Ciccillo Fabio, Fiore Alessia, Bevivino Annamaria, Dalmastri Claudia, Tabacchioni Silvia, Chiarini Luigi
ENEA - C. R. Casaccia, Dip. to Innovazione, Unità Biotecnologie, Via Anguillarese 301, 00060 S. Maria di Galeria, Rome, Italy.
Environ Microbiol. 2002 Apr;4(4):238-45. doi: 10.1046/j.1462-2920.2002.00291.x.
In order to acquire a better understanding of the effects of the different delivery modes of bacterial inoculants on plant growth and on the community structure of rhizosphere bacterial populations, Burkholderia ambifaria MCI 7 (formerly B. cepacia MCI 7) was inoculated into the rhizosphere of maize plants by either seed adhesion or incorporation into soil. Plant growth was evaluated at different inoculum concentrations. The community structure of rhizosphere bacterial populations was evaluated by analysing the restriction patterns of the DNA coding for 16S rRNA amplified by polymerase chain reaction (PCR) (ARDRA) of 745 bacterial isolates. A number of diversity indices (richness, Shannon diversity, evenness and mean genetic distance) were calculated for each bacterial population isolated from control and treated plants according to the concept of the r/K strategy. Moreover, the analysis of molecular variance (AMOVA) method was applied to estimate the genetic differences among the various bacterial populations. Our results showed that the method of application can be an essential element in determining the effects of the inoculant on plant growth. In fact, when applied as a maize seed treatment, B. ambifaria MCI 7 promoted plant growth significantly; on the contrary, when incorporated into soil, the same strain reduced plant growth markedly. As far as the bacterial community structure is concerned, B. ambifaria MCI 7 affected the indigenous microflora of treated plants according to the application method: seed treatment brought about an abrupt decrease in bacterial diversity, whereas incorporation into soil increased bacterial diversity. Moreover, changes in bacterial diversity were limited to r-strategist bacteria. In conclusion, B. ambifaria MCI 7 can act as both a plant growth-promoting rhizobacterium and a deleterious rhizobacterium depending on the inoculation method.
为了更好地了解不同接种方式的细菌接种剂对植物生长以及根际细菌种群群落结构的影响，通过种子黏附或混入土壤的方式，将洋葱伯克霍尔德菌MCI 7（原洋葱伯克霍尔德菌MCI 7）接种到玉米植株的根际。在不同接种浓度下评估植物生长情况。通过分析745株细菌分离株经聚合酶链反应（PCR）扩增的编码16S rRNA的DNA的限制性酶切图谱（ARDRA），评估根际细菌种群的群落结构。根据r/K策略的概念，为从对照植物和处理植物中分离出的每个细菌种群计算了一些多样性指数（丰富度、香农多样性、均匀度和平均遗传距离）。此外，应用分子方差分析（AMOVA）方法来估计不同细菌种群之间的遗传差异。我们的结果表明，接种方式可能是决定接种剂对植物生长影响的一个关键因素。事实上，当作为玉米种子处理剂使用时，洋葱伯克霍尔德菌MCI 7显著促进植物生长；相反，当混入土壤中时，同一菌株显著降低植物生长。就细菌群落结构而言，洋葱伯克霍尔德菌MCI 7根据接种方式影响处理植物的原生微生物群落：种子处理导致细菌多样性急剧下降，而混入土壤则增加细菌多样性。此外，细菌多样性的变化仅限于r策略细菌。总之，根据接种方法的不同，洋葱伯克霍尔德菌MCI 7既可以作为促进植物生长的根际细菌，也可以作为有害根际细菌。
