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A novel species, Methylocella tundrae, is proposed for three methanotrophic strains (T4 T , TCh1 and TY1) isolated from acidic Sphagnum tundra peatlands. These strains are aerobic, Gram-negative, non-motile, dinitrogen-fixing rods that possess a soluble methane monooxygenase and utilize the serine pathway for carbon assimilation. Strains T4

This ad hoc committee was formed following the workshop on reconciliation of approaches to bacterial systematics (8) because it was realized that the "purple bacteria and their relatives," now termed proteobacteria at the class level (6), formed a major and very diverse assemblage consisting of a related set of lineages ("alpha," "beta," "gamma," and "delta" groups at the level of subclass [7, 91 or "superfamilies" [2]) recognized on the basis of homologies within the sequences in their rRNA. This complex assemblage of bacteria, important in all aspects of bacteriology, was evidently based on a stem that included phototrophy but had evolved to include a great variety of other physiological capabilities. The diversity of this class presents taxonomic problems at a number of levels, particularly in approaching ranks above the level of genus. Aside from the need to understand the nature of bacterial evolution and interpret the traces left in macromolecular semantides (9, lo), there were more obvious and practical problems presented by established genera founded on phenotypic attributes which show genetic heterogeneity and by phylogenetic groupings encompassing an extreme variety of phenotypes (6).There was agreement with the opinion of the earlier ad hoc committee, that the combination of the best of phenotypic studies and the conclusions developed from phylogenetic analyses can develop effective grouping, often expressing similar conclusions about natural hierarchic structure. There was agreement that the sequences represented in rRNAs provide the only resource so far recognized for both discerning and testing phylogenetic associations that has the appropriate qualities of universality, genetic stability, and conservation of structure. It was evident that bacteriologists and taxonomists should be encouraged to recognize that modern natural classification requires as complete a data set as possible, integrating phenotypic and genotypic information. No single method in either area is sufficient for all taxa. For these reasons, it was concluded that the acquisition of high-quality data and a mechanism for access to it are essential for future development of taxonomic conclusions.Application of phylogenetic data. It was previously established that DNA-DNA hybridization is the standard arbiter

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Schlesneria paludicola gen. nov., sp. nov., the first acidophilic member of the order Planctomycetales, from Sphagnum-dominated boreal wetlands Three strains of budding, ellipsoid-shaped and rosette-forming bacteria were isolated from acidic Sphagnum-dominated boreal wetlands of northern Russia and were designated strains MPL7 T , MOB77 and SB2. The presence of crateriform pits and numerous fibrillar appendages on the cell surface and an unusual spur-like projection on one pole of the cell indicated a planctomycete morphotype. These isolates are moderately acidophilic, mesophilic organisms capable of growth at pH values between 4.2 and 7.5 (with an optimum at pH 5.0-6.2) and at temperatures between 4 and 32 6C (optimum 15-26 6C). The major fatty acids are C 16 : 0 and C 16 : 1 v7c; the major quinone is MK-6. The G+C content of the DNA is 54.4-56.5 mol%. Strains MPL7 T , MOB77 and SB2 possess nearly identical 16S rRNA gene sequences and belong to the planctomycete lineage defined by the genus Planctomyces, being most closely related to Planctomyces limnophilus DSM 3776 T (86.9-87.1 % sequence similarity). However, strain MPL7 T showed only 28 % DNA-DNA hybridization with P. limnophilus DSM 3776T . Compared with currently described members of the genus Planctomyces, the isolates from northern wetlands do not form long and distinctive stalks, have greater tolerance of acidic conditions and low temperatures, are more sensitive to NaCl, lack pigmentation and degrade a wider range of biopolymers. The data therefore suggest that strains MPL7 T , MOB77 and SB2 represent a novel genus and species, for which the name Schlesneria paludicola gen. nov., sp. nov., is proposed. Strain MPL7T (5ATCC BAA-1393 T 5VKM B-2452 T ) is the type strain of Schlesneria paludicola.The order Planctomycetales comprises a remarkable group of budding bacteria that possess highly distinctive cell morphology, peptidoglycan-less cell walls and a unique cell organization (König et al., 1984;Schlesner & Stackebrandt, 1986;Staley et al., 1992;Fuerst, 1995Fuerst, , 2004Fuerst, , 2005Ward et al., 2006). Originally described as freshwater organisms, members of this order were later shown to be ubiquitous in a wide range of aquatic and terrestrial environments with diverse conditions. Despite the reported widespread distribution, the known ecophysiological types of planctomycetes are quite limited. With the only exception of moderately thermophilic Isosphaera pallida (Giovannoni et al., 1987), all taxonomically described planctomycetes are both mesophilic and neutrophilic.Until recently, there has been only one report on the isolation of a planctomycete-like strain from an acidic environment, i.e. peat bog water (pH 4.2) of the Kaltenhofer Moor near Kiel, Germany (Schlesner, 1994). This strain has not been described taxonomically, and no further information except a brief morphologicalAbbreviations: FAME, fatty acid methyl ester; PLFA, phospholipid fatty acid.The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain MPL7 T is AM162...