Diversity of Freshwater Thioploca Species and Their Specific Association with Filamentous Bacteria of the Phylum Chloroflexi

Abstract

Phylogenetic diversity among filamentous sulfur-oxidizing bacteria of the genus Thioploca inhabiting freshwater/brackish environments was analyzed in detail.The 16S rRNA gene sequence of Thioploca found in a freshwater lake in Japan, Lake Okotanpe, was identical to that of Thioploca from Lake Ogawara, a brackish lake. The samples of two lakes could be differentiated by the sequences of their 23S rRNA genes and 16S-23S rRNA internal transcribed spacer (ITS) regions. The 23S rRNA-based phylogenetic relationships between Thioploca samples from four lakes (Lake Okotanpe, Lake Ogawara, Lake Biwa, and Lake Constance) were similar to those based on the 16S rRNA gene sequences. In addition, multiple types of the ITS sequences were obtained from Thioploca inhabiting Lake Okotanpe and Lake Constance. Variations within respective Thioploca populations were also observed in the analysis of the soxB gene, involved in sulfur oxidation. As major members of the sheath-associated microbial community, bacteria of the phylum Chloroflexi were 3 consistently detected in the samples from different lakes. Fluorescence in situ hybridization (FISH) revealed that they were filamentous and abundantly distributed within the sheaths of Thioploca.4

Filamentous sulfur-oxidizing bacteria of the genus Thioploca from Lake Tonle Sap in Cambodia

“…The phylogenetic diversity within Thioploca of Lake Tonle Sap was consistently shown in the analyses of 16S rRNA, 23S rRNA, and the ITS region. In other habitats, only a single 16S rRNA gene sequence of Thioploca has been reported from each lake (Kojima et al 2003, 2006, Zemskaya et al 2009, Nemoto et al 2011, although the coexistence of different sequences was reported in a brackish fjord (Høgslund et al 2010, Salman et al 2011. In the present study, DNA was extracted from a clump of tangled filaments obtained by sieving bulk sediment.…”

“…Subsequently, populations were reported from Lake Erie and Lake Ontario in North America (Maier & Murray 1965, Dermott & Legner 2002, Lake Baikal in Siberia (Zemskaya et al 2001), and Lake Biwa, Lake Ogawara, and Lake Okotanpe in Japan (Nishino et al 1998, Kojima et al 2006, Nemoto et al 2011. These lakes are located in areas of mid-range to high latitudes in the northern hemisphere.…”

“…Several multicellular filaments (trichomes) form bundles surrounded by a common sheath, and each trichome can glide independently within the common sheath. Early descriptions of Thioploca used the diameter of the trichome as a characteristic to discriminate species (Lauterborn 1907, Wislouch 1912, Maier 1984; most of the recent studies were performed on samples with trichome diameters of ~4 µm (Zemskaya et al 2001, Kojima et al 2003, 2006, Høgslund et al 2010, Nemoto et al 2011. Until recently, this genus also included marine species with much thicker trichomes, but a new independent candidate genus, 'Candidatus Marithioploca', has now been proposed to encompass these species (Salman et al 2011).…”

“…According 66: 295-300, 2012 to the classification recently proposed (Salman et al 2011), the present study is the first report of the genus Thioploca from a tropical area. To date, members of the genus Thioploca have been reported only from temperate and subarctic areas (Lauterborn 1907, Maier & Murray 1965, Zemskaya et al 2001, Dermott & Legner 2002, Kojima et al 2003, 2006, Høgslund et al 2010, Nemoto et al 2011. Among these lakes and fjords, Lake Biwa is located at the lowest latitude.…”

Sulfurirhabdus autotrophica gen. nov., sp. nov., isolated from a freshwater lake

“…The type strain of Sulfuricella denitrificans was isolated from a cold anoxic hypolimnion of a freshwater lake, and was characterized as a psychrotolerant sulfur oxidizer (Watanabe et al, 2012). Based on nucleotide sequences, its close relatives have been found in freshwater lake sediments (Nelson et al, 2007;Song et al, 2012;Watanabe et al, 2013), Thioploca samples from two freshwater lakes (Nemoto et al, 2011), drinking water distribution systems (Li et al, 2010;Sun et al, 2014a, b), the sediment of a drinking water reservoir (Cheng et al, 2014), soil (Field et al, 2010), a bioreactor (Wang et al, 2015), subglacial sediment (Boyd et al, 2014), wetland sediment (Liu et al, 2014), a limestone aquifer (Herrmann et al, 2015), groundwater (Hong et al, 2013), black shale (Li et al, 2014), a horizontal subsurface flow system constructed in wetlands (Zhong et al, 2015) and the freshwater layer of a meromictic lake (Kubo et al, 2014). Members of the genus Sulfuricella are likely to contribute to sulfur cycling in a wide range of freshwater ecosystems, but only two cultured strains of the genus Sulfuricella have, so far, been described (Watanabe et al, 2015b).…”