Evaluating the genetic and functional diversity of major microorganisms in nitrogen-fixing sugar cane-microbe communities

尽管氮的供应对生态系统的功能至关重要，但许多自然环境中重要的固氮生物的信息仍然非常少，因为大多数细菌无法培养。nifH mRNA的直接靶向是选择的工具，以确定主要固氮生物的栖息地中的主要固氮生物是inconscious。虽然甘蔗显示出高的输入从生物固氮（BNF），目前的数据的基础上培养固氮菌从甘蔗plants不能解释it. Further，大多数活性位点和固氮菌没有得到很好的表征，没有培养的偏见。因此，将采用非培养物依赖性方法。NifH mRNA水平估计在不同部位的根和芽的甘蔗品种，已知得到大量或几乎可以忽略不计的输入生物固氮。为了从最具活性的固氮细菌中获得nifH序列，构建了nifH克隆文库，并通过对具有最高nifH表达水平的植物组织进行比较序列分析来评估。这些数据将用于微阵列和DGGE分析的DNA/mRNA谱分析。这些分析研究旨在检测在固氮中非常活跃的稳定微生物群落，并旨在评估不同土壤类型和氮肥对其的影响。

Despite the crucial importance of nitrogen availability on the functioning of ecosystems, information on important diazotrophs in many natural environments is still very poor, since most bacteria defy cultivation. Direct targeting of nifH mRNA is the tool of choice to identify primary N2-fixing organisms in habitats where major diazotrophs are inconspicious. Although sugar cane shows a high input from biological N2 fixation (BNF), current data based on cultivated diazotrophic bacteria from sugar cane plants cannot explain it. Furthermore, most active sites and diazotrophs are not well characterized without the bias of cultivation. Therefore, culture-independent methods will be applied. NifH mRNA levels are estimated in different parts of roots and shoots of cane varieties which are known to get large or almost negligible inputs by BNF. To obtain nifH sequences from the most active N2-fixing bacteria, nifH clone libraries are constructed and evaluated by comparative sequence analyses from plant tissues having the highest nifH expression levels. These data will be used for DNA/mRNA profiling with microarrays and DGGE analyses. These profiling studies aim to detect stable microbial communities which are very active in nitrogen fixation, and aim to assess the influence of different soil types and N-fertilization on them.