Azospirillum brasilense Az19 is a plant-beneficial bacterium capable of protecting plants from the negative effects of drought. The objective of this study was to determine and analyze the genomic sequence of strain Az19 as a means of identifying putative stress-adaptation mechanisms. A high-quality draft genome of ca. 7 Mb with a predicted coding potential of 6710 genes was obtained. Phylogenomic analyses confirmed that Az19 belongs to the brasilense clade and is closely related to strains Az39 and REC3. Functional genomics revealed that the denitrification pathway of Az19 is incomplete, which was in agreement with a reduced growth on nitrate under low O₂ concentrations. Putative genes of the general stress response and oxidative stress-tolerance, as well as synthesis of exopolysaccharides, carotenoids, polyamines and several osmolytes, were detected. An additional poly-beta-hydroxybutyrate (PHB) synthase coding gene was found in Az19 genome, but the accumulation of PHB did not increase under salinity. The detection of exclusive genes related to DNA repair led to discover that strain Az19 also has improved UV-tolerance, both in vitro and in planta. Finally, the analysis revealed the presence of multiple kaiC-like genes, which could be involved in stress-tolerance and, possibly, light responsiveness. Although A. brasilense has been a model for the study of beneficial plant-associated rhizobacteria, the evidence collected in this current study suggests, for the first time in this bacterial group, an unexpected possibility of adaptation to the phyllosphere.

巴西固氮螺菌Az19是一种植物有益细菌，能够保护植物免受干旱的不利影响。这项研究的目的是确定和分析菌株Az19的基因组序列，作为鉴定假定的应力适应机制的一种手段。大约一个高质量的基因组草图。获得7 Mb，具有预测的6710个基因的编码潜力。系统生物学分析证实，Az19属于巴西进化枝，并且与菌株Az39和REC3密切相关。功能基因组学表明，Az19的反硝化途径不完全，这与低O ₂下硝酸盐的生长减少有关浓度。检测到一般应激反应和氧化应激耐受性的推定基因，以及外多糖，类胡萝卜素，多胺和几种渗透压的合成。在Az19基因组中发现了另一个聚β-羟基丁酸（PHB）合酶编码基因，但在盐度下PHB的积累并未增加。对与DNA修复相关的排他性基因的检测导致发现，Az19菌株在体外和植物体内均具有改善的紫外线耐受性。最后，分析揭示了多个kaiC样基因的存在，这些基因可能与胁迫耐受性以及可能的光响应性有关。虽然巴西sil 作为研究有益的植物相关根际细菌的模型，本次研究收集的证据首次表明，在该细菌群中，有一种意料之外的适应叶环的可能性。