Biodiversity Research Center, Academia Sinica, No. 128 Academia Rd., Sec. 2, Nankang, Taipei, 115, Taiwan.
Microb Ecol. 2012 Jan;63(1):224-37. doi: 10.1007/s00248-011-9912-x. Epub 2011 Jul 23.
Sulfate- and sulfite-reducing prokaryotes (SSRP) communities play a key role in both sulfur and carbon cycles. In estuarine ecosystems, sulfate concentrations change with tides and could be limited in tidal freshwater reach or deep sediments. In a subtropical estuary of northern Taiwan in December 2007, we examined the compositional changes of SSRP communities. We examined three sites: from the lower estuarine brackish-water reach (site GR and mangrove vegetation site, GM) to the upper estuarine tidal freshwater reach (site HR), as well as from surface to a 50-cm depth. The partial sequence of sulfite reductase (dsrB) genes was used as a molecular marker of SSRP, linked to polymerase chain reaction and denaturing gradient gel electrophoresis (DGGE) techniques. SSRP communities of the DGGE profiles varied with sites according to one-way analyses of similarities (Global R = 0.69, P = 0.001). Using cluster analysis, the DGGE profile was found to show site-specific clusters and a distinct depth zonation (five, six, and two SSRP communities at the GM, GR, and HR sites, respectively). SSRP composition was highly correlated to the combination of salinity, reduced sulfur, and total organic carbon contents (BIO-ENV analysis, r ( s ) = 0.56). After analyzing a total of 35 dsrB sequences in the DGGE gel, six groups with 15 phylotypes were found, which were closely related to marine-freshwater gradient. Moreover, sequences neighboring sulfite-reducing prokaryotes were observed, in addition to those affiliated to sulfate-reducing prokaryotes. Four phylotypes harvested in HR resembled the genus Desulfitobacterium, a sulfite-reducing prokaryote, which failed to use sulfate as an electron acceptor and were active in freshwater and sulfate-limited habitat. The other five phylotypes in the HR reach belonged to the sulfate-reducing prokaryotes of the genera Desulfatiferula, Desulfosarcina, Desulfovibrio, and Desulfotomaculum, which appeared to tolerate low salinity and low sulfate supply. SSRP phylotypes at the mangrove-vegetated GM site (five phylotypes in two groups) were phylogenetically less diverse, when compared with those at the non-mangrove-vegetated GR site (three phylotypes in three groups) and the tidally influenced freshwater HR site (nine phylotypes in five groups). Phylotypes found at GR and GM were all affiliated to marine sulfate-reducing prokaryote strains of the genera Desulfofaba, Desulfobotulus, Desulfatiferula, Desulfosarcina, and Desulfotomaculum. Notably, a phylotype recorded in the surface sediment at GR resembled the genus Desulfobulbus, which was recorded from freshwater environment consisting of the freshwater input at GR during ebb tides.
硫酸盐-和亚硫酸盐还原菌（SSRP）群落在硫和碳循环中起着关键作用。在河口生态系统中，硫酸盐浓度随潮汐而变化，在潮汐淡水区或深部沉积物中可能受到限制。2007 年 12 月，在中国台湾北部的一个亚热带河口，我们研究了 SSRP 群落的组成变化。我们考察了三个地点：从下游河口咸水区域（GR 点和红树林植被点，GM 点）到上游河口潮汐淡水区域（HR 点），以及从表层到 50 厘米深度。亚硫酸盐还原酶（dsrB）基因的部分序列被用作 SSRP 的分子标记，与聚合酶链反应和变性梯度凝胶电泳（DGGE）技术结合使用。根据相似性的单向分析（全局 R = 0.69，P = 0.001），DGGE 图谱的 SSRP 群落随地点而变化。通过聚类分析，发现 DGGE 图谱显示出特定于地点的聚类和明显的深度分区（GM、GR 和 HR 点分别有五个、六个和两个 SSRP 群落）。SSRP 组成与盐度、还原态硫和总有机碳含量的组合高度相关（BIO-ENV 分析，r（s）= 0.56）。在对 DGGE 凝胶中的 35 个 dsrB 序列进行分析后，发现了 6 个组，有 15 个系统发育型，与海洋-淡水梯度密切相关。此外，除了与硫酸盐还原菌有关的序列外，还观察到与亚硫酸盐还原菌相邻的序列。在 HR 处采集的 4 个系统发育型类似于亚硫酸盐还原菌属 Desulfitobacterium，它不能将硫酸盐用作电子受体，并且在淡水和硫酸盐受限的生境中活跃。HR 处的其他 5 个系统发育型属于硫酸盐还原菌属 Desulfatiferula、Desulfosarcina、Desulfovibrio 和 Desulfotomaculum，它们似乎能耐受低盐度和低硫酸盐供应。与非红树林植被 GR 点（三个组中的三个系统发育型）和受潮汐影响的淡水 HR 点（五个组中的九个系统发育型）相比，红树林植被 GM 点的 SSRP 系统发育型（两个组中的五个系统发育型）在系统发育上多样性较低。在 GR 和 GM 处发现的系统发育型均与海洋硫酸盐还原菌属 Desulfofaba、Desulfobotulus、Desulfatiferula、Desulfosarcina 和 Desulfotomaculum 的菌株有关。值得注意的是，在 GR 表层沉积物中记录的一个系统发育型类似于 Desulfobulbus 属，该属记录于由 GR 退潮时淡水输入组成的淡水环境中。
