Azoarcus grass endophytes contribute fixed nitrogen to the plant in an unculturable state
Azoarcus grass endophytes contribute fixed nitrogen to the plant in an unculturable state
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DOI：
10.1094/mpmi.2002.15.3.233
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发表时间：
2002-03-01
影响因子：
3.5
通讯作者：
Piché, Y
中科院分区：
文献类型：
--
作者：
Hurek, T;Handley, LL;Piché, Y
通过评价生长在温室中的接种植物和取自自然环境的未接种植物，评估了在卡拉草根际中的固氮细菌内生菌Azoarcus sp.菌株BH 72可以为植物提供固定氮的程度。接种物由野生型细菌或nifK（-）突变株BHNKD 4组成。在N-2缺乏条件下，接种菌株BH 72的植物（N2固定测试植物）在8个月后比接种突变菌株的植物（非N-2固定对照植物）生长更好并且积累更多的氮，具有更低的σ（15）N特征。多聚腺苷酸化或聚合酶链反应扩增的BH 72 nifH转录本从测试中检索，但不是从对照植物。BH 72 nifH转录本丰富。接种物无法重新分离。这些结果表明，固氮菌BH 72在不可培养状态下可以为植物提供结合态N-2。从自然环境中采集的未接种植物中也检测到丰富的BH 72 nifH转录本，从其中也不能分离出Azoarcus sp. BH 72。固氮酶基因转录的定量分析表明菌株BH 72具有很高的生物固氮潜力。固氮酶序列的系统发育分析预测，未培养的禾本科内生菌，包括固氮菌属。在天然草地生态系统中具有生态优势，并在固氮中发挥重要作用。
The extent to which the N-2-fixing bacterial endophyte Azoarcus sp. strain BH72 in the rhizosphere of Kallar grass can provide fixed nitrogen to the plant was assessed by evaluating inoculated plants grown in the greenhouse and uninoculated plants taken from the natural environment. The inoculum consisted of either wild-type bacteria or nifK(-) mutant strain BHNKD4. In N-2-deficient conditions, plants inoculated with strain BH72 (N2-fixing test plants) grew better and accumulated more nitrogen with a lower sigma(15)N signature after 8 months than did plants inoculated with the mutant strain (non-N-2-rixing control plants). Polyadenylated or polymerase chain reaction-amplified BH72 nifH transcripts were retrieved from test but not from control plants. BH72 nifH transcripts were abundant. The inocula could not be reisolated. These results indicate that Azoarcus sp. BH72 can contribute combined N-2 to the plant in an unculturable state. Abundant BH72 nifH transcripts were detected also in uninoculated plants taken from the natural environment, from which Azoarcus sp. BH72 also could not be isolated. Quantification of nitrogenase gene transcription indicated a high potential of strain BH72 for biological N2, fixation in association with roots. Phylogenetic analysis of nitrogenase sequences predicted that uncultured grass endophytes including Azoarcus spp. are ecologically dominant and play an important role in N-2-fixation in natural grass ecosystems.