酸脱羧酶,菌株K1-6和K3-9对温度、p H和盐浓度具有一定的耐受性,经16S r DNA序列分析,菌株K1-6和K3-9分别被鉴定为根瘤菌属(Rhizobium sp.K1-6)和肠杆菌属(Enterobacter aerogenes K3-9)。采用平皿培养试验研究了菌株K1-6和K3-9对生长在不同浓度Cu(0、4 mg/L)环境中的苏丹草的生长和吸收Cu的影响。结果表明,接菌处理苏丹草根部和地上部干重分别比对照增加了10.6%~45.5%和13%~40%,差异达显著水平(P0.05);接菌株K1-6处理苏丹草根部和地上部Cu含量比对照增加了46%和85%(P0.05),而接菌株K3-9处理苏丹草根部和地上部Cu含量与对照相比没有显著差异。另外,接菌株K1-6处理苏丹草根部和地上部总Cu吸收量比对照增加了88%和114%(P0.05),接菌株K3-9处理苏丹草根部总Cu吸收量比对照增加了44%(P0.05)。另外,接菌株K1-6和K3-9处理的苏丹草根部吸收的Cu是地上部吸收Cu的16~23倍。研究表明,分离自耐铜苏丹草根部的内生细菌具有多种植物促生特性,能够显著促进苏丹草的生长、提高苏丹草对Cu的耐受性,并强化苏丹草根部对Cu的富集能力。另外,不同的内生细菌对苏丹草的生长、富集和耐受Cu的影响不同。

Isolation of Endophytic Bacteria from Roots of Cu-tolerant Sorghum sudanense and Their Biological Characteristics

Two ACC deaminase-producing endophytic bacteria (K1-6 and K3-9) were obtained from the roots of Cu-tolerant Sorghum sudanens grown in Cu mine wasteland. The biological characteristics of the two endophytic bacterial strains were characterized. Strains K1-6 and K3-9 showed resistance to high levels of Cu and antibiotics, solubilized inorganic phosphate, and produced indole acetic acid (IAA). Strain K3-9 could also produce siderophores and arginine decarboxylase. Strains K1-6 and K3-9 had also the characteristics of acid or alkali and salt tolerance and temperature resistance. Strains K1-6 and K3-9 were identified as Rhizobium sp. K1-6 and Enterobacter aerogenes K3-9 based on the analyses of their 16S rDNA gene sequences, respectively. Plate culture experiment was used to investigate the effects of the two endophytic bacterial strains on the growth and Cu accumulation of Sorghum sudanens grown in 0 and 4 mg/L of Cu added as CuSO₄. The results showed that significant (P<0.05) increase was observed in the root (ranging from 10.6% to 45.5%) and above-ground tissue (ranging from 13% to 40%) dry weight of the bacteria-inoculated Sorghum sudanens compared with the control. Inoculation with strain K1-6 was found to significantly increase Cu contents of the roots and above-ground tissues of Sorghum sudanens compared with the control, however, no significant difference was observed in Cu contents of the roots and above-ground tissues between the strain K3-9-inoculated and control plants. Furthermore, total Cu uptakes of the roots and above-ground tissues of the plants inoculated with strain K1-6 were increased by 88% and 114% (P<0.05) respectively compared with the control, while total Cu uptakes of the roots was increased by 44% in the presence of strain K3-9 compared with the control. Notably, Cu content of the roots was 16-23-fold higher than that of the above-ground tissues of the plants inoculated with the two strains. The above results showed that the endophytic bacterial strains K1-6 and K3-9 from the roots of Cu-tolerantSorghum sudanens have the innate multiple plant growth-promoting traits, can increase the growth and Cu tolerance of Sorghum sudanens, and enhance Cu accumulation in the roots. In addition, the increases in the growth, Cu accumulation and tolerance of Sorghum sudanens are dependent on the strains.