Coelho Marcia Reed Rodrigues, de Vos Marjon, Carneiro Newton Portilho, Marriel Ivanildo Evódio, Paiva Edilson, Seldin Lucy
Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
FEMS Microbiol Lett. 2008 Feb;279(1):15-22. doi: 10.1111/j.1574-6968.2007.00975.x. Epub 2007 Dec 7.
The diversity of nitrogen-fixing bacteria was assessed in the rhizospheres of two cultivars of sorghum (IS 5322-C and IPA 1011) sown in Cerrado soil amended with two levels of nitrogen fertilizer (12 and 120 kg ha(-1)). The nifH gene was amplified directly from DNA extracted from the rhizospheres, and the PCR products cloned and sequenced. Four clone libraries were generated from the nifH fragments and 245 sequences were obtained. Most of the clones (57%) were closely related to nifH genes of uncultured bacteria. NifH clones affiliated with Azohydromonas spp., Ideonella sp., Rhizobium etli and Bradyrhizobium sp. were found in all libraries. Sequences affiliated with Delftia tsuruhatensis were found in the rhizosphere of both cultivars sown with high levels of nitrogen, while clones affiliated with Methylocystis sp. were detected only in plants sown under low levels of nitrogen. Moreover, clones affiliated with Paenibacillus durus could be found in libraries from the cultivar IS 5322-C sown either in high or low amounts of fertilizer. This study showed that the amount of nitrogen used for fertilization is the overriding determinative factor that influenced the nitrogen-fixing community structures in sorghum rhizospheres cultivated in Cerrado soil.
在施用两种氮肥水平（12和120千克公顷⁻¹）的塞拉多土壤中播种的两个高粱品种（IS 5322-C和IPA 1011）的根际中，评估了固氮细菌的多样性。从根际提取的DNA中直接扩增nifH基因，并对PCR产物进行克隆和测序。从nifH片段生成了四个克隆文库，获得了245个序列。大多数克隆（57%）与未培养细菌的nifH基因密切相关。在所有文库中都发现了与偶氮氢单胞菌属、艾氏菌属、费氏中华根瘤菌和慢生根瘤菌属相关的NifH克隆。在高氮水平播种的两个品种的根际中都发现了与鹤见德尔夫特菌相关的序列，而与甲基孢囊菌属相关的克隆仅在低氮水平播种的植物中检测到。此外，在高肥或低肥播种的品种IS 5322-C的文库中都可以发现与硬壁芽孢杆菌相关的克隆。这项研究表明，施肥所用的氮量是影响塞拉多土壤中种植的高粱根际固氮群落结构的首要决定性因素。
