Kan Jinjun, Suzuki Marcelino T, Wang Kui, Evans Sarah E, Chen Feng
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, MD 21202, USA.
Appl Environ Microbiol. 2007 Nov;73(21):6776-89. doi: 10.1128/AEM.00541-07. Epub 2007 Sep 7.
Compared to freshwater and the open ocean, less is known about bacterioplankton community structure and spatiotemporal dynamics in estuaries, particularly those with long residence times. The Chesapeake Bay is the largest estuary in the United States, but despite its ecological and economic significance, little is known about its microbial community composition. A rapid screening approach, ITS (internal transcribed spacer)-LH (length heterogeneity)-PCR, was used to screen six rRNA operon (16S rRNA-ITS-23S rRNA) clone libraries constructed from bacterioplankton collected in three distinct regions of the Chesapeake Bay over two seasons. The natural length variation of the 16S-23S rRNA gene ITS region, as well as the presence and location of tRNA-alanine coding regions within the ITS, was determined for 576 clones. Clones representing unique ITS-LH-PCR sizes were sequenced and identified. Dramatic shifts in bacterial composition (changes within subgroups or clades) were observed for the Alphaproteobacteria (Roseobacter clade, SAR11), Cyanobacteria (Synechococcus), and Actinobacteria, suggesting strong seasonal variation within these taxonomic groups. Despite large gradients in salinity and phytoplankton parameters, a remarkably homogeneous bacterioplankton community was observed in the bay in each season. Stronger seasonal, rather than spatial, variation of the bacterioplankton population was also supported by denaturing gradient gel electrophoresis and LH-PCR analyses, indicating that environmental parameters with stronger seasonal, rather than regional, dynamics, such as temperature, might determine bacterioplankton community composition in the Chesapeake Bay.
与淡水和开阔海洋相比，人们对河口尤其是那些停留时间较长的河口的浮游细菌群落结构和时空动态了解较少。切萨皮克湾是美国最大的河口，但尽管它具有生态和经济意义，人们对其微生物群落组成却知之甚少。一种快速筛选方法，即ITS（内转录间隔区）-LH（长度异质性）-PCR，被用于筛选六个rRNA操纵子（16S rRNA-ITS-23S rRNA）克隆文库，这些文库是由在切萨皮克湾三个不同区域两个季节采集的浮游细菌构建而成的。对576个克隆测定了16S-23S rRNA基因ITS区域的自然长度变异，以及ITS内tRNA-丙氨酸编码区域的存在和位置。对代表独特ITS-LH-PCR大小的克隆进行测序和鉴定。观察到α-变形菌纲（玫瑰杆菌属分支、SAR11）、蓝细菌（聚球藻属）和放线菌的细菌组成发生了显著变化（亚群或进化枝内的变化），这表明这些分类群内存在强烈的季节变化。尽管盐度和浮游植物参数存在很大梯度，但在每个季节的海湾中都观察到了一个非常均匀的浮游细菌群落。变性梯度凝胶电泳和LH-PCR分析也支持浮游细菌种群的季节变化强于空间变化，这表明温度等具有较强季节动态而非区域动态的环境参数可能决定切萨皮克湾浮游细菌的群落组成。
