Rubin Melissa A, Leff Laura G
Department of Biological Sciences, Kent State University, Kent, OH 44242, USA.
Microb Ecol. 2007 Aug;54(2):374-83. doi: 10.1007/s00248-007-9209-2. Epub 2007 Feb 17.
Nitrogen and phosphorus additions from anthropogenic sources can alter the nutrient pool of aquatic systems, both through increased nutrient concentrations and changes in stoichiometry. Because bacteria are important in nutrient cycling and aquatic food webs, information about how nutrients affect bacterial communities enhances our understanding of how changes in nutrient concentrations and stoichiometry potentially affect aquatic ecosystems as a whole. In this study, bacterial communities were examined in biofilms from cobbles collected across seasons at three sites along the Mahoning River (Ohio) with differing levels of inorganic nutrient inputs. Members of the alpha-, beta-, and gamma-proteobacteria, the Cytophaga-Flavobacteria cluster, and the Domain Bacteria were enumerated using fluorescent in situ hybridization. Detrended canonical correspondence analysis (DCCA) revealed that stoichiometric ratios, especially the dissolved inorganic nitrogen (DIN):soluble reactive phosphorus (SRP) molar ratio (NO(2)/NO(3) + NH(4):soluble reactive phosphorus), were correlated with abundance of the various bacterial taxa. However, the patterns were complicated by correlations with single nutrient concentrations and seasonal changes in temperature. Seasonal cycles appeared to play an important role in structuring the community, as there were distinct winter communities and temperature was negatively correlated with abundance of both alpha-proteobacteria and Cytophaga-Flavobacteria. However, nutrients and stoichiometry also appeared to affect the community. Numbers of cells hybridizing the Domain Bacteria probe were correlated with the DOC:DIN ratio, the beta-proteobacteria had a negative correlation with soluble reactive phosphorus concentrations and a positive correlation with the DIN:SRP ratio, and the Cytophaga-Flavobacteria had a significant negative partial correlation with the DIN:SRP ratio. Abundances of the alpha- or gamma-proteobacteria were not directly correlated to nutrient concentrations or stoichiometry. It appears that nutrient stoichiometry may be an important factor structuring bacterial communities; however, it is one of many factors, such as temperature, that are interlinked and must be considered together when studying environmental bacteria.
来自人为源的氮和磷添加会改变水生系统的养分库，这既体现在养分浓度增加上，也体现在化学计量比的变化上。由于细菌在养分循环和水生食物网中很重要，了解养分如何影响细菌群落有助于我们理解养分浓度和化学计量比的变化如何潜在地影响整个水生生态系统。在本研究中，对沿着马霍宁河（俄亥俄州）三个不同无机养分输入水平的地点全年采集的鹅卵石上的生物膜中的细菌群落进行了检测。使用荧光原位杂交技术对α-、β-和γ-变形菌纲、噬纤维菌-黄杆菌类群以及细菌域的成员进行了计数。去趋势典范对应分析（DCCA）表明，化学计量比，尤其是溶解无机氮（DIN）：可溶性活性磷（SRP）的摩尔比（NO(2)/NO(3)+NH(4)：可溶性活性磷），与各种细菌类群的丰度相关。然而，这些模式因与单一养分浓度和温度的季节性变化的相关性而变得复杂。季节性循环似乎在构建群落方面发挥了重要作用，因为存在明显的冬季群落，并且温度与α-变形菌纲和噬纤维菌-黄杆菌的丰度呈负相关。然而，养分和化学计量比似乎也会影响群落。与细菌域探针杂交的细胞数量与DOC：DIN比相关，β-变形菌纲与可溶性活性磷浓度呈负相关，与DIN：SRP比呈正相关，噬纤维菌-黄杆菌与DIN：SRP比具有显著的负偏相关。α-或γ-变形菌纲的丰度与养分浓度或化学计量比没有直接相关性。看来养分化学计量比可能是构建细菌群落的一个重要因素；然而，它只是众多相互关联的因素之一，例如温度，在研究环境细菌时必须综合考虑这些因素。
