The objectives of this study were to characterize the genetic diversity and evaluate the ability to tolerate stress as well as to assess the symbiotic efficiency of bacteria from cowpea nodules in agricultural soils with different uses in the semiarid region of Bahia state (Brazil). Soil samples were collected from six crop lands and one from the pristine Caatinga biome. After a trap-host experiment, the bacteria were isolated and culturally characterized. Isolates with typical characteristics of Bradyrhizobium were subjected to the nodC symbiotic gene amplification and those positive were evaluated by 16S-23S IGS-RFLP. Twenty-seven isolates belonging to different genetic clusters were selected for 16S-23S IGS sequencing. In additions, the selected bacteria were characterized biochemically and symbiotically. Among 420 characterized isolates, approximately 60% (251 isolates) displayed typical Bradyrhizobium cultural features. A total of 161, out of 251 isolates, showed positive amplification of the nodC gene fragment. The IGS-RFLP profiles analysis generated 33 groups and 27 were selected for further analysis. The fertility of the soils influenced the distribution of the isolates in the IGS-RFLP clusters. The bacteria were assigned to two genera, Bradyrhizobium and Microvirga , with 26 and 1 representative bacteria, respectively. Some isolates were able to tolerate NaCl as well as acidic and alkaline pH. In addition, isolates showed the abilities to produce biofilm under stress and to produce indole compounds, as well as efficient nodulation and nitrogen fixation. The isolates displayed great genetic, biochemical, and symbiotic variability with promising biotechnological potential.

中文翻译：

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巴西半干旱地区不同农业系统土壤豇豆根瘤菌的分子、生理和共生特征

本研究的目的是表征遗传多样性并评估耐受压力的能力，以及评估来自巴伊亚州（巴西）半干旱地区不同用途的农业土壤中豇豆根瘤细菌的共生效率。土壤样品是从六块农田和一块来自原始卡廷加生物群落中收集的。在诱捕宿主实验后，细菌被分离出来并进行了培养表征。对具有慢生根瘤菌典型特征的菌株进行 nodC 共生基因扩增，阳性菌株通过 16S-23S IGS-RFLP 进行评价。选择属于不同遗传簇的 27 个分离株进行 16S-23S IGS 测序。此外，选定的细菌在生化和共生方面进行了表征。在 420 个特征分离株中，大约 60%（251 个分离株）表现出典型的慢生根瘤菌文化特征。在 251 个分离株中，共有 161 个显示 nodC 基因片段的阳性扩增。IGS-RFLP 谱分析产生了 33 个组，其中 27 个被选为进一步分析。土壤的肥力影响了 IGS-RFLP 簇中分离株的分布。细菌被分配到两个属，Bradyrhizobium 和 Microvirga，分别有 26 和 1 个代表性细菌。一些分离株能够耐受 NaCl 以及酸性和碱性 pH。此外，分离株显示出在压力下产生生物膜和产生吲哚化合物的能力，以及有效的结瘤和固氮能力。这些分离株显示出巨大的遗传、生化和共生变异性，具有良好的生物技术潜力。