Spring S, Lins U, Amann R, Schleifer K H, Ferreira L C, Esquivel D M, Farina M
Lehrstuhl für Mikrobiologie, Technische Universität München, D-80290 München, Germany,
Arch Microbiol. 1998 Feb;169(2):136-47. doi: 10.1007/s002030050553.
Natural enrichments of magnetic bacteria from the Itaipu lagoon near Rio de Janeiro were dominated by coccoid-to-ovoid morphotypes that produced unusually large magnetosomes. To determine the phylogenetic position of these unusual microorganisms, 16S rRNA genes were retrieved from bacteria magnetically separated from sediment of the Itaipu lagoon by in vitro amplification and cloning of PCR products into a plasmid vector. Partial sequencing of the obtained clones revealed two clusters of closely related sequences affiliated to a distinct lineage consisting exclusively of magnetic bacteria within the alpha-subclass of Proteobacteria. For a detailed phylogenetic analysis, several almost complete sequences of the 16S rRNA genes were determined. One representative clone of each cluster provided a PCR template for the in vitro transcription of group-specific polynucleotide probes complementary to a variable region of the 16S rRNA molecule. At least three different morphotypes of magnetic bacteria were reliably identified by post-embedding hybridization of ultra-thin sections. Electron microscopic analyses of hybridized cells enabled for the first time a detailed description of the morphological variety and ultrastructure of phylogenetically identified, uncultured magnetic bacteria. Two distinct coccoid bacteria were identified by the transcript probe complementary to the 16S rRNA sequence mabrj12, whereas the probe complementary to the sequence mabrj58 allowed the identification of an ovoid morphotype that displayed magnetosomes with the largest volumes observed to date.
来自里约热内卢附近伊泰普泻湖的磁性细菌自然富集物主要由球状到卵形的形态类型组成，这些形态类型产生异常大的磁小体。为了确定这些异常微生物的系统发育位置，通过体外扩增并将聚合酶链反应（PCR）产物克隆到质粒载体中，从伊泰普泻湖沉积物中磁性分离出的细菌中检索16S核糖体RNA（rRNA）基因。对获得的克隆进行部分测序，发现两个紧密相关序列的簇，它们隶属于一个独特的谱系，该谱系仅由变形菌门α亚类中的磁性细菌组成。为了进行详细的系统发育分析，测定了几个16S rRNA基因的几乎完整序列。每个簇的一个代表性克隆为体外转录与16S rRNA分子可变区互补的组特异性多核苷酸探针提供了PCR模板。通过超薄切片的包埋后杂交，可靠地鉴定出至少三种不同形态类型的磁性细菌。对杂交细胞的电子显微镜分析首次能够详细描述系统发育鉴定的未培养磁性细菌的形态多样性和超微结构。与16S rRNA序列mabrj12互补的转录探针鉴定出两种不同的球状细菌，而与序列mabrj58互补的探针则鉴定出一种卵形形态类型，该形态类型显示出迄今观察到的体积最大的磁小体。
