Vigliotta Giovanni, Nutricati Eliana, Carata Elisabetta, Tredici Salvatore M, De Stefano Mario, Pontieri Paola, Massardo Domenica Rita, Prati Maria Vittoria, De Bellis Luigi, Alifano Pietro
Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università degli Studi di Lecce, Via Monteroni, 73100 Lecce, Italy.
Appl Environ Microbiol. 2007 Jun;73(11):3556-65. doi: 10.1128/AEM.02678-06. Epub 2007 Apr 6.
Crenothrix polyspora Cohn 1870 and Clonothrix fusca Roze 1896 are two filamentous, sheathed microorganisms exhibiting complex morphological differentiation, whose phylogeny and physiology have been obscure for a long time due to the inability to cultivate them. Very recently, DNA sequencing data from uncultured C. polyspora-enriched material have suggested that Crenothrix is a methane-oxidizing gamma-proteobacterium (39). In contrast, the possible ecological function of C. fusca, originally considered a developmental stage of C. polyspora, is unknown. In this study, temporal succession of two filamentous, sheathed microorganisms resembling Cohn's Crenothrix and Roze's Clonothrix was observed by analyzing the microbial community of an artesian well by optical microscopy. Combined culture-based and culture-independent approaches enabled us to assign C. fusca to a novel subgroup of methane-oxidizing gamma-proteobacteria distinct from that of C. polyspora. This assignment was supported by (i) methane uptake and assimilation experiments, (ii) ultrastructural data showing the presence in C. fusca cytoplasm of an elaborate membrane system resembling that of methanotrophic gamma-proteobacteria, and (iii) sequencing data demonstrating the presence in its genome of a methanol dehydrogenase alpha subunit-encoding gene (mxaF) and a conventional particulate methane mono-oxygenase alpha subunit-encoding gene (pmoA) that is different from the unusual pmoA (u-pmoA) of C. polyspora.
多孢泉发菌（Crenothrix polyspora Cohn，1870年）和暗褐鞘丝菌（Clonothrix fusca Roze，1896年）是两种丝状、具鞘的微生物，表现出复杂的形态分化，由于无法对其进行培养，它们的系统发育和生理学长期以来一直不清楚。最近，来自未培养的富含多孢泉发菌材料的DNA测序数据表明，泉发菌是一种甲烷氧化γ-变形菌（39）。相比之下，最初被认为是多孢泉发菌一个发育阶段的暗褐鞘丝菌的可能生态功能尚不清楚。在本研究中，通过光学显微镜分析自流井的微生物群落，观察到了两种类似于科恩氏泉发菌和罗兹氏鞘丝菌的丝状、具鞘微生物的时间演替。基于培养和不依赖培养的方法相结合，使我们能够将暗褐鞘丝菌归为甲烷氧化γ-变形菌的一个新亚群，与多孢泉发菌不同。这一归类得到了以下几方面的支持：（i）甲烷吸收和同化实验；（ii）超微结构数据显示暗褐鞘丝菌细胞质中存在一个类似于甲烷营养γ-变形菌的精细膜系统；（iii）测序数据表明其基因组中存在一个编码甲醇脱氢酶α亚基的基因（mxaF）和一个传统的颗粒甲烷单加氧酶α亚基编码基因（pmoA），该基因与多孢泉发菌不同寻常的pmoA（u-pmoA）不同。
