Pladdies Teresa, Babenzien Hans-Dietrich, Cypionka Heribert
Institut für Chemie und Biologie des Meeres, Universität Oldenburg, D-26111, Oldenburg, Germany.
Microb Ecol. 2004 Apr;47(3):218-23. doi: 10.1007/s00248-003-1070-3. Epub 2004 Apr 2.
Samples from 27 natural and artificial aquatic environments were analyzed for the presence of rosette-forming bacteria by a combined cultivation and molecular biological approach. Rosette-forming bacteria developed in 20 enrichment cultures with ammonia-free medium under air. Three morphotypes could be distinguished. The most abundant type I resembled Nevskia ramosa and formed hydrophobic, flat, and dichotomously branching rosettes. Type II rosettes were three-dimensional and were observed in 10 enrichments, often together with those of type I. These rosettes were hydrophilic indicating life in the hyponeuston underneath the air-water interface. Rosettes of a third type consisted of hydrophilic slime stalks that were excreted at the cell poles and were observed in only one sample. Using fluorescence in situ hybridization (FISH) with the Nevskia-specific probes NEV177 and NEV656, the presence of Nevskia ramosa was demonstrated in exactly those samples that showed type I rosettes. In a series of most-probable-number experiments, during a calm and sunny weather period 430,000 Nevskia-like bacteria per mL were found in surface samples, while during rainy weather and within the water body the numbers were lower by several orders of magnitude. Five pure cultures isolated from various enrichments were characterized in detail. The two isolates forming type I rosettes were identified as Nevskia ramosa by 16S rDNA analysis. However, comparison by genomic fingerprinting (ERIC-PCR) revealed differences between the two isolates and previously characterized strains. The 16S rDNA of two isolates forming type II rosettes showed 97.6% similarity to that of Pseudomonas fluorescens. The closest relative of the isolate forming type III rosettes was Sphingomonas parapaucimobilis (96.4% sequence similarity of the 16S rRNA sequence). All isolates grew homogeneously submersed if ammonia was added to the medium. Our results indicate that Nevskia ramosa is a widely distributed epineustonic bacterium, which can specifically be deleted by its flat and hydrophobic rosettes on ammonia-free media.
采用培养与分子生物学相结合的方法，对来自27个自然和人工水生环境的样本进行分析，以检测是否存在形成莲座状的细菌。在无氨培养基的20种富集培养物中，在空气条件下培养出了形成莲座状的细菌。可区分出三种形态类型。最常见的I型类似于分枝涅瓦河菌，形成疏水、扁平且二叉分枝的莲座状结构。II型莲座状结构是三维的，在10种富集培养物中观察到，通常与I型莲座状结构共存。这些莲座状结构是亲水的，表明其生活在空气 - 水界面下方的水表上层。第三种类型的莲座状结构由在细胞极处分泌的亲水黏液柄组成，仅在一个样本中观察到。使用针对分枝涅瓦河菌的特异性探针NEV177和NEV656进行荧光原位杂交（FISH），在恰好显示I型莲座状结构的样本中证实了分枝涅瓦河菌的存在。在一系列最大可能数实验中，在平静且阳光充足的天气期间，表层样本中每毫升发现430,000个类似分枝涅瓦河菌的细菌，而在雨天和水体内部，数量则低几个数量级。对从各种富集培养物中分离出的5个纯培养物进行了详细表征。通过16S rDNA分析，鉴定出形成I型莲座状结构的两个分离株为分枝涅瓦河菌。然而，通过基因组指纹图谱（ERIC-PCR）比较发现，这两个分离株与先前表征的菌株存在差异。形成II型莲座状结构的两个分离株的16S rDNA与荧光假单胞菌的16S rDNA相似度为97.6%。形成III型莲座状结构的分离株的最接近亲缘种是少动鞘氨醇单胞菌（16S rRNA序列的序列相似度为96.4%）。如果向培养基中添加氨，所有分离株在完全浸没的情况下均能均匀生长。我们的结果表明，分枝涅瓦河菌是一种广泛分布的水表上层细菌，在无氨培养基上，其扁平且疏水的莲座状结构可将其特异性去除。
