Instituto de Biotecnología y Biología Molecular (IBBM), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, Calles 47 y 115, 1900 La Plata, Argentina.
Res Microbiol. 2013 Feb-Mar;164(2):136-44. doi: 10.1016/j.resmic.2012.10.014. Epub 2012 Oct 31.
Flagellar-driven bacterial motility is an important trait for colonization of natural environments. Bradyrhizobium japonicum is a soil species that possesses two different flagellar systems: one subpolar and the other lateral, each with a filament formed by a different set of flagellins. While synthesis of subpolar flagellins is constitutive, translation of lateral flagellins was detected in rhizobia grown with l-arabinose, but not with d-mannitol as sole carbon source, independently of whether bacteria were in liquid or semisolid medium. We characterized swarming of B. japonicum in semisolid medium and found that this motility was faster with l-arabinose than with d-mannitol. By using mutants with deletions in each flagellin set, we evaluated the contribution of each flagellum system to swarming in semisolid culture media, and in soil. Mutants devoid of either of the flagella were affected in swarming in culture media, with this impairment being stronger for mutants without lateral flagella. In sterile soil at 100% or 80% field capacity, flagellar-driven motility of mutants able to swim but impaired in swarming was similar to wild type, indicating that swimming was the predominant movement here.
鞭毛驱动的细菌运动性是其在自然环境中定殖的一个重要特征。根瘤菌是一种土壤物种，它拥有两种不同的鞭毛系统：一种是亚极生的，另一种是侧生的，每种鞭毛系统都由不同的一套鞭毛蛋白组成。虽然亚极生鞭毛蛋白的合成是组成型的，但在以 l-阿拉伯糖作为唯一碳源培养的根瘤菌中检测到了侧生鞭毛蛋白的翻译，但以 d-甘露醇作为唯一碳源时则没有，而不论细菌是在液体还是半固体培养基中生长。我们对根瘤菌在半固体培养基中的聚集行为进行了表征，发现与 d-甘露醇相比，l-阿拉伯糖能使这种运动性更快。通过使用缺失每种鞭毛蛋白的突变体，我们评估了每个鞭毛系统在半固体培养基中和土壤中对聚集的贡献。缺失任何一种鞭毛的突变体在培养基中的聚集能力都受到影响，而没有侧生鞭毛的突变体受到的影响更大。在 100%或 80%田间持水量的无菌土壤中，能够游动但聚集能力受损的突变体的鞭毛驱动运动性与野生型相似，表明在这种情况下游动是主要的运动方式。
