MARC PREDOCTORAL FELLOWSHIP

马克博士前奖学金

• 批准号: 6518819
• 负责人: DORIS A BETANCOURT
• 金额: $ 1.76万
• 依托单位: NORTH CAROLINA STATE UNIVERSITY RALEIGH
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-01 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6518819
• 关键词: Rhizobiaceae; enzyme activity; molecular genetics; molybdenum; nitrogen fixation; nitrogenase; nucleic acid sequence; polymerase chain reaction; ribosomal RNA; water environment; water microbiology

We have recently isolated nitrogen-fix nitrogen-fixing bacteria that have molybdenum-independent nitrogenases from natural environments (waste water treatment plants, ponds, streams, and salt marshes) using molybdenum (Mo)- and nitrogen-free enrichment media. We hypothesize that non-molybdenum nitrogenases are important under natural conditions even in the presence of ordinarily sufficient molybdenum because micro environments devoid of Mo may be created by removal of Mo by the microorganisms themselves and by other organisms such as plants. We propose to extend our survey to rhizospheres and rhizoplanes of C4 plants such as sugarcane, corn, and spartina grass (in salt marshes) where conditions should favor creation of Mo-deficient micro niches. Nitrogen-fixing bacteria isolated the rhizosphere and rhizoplane of plants will be phylogenetically characterized using 16S rRNA sequences and the presence or absence of alternative nitrogenase systems will be determined using PCR primers specific for amplification of genes specific for each nitrogenase system. Representive strains will be further characterized with respect to nitrogen fixation capabilities and ability to colonize the rhizosphere and rhizoplane of plants. To our knowledge the use of Mo-deficient enrichment media have not been used to isolate diazotrophs directly from these environments. Thus, it can be expected that diazotrophs with novel properties will be identified during this study. The intent of the proposed study is to further our understanding of why certain diazotrophic organisms have Mo-independent nitrogenases and the role that these nitrogenases might play in the global nitrogen cycle.

我们最近使用无钼 (Mo) 和无氮富集培养基从自然环境（废水处理厂、池塘、溪流和盐沼）中分离出了具有不依赖于钼的固氮酶的固氮细菌。 我们假设非钼固氮酶在自然条件下甚至在通常充足的钼存在下也很重要，因为没有钼的微环境可能是通过微生物本身和其他生物体（例如植物）去除钼而产生的。我们建议将我们的调查范围扩大到甘蔗、玉米和米草（盐沼中）等 C4 植物的根际和根面，这些地方的条件有利于形成缺钼的微生态位。 从植物根际和根面分离的固氮细菌将使用 16S rRNA 序列进行系统发育表征，并使用对每种固氮酶系统特异基因进行扩增的 PCR 引物来确定是否存在替代固氮酶系统。 将进一步表征代表性菌株的固氮能力以及在植物根际和根面定殖的能力。 据我们所知，缺钼富集培养基尚未用于直接从这些环境中分离固氮菌。 因此，可以预期在这项研究中将鉴定出具有新特性的固氮菌。这项研究的目的是进一步了解为什么某些固氮生物具有不依赖钼的固氮酶以及这些固氮酶在全球氮循环中可能发挥的作用。