Defluviitoga tunisiensis gen. nov., sp. nov., a thermophilic bacterium isolated from a mesothermic and anaerobic whey digester

Abstract

Defluviitoga tunisiensis gen. nov., sp. nov., a thermophilic bacterium isolated from a mesothermic and anaerobic whey digester T , a thermophilic, anaerobic and slightly halophilic, rod-shaped bacterium with a sheath-like outer structure (toga), was isolated from a whey digester in Tunisia. The strain's nonmotile cells measured 3-30¾1 mm and appeared singly, in pairs or as long chains. The novel strain reduced thiosulfate and elemental sulfur, but not sulfate or sulfite, into sulfide. It grew at 37-65 6C (optimum 55 6C), at pH 6.5-7.9 (optimum pH 6.9) and with 0.2-3 % (w/v) NaCl (optimum 0.5 %). The G+C content of the strain's genomic DNA was 33.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SulfLac1T was most closely related to Petrotoga mobilis (91.4 % sequence similarity). Based on phenotypic, phylogenetic and chemotaxonomic evidence, strain SulfLac1 T represents a novel species of a new genus within the order Thermotogales, for which the name Defluviitoga tunisiensis gen. nov., sp. nov. is proposed. The type strain of the type species is SulfLac1The cultivated representatives of the order Thermotogales are thermophilic anaerobes that are known to thrive in geothermally heated environments (Huber & Hannig, 2006). Members of this order include, for example, species of the genera Thermotoga, Marinitoga, Thermosipho and Fervidobacterium that were isolated from hot locations on the seafloor (Huber et al., 1986(Huber et al., , 1989Urios et al., 2004) such as deep-sea hydrothermal chimneys (Antoine et al., 1997; Wery et al., 2001;Postec et al., 2005), from a hot inland oil well (Fardeau et al., 2009) or from a hot spring (Patel et al., 1985). The species belonging to the other genera in the order Thermotogales (i.e. Petrotoga, Geotoga, Kosmotoga, Thermococcoides and Oceanotoga) were all isolated from oilfield ecosystems (Davey et al., 1993;Miranda-Tello et al., 2004 DiPippo et al., 2009;Feng et al., 2010;Jayasinghearachchi & Lal, 2011). Curiously, some mesothermic ecosystems, such as anaerobic waste digesters and contaminated sediments, contain bacteria that have 16S rRNA gene sequences similar to those of thermophilic members of the order Thermotogales (van Houten et al., 2009;Briones et al., 2007; Chouari et al., 2005). Whether such bacteria, called 'mesotoga', are truly mesophilic remains a matter of debate, however, as none of them has yet been cultivated (Nesbø et al., 2006(Nesbø et al., , 2010. The order Thermotogales comprises anaerobic, chemo-organotrophic, non-sporulating, rod-shaped bacteria that are characterized by a sheath-like outer structure known as a 'toga' (Huber et al., 1986;Miranda-Tello et al., 2004.The present study represents a taxonomic characterization of a novel thermophilic bacterium that was isolated from a mesothermic digester used to process whey. The bacterium was found to show phenotypic and phylogenetic traits that led to its assignment to a novel species of a novel genus within the order Thermotogales.Samples were collected from the sludge of...

Development and characterization of stable anaerobic thermophilic methanogenic microbiomes fermenting switchgrass at decreasing residence times

“…To our knowledge, this study is the first to capture a dynamic shift in relative abundance of a Thermotogae. D. tunisiensis is a primary fermenter capable of growing on microcrystalline cellulose [100], but the genome sequence of the L3 strain only encoded a GH5 cellulase [101]. The D. tunisiensis strain identified in this study encoded a GH5 cellulase but did not encode a GH48 cellulase (Additional file 13: Table S7), which was previously found to be an absolute requirement for pure culture crystalline cellulose hydrolysis in the genus Caldicellulosiruptor [102].…”

Biphasic Study to Characterize Agricultural Biogas Plants by High-Throughput 16S rRNA Gene Amplicon Sequencing and Microscopic Analysis

“…Comparison of the four biogas communities analyzed in this study revealed that the genera Defluviitoga and Halocella were highly abundant in the thermophilic BGP4. Members of both genera were described to grow at high temperatures of up to 50°C for Halocella cellulolytica [45] and 70°C for Defluviitoga tunisiensis [46]. Additionally, these organisms use a variety of carbohydrates such as cellulose, cellobiose, xylan, and xylose for acetate, CO…”

Inhibitory Effects of Ferrihydrite on a Thermophilic Methanogenic Community

“…In the non-Fe control cultures, the relative abundances of the three other major bacterial T-RFs dominated in the bacterial T-RF assemblages at the end of the cultivation experiments. C. proteolyticus , A. mobile , and D. tunisiensis are obligately anaerobic, fermentative bacteria that utilize various carbohydrate and proteinaceous compounds for growth and also generate acetate and H 2 /CO 2 as major fermentative products, but have different substrate utilization spectra (4, 15, 17). In the control cultures, these three bacterial species may have contributed to the degradation of organic compounds in the yeast extract to produce acetate and H 2 /CO 2 , which could then be converted into CH 4 by the methanogenic archaea.…”