Waidner Lisa A, Kirchman David L
University of Delaware, College of Marine and Earth Studies, 700 Pilottown Road, Lewes, DE 19958, USA.
Appl Environ Microbiol. 2008 Jul;74(13):4012-21. doi: 10.1128/AEM.02324-07. Epub 2008 May 9.
The diversity of aerobic anoxygenic phototrophic (AAP) bacteria has been examined in marine habitats, but the types of AAP bacteria in estuarine waters and distribution of ecotypes in any environment are not well known. The goal of this study was to determine the diversity of AAP bacteria in the Delaware estuary and to examine the distribution of select ecotypes using quantitative PCR (qPCR) assays for the pufM gene, which encodes a protein in the light reaction center of AAP bacteria. In PCR libraries from the Delaware River, pufM genes similar to those from Beta- (Rhodoferax-like) or Gammaproteobacteria comprised at least 50% of the clones, but the expressed pufM genes from the river were not dominated by these two groups in August 2002 (less than 31% of clones). In four transects, qPCR data indicated that the gammaproteobacterial type of pufM was abundant only near the mouth of the bay whereas Rhodoferax-like AAP bacteria were restricted to waters with a salinity of <5. In contrast, a Rhodobacter-like pufM gene was ubiquitous, but its distribution along the salinity gradient varied with the season. High fractions (12 to 24%) of all three pufM types were associated with particles. The data suggest that different groups of AAP bacteria are controlled by different environmental factors, which may explain current difficulties in predicting the distribution of total AAP bacteria in aquatic environments.
需氧不产氧光合细菌(AAP细菌)的多样性已在海洋栖息地中得到研究,但河口水中AAP细菌的类型以及任何环境中生态型的分布情况尚不清楚。本研究的目的是确定特拉华河口AAP细菌的多样性,并使用针对pufM基因的定量PCR(qPCR)检测方法来研究特定生态型的分布,pufM基因编码AAP细菌光反应中心的一种蛋白质。在特拉华河的PCR文库中,与β-(类红环菌属)或γ-变形菌纲相似的pufM基因至少占克隆的50%,但2002年8月该河中表达的pufM基因并非由这两组主导(克隆占比不到31%)。在四个断面中,qPCR数据表明,pufM的γ-变形菌纲类型仅在海湾口附近丰富,而类红环菌属的AAP细菌局限于盐度<5的水域。相比之下,类红杆菌属的pufM基因普遍存在,但其沿盐度梯度的分布随季节变化。所有三种pufM类型的高比例(12%至24%)与颗粒相关。数据表明,不同组的AAP细菌受不同环境因素控制,这可能解释了目前在预测水生环境中总AAP细菌分布方面存在的困难。