Hugenholtz P, Tyson G W, Webb R I, Wagner A M, Blackall L L
Advanced Wastewater Management Centre, Department of Microbiology and Parasitology, The University of Queensland, Brisbane 4072, Australia.
Appl Environ Microbiol. 2001 Jan;67(1):411-9. doi: 10.1128/AEM.67.1.411-419.2001.
A molecular approach was used to investigate a recently described candidate division of the domain Bacteria, TM7, currently known only from environmental 16S ribosomal DNA sequence data. A number of TM7-specific primers and probes were designed and evaluated. Fluorescence in situ hybridization (FISH) of a laboratory scale bioreactor using two independent TM7-specific probes revealed a conspicuous sheathed-filament morphotype, fortuitously enriched in the reactor. Morphologically, the filament matched the description of the Eikelboom morphotype 0041-0675 widely associated with bulking problems in activated-sludge wastewater treatment systems. Transmission electron microscopy of the bioreactor sludge demonstrated that the sheathed-filament morphotype had a typical gram-positive cell envelope ultrastructure. Therefore, TM7 is only the third bacterial lineage recognized to have gram-positive representatives. TM7-specific FISH analysis of two full-scale wastewater treatment plant sludges, including the one used to seed the laboratory scale reactor, indicated the presence of a number of morphotypes, including sheathed filaments. TM7-specific PCR clone libraries prepared from the two full-scale sludges yielded 23 novel TM7 sequences. Three subdivisions could be defined based on these data and publicly available sequences. Environmental sequence data and TM7-specific FISH analysis indicate that members of the TM7 division are present in a variety of terrestrial, aquatic, and clinical habitats. A highly atypical base substitution (Escherichia coli position 912; C to U) for bacterial 16S rRNAs was present in almost all TM7 sequences, suggesting that TM7 bacteria, like Archaea, may be streptomycin resistant at the ribosome level.
采用分子方法研究细菌域中一个最近描述的候选类群TM7，目前仅从环境16S核糖体DNA序列数据中得知该类群。设计并评估了许多TM7特异性引物和探针。使用两种独立的TM7特异性探针，对实验室规模的生物反应器进行荧光原位杂交（FISH），结果显示出一种明显的鞘丝状形态类型，该形态类型在反应器中意外富集。从形态学上看，这种丝状形态与广泛存在于活性污泥废水处理系统中膨胀问题相关的艾克布姆形态类型0041 - 0675相符。对生物反应器污泥进行透射电子显微镜观察表明，鞘丝状形态类型具有典型的革兰氏阳性细胞包膜超微结构。因此，TM7是已知的第三个具有革兰氏阳性代表菌的细菌谱系。对两个全规模污水处理厂污泥（包括用于接种实验室规模反应器的污泥）进行TM7特异性FISH分析，结果表明存在多种形态类型，包括鞘丝形态。从这两个全规模污泥中制备的TM7特异性PCR克隆文库产生了23个新的TM7序列。基于这些数据以及公开可用序列，可以定义三个亚类。环境序列数据和TM7特异性FISH分析表明，TM7类群的成员存在于各种陆地、水生和临床生境中。几乎所有TM7序列中都存在一种细菌16S rRNA的高度非典型碱基替换（大肠杆菌位置912；C突变为U），这表明TM7细菌可能像古细菌一样，在核糖体水平上对链霉素具有抗性。
