Berlanga Mercedes, Aas Jorn A, Paster Bruce J, Boumenna Tahani, Dewhirst Floyd E, Guerrero Ricardo
Department of Microbiology and Parasitology, University of Barcelona, Spain.
Int Microbiol. 2008 Dec;11(4):267-74. doi: 10.2436/20.1501.01.71.
Spirochetes are among the bacterial groups often observed in hydrogen-sulfide-rich layers of coastal microbial mats. However, relatively few spirochetes from these microbial mats have been described and characterized. We used 16S rDNA phylogenetic analysis to investigate the spirochetal diversity of microbial mats from two locations in the western Mediterranean (Ebro Delta, Spain, and Camargue, France). Samples from each location were monitored in the spring and winter over a period of 1 to 2 years. In the sequence analysis of 332 clones derived from samples of both locations, 42 novel phylotypes of not-yet-cultivated spirochetes belonging to the genus Spirochaeta were detected. None of the phylotypes were identified as known culturable species of Spirochaeta or previously identified phylotypes cloned from other hypersaline microbial mat such as Guerrero Negro, Mexico. Eight of the phylotypes were common to Ebro and Camargue mats, and two (IF058 and LL066) were present both in spring and winter. Some phylotypes appeared to show seasonal variation, i.e., they were found only in the spring, but not in the winter. Ebro and Camargue phylotypes, like phylotypes from Guerrero Negro, grouped according to the vertical gradient of oxygen and sulfide in the mat. Some phylotypes, such as LH073, IE028, LH042, or LG013 were harbored in low H2S or H2S-O2 interface zone. In contrast, major phylotypes were detected in deeper layers and they were likely strict anaerobes and high tolerant to H2S. The presence of spirochetes in differently located microbial mats suggests that they constitute very diverse and stable populations involved in a well-integrated metabolic symbiosis (i.e., permanent physiological cooperation) with other guild populations in the mats, where they maintain a coordinated functional and stable community.
螺旋体是在沿海微生物席富含硫化氢的层中经常观察到的细菌类群之一。然而，来自这些微生物席的螺旋体相对较少被描述和表征。我们使用16S rDNA系统发育分析来研究西地中海两个地点（西班牙埃布罗三角洲和法国卡马尔格）微生物席的螺旋体多样性。在1至2年的时间里，对每个地点的样本在春季和冬季进行了监测。在对来自两个地点样本的332个克隆进行的序列分析中，检测到42种属于螺旋体属的尚未培养的螺旋体新系统型。没有一个系统型被鉴定为螺旋体属已知的可培养物种，也不是先前从其他高盐度微生物席（如墨西哥的格雷罗内格罗）克隆的已鉴定系统型。其中8个系统型在埃布罗和卡马尔格的微生物席中是常见的，还有两个（IF058和LL066）在春季和冬季都存在。一些系统型似乎表现出季节性变化，即它们只在春季被发现，而在冬季没有。埃布罗和卡马尔格的系统型，与来自格雷罗内格罗的系统型一样，根据微生物席中氧气和硫化物的垂直梯度进行分组。一些系统型，如LH073、IE028、LH042或LG013，存在于低硫化氢或硫化氢-氧气界面区。相比之下，主要的系统型在更深的层中被检测到，它们可能是严格厌氧菌，并且对硫化氢具有高耐受性。不同位置的微生物席中螺旋体的存在表明，它们构成了非常多样和稳定的种群，与微生物席中的其他群落种群参与了良好整合的代谢共生（即永久的生理合作），在其中它们维持着协调的功能和稳定的群落。
