Bezzate S, Aymerich S, Chambert R, Czarnes S, Berge O, Heulin T
Génétique Molé culaire et Cellulaire, INRA and CNRS, URA1925, Thiverval-Grignon, France.
Environ Microbiol. 2000 Jun;2(3):333-42. doi: 10.1046/j.1462-2920.2000.00114.x.
Inoculation of wheat roots with Paenibacillus (formerly Bacillus) polymyxa CF43 increases the mass of root-adhering soil. We tested the role of levan, a fructosyl polymer produced by strain CF43, in the aggregation of soil adhering to wheat roots. The P. polymyxa gene homologous to the Bacillus subtilis sacB gene encoding levansucrase was cloned and sequenced. The corresponding gene product synthesises high molecular weight levan. A P. polymyxa mutant strain, SB03, whose sacB gene is disrupted, was constructed using heterogramic conjugation. Effects of wheat inoculation with the wild type and the mutant strain were compared using two different cultivated silt loam soils in four independent pot experiments. Roots of wheat plantlets inoculated with CF43 or SB03 were colonized after 7-14 days at the same level, and root and shoot masses were not significantly different from those of the non-inoculated control plants. The ratio of root-adhering soil dry mass to root tissue dry mass was significantly higher for plants inoculated with strain CF43 than for those inoculated with mutant strain SB03: +30% in Orgeval soil and +100% in Dieulouard soil. Thus the levan produced by P. polymyxa is implicated in the aggregation of root-adhering soil on wheat.
用多粘类芽孢杆菌（以前称为芽孢杆菌）CF43接种小麦根系可增加根际土壤的质量。我们测试了由CF43菌株产生的果聚糖聚合物左聚糖在附着于小麦根系的土壤团聚中的作用。克隆并测序了与枯草芽孢杆菌编码蔗糖酶的sacB基因同源的多粘类芽孢杆菌基因。相应的基因产物合成高分子量左聚糖。利用异源接合构建了sacB基因被破坏的多粘类芽孢杆菌突变株SB03。在四个独立的盆栽试验中，使用两种不同的耕作粉质壤土比较了野生型和突变株接种小麦的效果。接种CF43或SB03的小麦幼苗根系在7-14天后定殖水平相同，根和地上部分的质量与未接种的对照植株没有显著差异。接种CF43菌株的植株，其根际土壤干质量与根组织干质量的比值显著高于接种突变株SB03的植株：在奥尔热瓦尔土壤中高30%，在迪厄卢阿尔德土壤中高100%。因此，多粘类芽孢杆菌产生的左聚糖与小麦根际土壤的团聚有关。
