Dell'Amico Elena, Cavalca Lucia, Andreoni Vincenza
Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, Via Celoria 2, 20133 Milan, Italy.
FEMS Microbiol Ecol. 2005 Apr 1;52(2):153-62. doi: 10.1016/j.femsec.2004.11.005. Epub 2004 Dec 22.
This study investigates the impact of long-term heavy metal contamination on the culturable, heterotrophic, functional and genetic diversity of rhizobacterial communities of perennial grasses in water meadow soil. The culturable heterotrophic diversity was investigated by colony appearance on solid LB medium. Genetic diversity was measured as bands in denaturing gradient gel electrophoresis (DGGE) obtained directly from rhizosphere soil and rhizoplane DNA extracts, and from the corresponding culturable communities. In the two rhizospheric fractions the DGGE profiles of the direct DNA extracts were similar and stable among replicates, whereas in the enriched cultures the profiles of the fractions differed, but among the replicates they were similar. One hundred isolates were collected into 33 different operational taxonomic units by use of amplified internal transcribed spacers and into 19 heavy metal-resistant phenotypes. The phylogenetic position of strains belonging to 18 operational taxonomic units, representing more than 80% of the isolates, was determined by 16S rRNA gene sequencing. Several heavy metal-resistant strains were isolated from rhizoplane. Finally, metal-resistant rhizobacteria were tested for plant growth-promoting characteristics; some were found to contain 1-aminocyclopropane-1-carboxylic acid deaminase and/or to produce indole acetic acid and siderophores. Two strains resistant to cadmium and zinc, Pseudomonas tolaasii RP23 and Pseudomonas fluorescens RS9, had all three plant growth-promoting characteristics. Our findings suggest that bacteria can respond to soil metal contamination, and the described methodological approach appears promising for targeting potential plant growth-promoting rhizobacteria.
本研究调查了长期重金属污染对水涝地土壤中多年生禾本科植物根际细菌群落的可培养、异养、功能和遗传多样性的影响。通过在固体LB培养基上的菌落形态来研究可培养异养多样性。遗传多样性通过直接从根际土壤和根表DNA提取物以及相应的可培养群落中获得的变性梯度凝胶电泳（DGGE）条带进行测定。在两个根际部分中，直接DNA提取物的DGGE图谱在重复样本间相似且稳定，而在富集培养物中，各部分的图谱不同，但在重复样本间相似。通过使用扩增的内转录间隔区，将100个分离株归为33个不同的操作分类单元，并归为19种重金属抗性表型。通过16S rRNA基因测序确定了属于18个操作分类单元的菌株的系统发育位置，这些单元代表了超过80%的分离株。从根表分离出了几种重金属抗性菌株。最后，对金属抗性根际细菌进行了植物促生特性测试；发现一些菌株含有1-氨基环丙烷-1-羧酸脱氨酶和/或能产生吲哚乙酸和铁载体。两种对镉和锌具有抗性的菌株，即托拉斯假单胞菌RP23和荧光假单胞菌RS9，具有所有这三种植物促生特性。我们的研究结果表明，细菌能够对土壤金属污染做出反应，并且所描述的方法对于靶向潜在的植物促生根际细菌似乎很有前景。
