Ramsing N B, Fossing H, Ferdelman T G, Andersen F, Thamdrup B
Max Planck Institute for Marine Microbiology, Bremen, Germany.
Appl Environ Microbiol. 1996 Apr;62(4):1391-404. doi: 10.1128/aem.62.4.1391-1404.1996.
The vertical distribution of major and intermediate electron acceptors and donors was measured in a shallow stratified fjord. Peaks of zero valence sulfur, Mn(IV), and Fe(III) were observed in the chemocline separating oxic surface waters from sulfidic and anoxic bottom waters. The vertical fluxes of electron acceptors and donors (principally O2 and H2S) balanced within 5%; however, the zones of oxygen reduction and sulfide oxidation were clearly separated. The pathway of electron transfer between O2 and H2S was not apparent from the distribution of sulfur, nitrogen, or metal compounds investigated. The chemical zonation was related to bacterial populations as detected by ethidium bromide (EtBr) staining and by in situ hybridization with fluorescent oligonucleotide probes of increasing specificity. About half of all EtBr-stained cells were detectable with a general oligonucleotide probe for all eubacteria when digital image analysis algorithms were used to improve sensitivity. Both EtBr staining and hybridization indicated a surprisingly uniform distribution of bacteria throughout the water column. However, the average cell size and staining intensity as well as the abundance of different morphotypes changed markedly within the chemocline. The constant overall cell counts thus concealed pronounced population shifts within the water column. Cells stained with a delta 385 probe (presumably sulfate-reducing bacteria) were detected at the chemocline at about 5 x 10(4) cells per ml, and this concentration increased to 2 x 10(5) cells per ml beneath the chemocline. A long slim rod-shaped bacterium was found in large numbers in the oxic part of the chemocline, whereas large ellipsoid cells dominated at greater depth. Application of selective probes for known genera of sulfate-reducing bacteria gave only low cell counts, and thus it was not possible to identify the dominant morphotypes of the sulfate-reducing community.
在一个浅水层化峡湾中测量了主要和中间电子受体及供体的垂直分布。在将含氧表层水与含硫和缺氧底层水分开的化学跃层中观察到了零价硫、锰（IV）和铁（III）的峰值。电子受体和供体（主要是氧气和硫化氢）的垂直通量在5%的范围内平衡；然而，氧还原区和硫化物氧化区明显分开。从所研究的硫、氮或金属化合物的分布来看，氧气和硫化氢之间的电子转移途径并不明显。化学分区与通过溴化乙锭（EtBr）染色以及与特异性不断增加的荧光寡核苷酸探针进行原位杂交检测到的细菌种群有关。当使用数字图像分析算法提高灵敏度时，用针对所有真细菌的通用寡核苷酸探针可检测到约一半的EtBr染色细胞。EtBr染色和杂交均表明整个水柱中细菌分布惊人地均匀。然而，在化学跃层内，平均细胞大小、染色强度以及不同形态类型的丰度发生了明显变化。因此，细胞总数恒定掩盖了水柱内明显的种群变化。用δ385探针染色的细胞（可能是硫酸盐还原菌）在化学跃层中被检测到，浓度约为每毫升5×10⁴个细胞，在化学跃层以下该浓度增加到每毫升2×10⁵个细胞。在化学跃层的含氧部分发现了大量细长杆状细菌，而在更深的深度则以大型椭圆形细胞为主。应用针对已知硫酸盐还原菌属的选择性探针得到的细胞计数很低，因此无法确定硫酸盐还原菌群的主要形态类型。
