Straub K L, Buchholz-Cleven B E
Max-Planck-Institut für Marine Mikrobiologie, 28359 Bremen, Germany.
Appl Environ Microbiol. 1998 Dec;64(12):4846-56. doi: 10.1128/AEM.64.12.4846-4856.1998.
Anaerobic, nitrate-dependent microbial oxidation of ferrous iron was recently recognized as a new type of metabolism. In order to study the occurrence of three novel groups of ferrous iron-oxidizing, nitrate-reducing bacteria (represented by strains BrG1, BrG2, and BrG3), 16S rRNA-targeted oligonucleotide probes were developed. In pure-culture experiments, these probes were shown to be suitable for fluorescent in situ hybridization, as well as for hybridization analysis of denaturing gradient gel electrophoresis (DGGE) patterns. However, neither enumeration by in situ hybridization nor detection by the DGGE-hybridization approach was feasible with sediment samples. Therefore, the DGGE-hybridization approach was combined with microbiological methods. Freshwater sediment samples from different European locations were used for enrichment cultures and most-probable-number (MPN) determinations. Bacteria with the ability to oxidize ferrous iron under nitrate-reducing conditions were detected in all of the sediment samples investigated. At least one of the previously described types of bacteria was detected in each enrichment culture. MPN studies showed that sediments contained from 1 x 10(5) to 5 x 10(8) ferrous iron-oxidizing, nitrate-reducing bacteria per g (dry weight) of sediment, which accounted for at most 0.8% of the nitrate-reducing bacteria growing with acetate. Type BrG1, BrG2, and BrG3 bacteria accounted for an even smaller fraction (0.2% or less) of the ferrous iron-oxidizing, nitrate-reducing community. The DGGE patterns of MPN cultures suggested that more organisms than those isolated thus far are able to oxidize ferrous iron with nitrate. A comparison showed that among the anoxygenic phototrophic bacteria, organisms that have the ability to oxidize ferrous iron also account for only a minor fraction of the population.
亚铁的厌氧、硝酸盐依赖型微生物氧化作用最近被确认为一种新型代谢类型。为了研究三类新型亚铁氧化、硝酸盐还原细菌（以菌株BrG1、BrG2和BrG3为代表）的存在情况，开发了针对16S rRNA的寡核苷酸探针。在纯培养实验中，这些探针被证明适用于荧光原位杂交以及变性梯度凝胶电泳（DGGE）图谱的杂交分析。然而，对于沉积物样品，无论是通过原位杂交进行计数还是通过DGGE杂交方法进行检测都不可行。因此，将DGGE杂交方法与微生物学方法相结合。来自欧洲不同地点的淡水沉积物样品用于富集培养和最大可能数（MPN）测定。在所研究的所有沉积物样品中都检测到了在硝酸盐还原条件下具有氧化亚铁能力的细菌。在每个富集培养物中至少检测到一种先前描述的细菌类型。MPN研究表明，沉积物中每克（干重）含有1×10⁵至5×10⁸个氧化亚铁、硝酸盐还原细菌，这些细菌最多占以乙酸盐生长的硝酸盐还原细菌的0.8%。BrG1、BrG2和BrG3型细菌在氧化亚铁、硝酸盐还原群落中所占比例甚至更小（0.2%或更低）。MPN培养物的DGGE图谱表明，能够利用硝酸盐氧化亚铁的生物比迄今分离出的生物更多。一项比较表明，在无氧光合细菌中，具有氧化亚铁能力的生物在种群中也只占一小部分。
