Ahmad A, Barry J P, Nelson D C
Section of Microbiology, University of California, Davis, California 95616, USA.
Appl Environ Microbiol. 1999 Jan;65(1):270-7. doi: 10.1128/AEM.65.1.270-277.1999.
Environmentally dominant members of the genus Beggiatoa and Thioploca spp. are united by unique morphological and physiological adaptations (S. C. McHatton, J. P. Barry, H. W. Jannasch, and D. C. Nelson, Appl. Environ. Microbiol. 62:954-958, 1996). These adaptations include the presence of very wide filaments (width, 12 to 160 microm), the presence of a central vacuole comprising roughly 80% of the cellular biovolume, and the capacity to internally concentrate nitrate at levels ranging from 150 to 500 mM. Until recently, the genera Beggiatoa and Thioploca were recognized and differentiated on the basis of morphology alone; they were distinguished by the fact that numerous Thioploca filaments are contained within a common polysaccharide sheath, while Beggiatoa filaments occur singly. Vacuolate Beggiatoa or Thioploca spp. can dominate a variety of marine sediments, seeps, and vents, and it has been proposed (H. Fossing, V. A. Gallardo, B. B. Jorgensen, M. Huttel, L. P. Nielsen, H. Schulz, D. E. Canfield, S. Forster, R. N. Glud, J. K. Gundersen, J. Kuver, N. B. Ramsing, A. Teske, B. Thamdrup, and O. Ulloa, Nature [London] 374:713-715, 1995) that members of the genus Thioploca are responsible for a significant portion of total marine denitrification. In order to investigate the phylogeny of an environmentally dominant Beggiatoa sp., we analyzed complete 16S rRNA gene sequence data obtained from a natural population found in Monterey Canyon cold seeps. Restriction fragment length polymorphism analysis of a clone library revealed a dominant clone, which gave rise to a putative Monterey Beggiatoa 16S rRNA sequence. Fluorescent in situ hybridization with a sequence-specific probe confirmed that this sequence originated from wide Beggiatoa filaments (width, 65 to 85 microm). A phylogenetic tree based on evolutionary distances indicated that the Monterey Beggiatoa sp. falls in the gamma subdivision of the class Proteobacteria and is most closely related to the genus Thioploca. This vacuolate Beggiatoa-Thioploca cluster and a more distantly related freshwater Beggiatoa species cluster form a distinct phylogenetic group.
贝日阿托氏菌属（Beggiatoa）和辫硫菌属（Thioploca spp.）在环境中占主导地位的成员具有独特的形态和生理适应性（S. C. 麦克哈顿、J. P. 巴里、H. W. 扬纳施和D. C. 纳尔逊，《应用与环境微生物学》62:954 - 958，1996年）。这些适应性包括存在非常宽的丝状体（宽度为12至160微米）、存在一个约占细胞生物体积80%的中央液泡，以及在细胞内将硝酸盐浓缩至150至500 mM水平的能力。直到最近，贝日阿托氏菌属和辫硫菌属仅基于形态学来识别和区分；它们的区别在于，众多辫硫菌的丝状体包含在一个共同的多糖鞘内，而贝日阿托氏菌的丝状体单独存在。含液泡的贝日阿托氏菌或辫硫菌属物种可在各种海洋沉积物、渗流区和喷口区占主导地位，并且有人提出（H. 福辛、V. A. 加拉尔多、B. B. 乔根森、M. 胡特尔、L. P. 尼尔森、H. 舒尔茨、D. E. 坎菲尔德、S. 福斯特、R. N. 格鲁德、J. K. 冈德森、J. 库弗、N. B. 拉姆辛、A. 特斯克、B. 桑德鲁普和O. 乌略亚，《自然》[伦敦]374:713 - 715，1995年），辫硫菌属的成员对海洋总反硝化作用的很大一部分负责。为了研究一种在环境中占主导地位的贝日阿托氏菌的系统发育，我们分析了从蒙特雷峡谷冷渗流区的一个自然种群中获得的完整16S rRNA基因序列数据。对一个克隆文库的限制性片段长度多态性分析揭示了一个优势克隆，它产生了一个假定的蒙特雷贝日阿托氏菌16S rRNA序列。用序列特异性探针进行荧光原位杂交证实该序列源自宽的贝日阿托氏菌丝状体（宽度为65至85微米）。基于进化距离构建的系统发育树表明，蒙特雷贝日阿托氏菌属于变形菌纲γ亚纲，与辫硫菌属关系最为密切。这个含液泡的贝日阿托氏菌 - 辫硫菌簇和一个亲缘关系较远的淡水贝日阿托氏菌物种簇形成了一个独特的系统发育类群。
