Microbial Mediation of Environmental Stresses: Nitrogen Fixation in the Spartina Alterniflora Rhizosphere

这个项目研究了固氮细菌的群落结构和环境特异性，这些细菌发生在从高产、低潮间带沼泽到高产、低生产力沼泽的整个梯度中。这种生产力的梯度反映在盐度、H2S浓度、pH和氧化还原电位的梯度上，所有这些都可能对固氮细菌产生影响。细菌反过来可能在氮的可用性上产生一个梯度，这可能会控制植物的生产力。该项目通过细菌DNA的PCR扩增和DNA“指纹”来表征沿着这一梯度的细菌群落。由此产生的带状模式提供了一种识别关键细菌种类和确定沿沼泽梯度的细菌群落组成的手段。人们正在研究关键细菌种类对环境胁迫的生理反应。研究人员还进行了细菌群落的互惠移植，以检查细菌和植物对新环境条件的反应。这项研究提高了我们确定非点源污染对盐沼微生物群落的影响以及这些群落变化对盐沼高等生物的影响的能力。研究结果在污染监测和环境风险评价中具有应用价值。

9407596 Lovell This project examines the community structure and environmental specificity of nitrogen-fixing bacteria that occur across the gradient from highly productive, low intertidal marsh to stressed, low-productivity, high marsh. This gradient in productivity is reflected in gradients in salinity, H2S concentration, pH, and redox potential, all of which have likely impact on the nitrogen-fixing bacteria. The bacteria in turn may generate a gradient in nitrogen availability, which may control plant productivity. The project characterizes the bacterial communities along this gradient by PCR amplification of the bacterial DNA and DNA "fingerprinting." The resulting banding patterns provide a means of identifying key bacterial species and determining the composition of bacterial communites along the marsh gradient. The physiological responses of key bacterial species to environmental stresses are being studied. The investigator is also conducting reciprocal transplants of bacterial communities to examine bacterial and plant responses to the new environmental conditions. This research improves our ability to determine the effect of non-point source pollution on salt-marsh microbial communities and the effects of changes in these communities on higher organisms in salt marshes. The results of this research has application in pollution monitoring and environmental risk assessment.