Abstract—

Azospirillum brasilense forms biofilms on various surfaces. It was previously shown that inactivation of the ahpC gene of alkyl hydroperoxide reductase in the SK586 mutant of A. brasilense Sp245 led to an increased sensitivity to peroxides and to changes in flagellation, motility, and cell surface properties. This work revealed that under nitrogen limitation, Sp245 switches predominantly to the biofilm mode of life, whereas this tendency is not characteristic of the mutant SK586. Inactivation of the ahpC gene negatively affects the viability of SK586 in biofilms, which is most noticeable under nitrogen limitation. While no significant morphological differences were found between cyst-like forms of Sp245 and SK586, the dormant mutant forms grown in a nitrogen-free medium were more sensitive to hydrogen peroxide than the dormant forms of Sp245. In Sp245 biofilms, viable forms resistant to drying were found even after 9 months of storage, while in SK586 biofilms, such bacteria remained viable for less than a month. In the course of adaptation to the plant root system, the number of Azospirillum cells resistant to drying increased, as compared to the number of such cells from mature biofilms on abiotic surfaces. Unlike Sp245, SK586 did not promote the development of the root system and the growth of the aerial parts of 10-day-old plants, possibly owing to its lower ability to colonize the roots of wheat seedlings incubated in a liquid medium. Alkyl hydroperoxide reductase is probably essential for better resistance of azospirilla to various stresses and for manifestation of their plant-growth-promoting activity.

中文翻译：

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抑制了巴西螺旋藻ahpC突变体中生物膜的形成效率，降低了其对氧化应激和干燥的生物膜抗性。

摘要—

巴西固氮螺菌在各种表面上形成生物膜。先前已证明，巴西拟南芥Sp245的SK586突变体中烷基氢过氧化物还原酶ahpC基因的失活导致对过氧化物的敏感性增加，并导致鞭毛，运动性和细胞表面特性发生变化。这项工作表明，在氮限制下，Sp245主要转换为生物膜的生命模式，而这种趋势并不是突变体SK586的特征。ahpC的失活基因对生物膜中SK586的生存能力产生负面影响，这在氮限制下最为明显。虽然在Sp245和SK586的囊状形式之间没有发现明显的形态学差异，但是在无氮培养基中生长的休眠突变体形式比Sp245的休眠形式对过氧化氢更为敏感。在Sp245生物膜中，即使保存了9个月也发现了耐干燥的存活形式，而在SK586生物膜中，这种细菌仍存活了不到一个月的时间。在适应植物根系的过程中，固氮螺菌的数量与来自非生物表面上成熟生物膜的此类细胞的数量相比，具有抗干燥性的细胞有所增加。与Sp245不同，SK586不能促进10天龄植物的根系发育和地上部分的生长，这可能是由于其在液体培养基中培养的小麦幼苗的根部定植能力较低。烷基氢过氧化物还原酶可能对于使偶氮螺旋藻更好地抵抗各种胁迫并体现其促进植物生长的活性可能是必不可少的。