Soehngenia saccharolytica gen.nov., sp.nov. and Clostridium amygdalinum sp.nov., two novel anaerobic benzaldehyde-converting bacteria

Two anaerobic, benzaldehyde-converting bacteria were isolated from an anaerobic upflow anaerobic sludge bed (UASB)-reactor treating potato starch waste water. Strain BOR-Y-T converted benzaldehyde to benzoate and benzylalcohol in approximately equimolar concentrations. Benzaldehyde conversion did not support growth. Strain BOR-Y-T was Gram-positive and rod-shaped, and its cells were slightly thickened in the middle. The strain was a mesophilic spore-former that grew between 15 and 40 degreesC, with optimum growth at 30-37 degreesC. The optimum pH for growth was pH 7(.)0. Strain BOR-Y-T grew on a wide range of carbohydrates and some other carbon sources including yeast extract, cysteine and serine. The G + C content of its DNA was 42 mol%. According to physiological characteristics and 16S rRNA gene sequence analysis, confirmed by DNA-DNA hybridization with its phylogenetic neighbours, strain BOR-Y-T belongs to a novel genus of cluster XII of the clostridia, namely Soehngenia; the name Soehngenia saccharolytica is proposed for the type species (type strain BOR-Y-T = DSM 12858(T) ATCC BAA-502(T)). Strain BR-10(T) reduced benzaldehyde to benzylalcohol. This conversion was coupled to growth. In a medium containing yeast extract, the presence of benzaldehyde resulted in the accumulation of more than twofold more cells. Strain BR-10(T) was a Gram-positive organism that was characterized by oval- or rod-shaped cells with oval ends, which occurred singly, in pairs or sometimes in chains. The strain was moderately thermophilic and grew between 20 and 60 degreesC, with optimum growth at 45 degreesC. The optimum pH for growth was between pH 7(.)0 and 7(.)5. Strain BR-10(T) grew on a wide range of carbon sources including carbohydrates, yeast extract, casein and some amino acids. The G + C content of its DNA was 32 mol%. As determined by 16S rRNA gene sequence analysis, strain BR-10(T) represents a novel species of cluster XIVa of the clostridia; the name Clostridium amygdalinum is proposed for this novel species (type strain BR-10(T) = DSM 12857(T) = ATCC BAA-501(T))

Nitrification expanded: discovery, physiology and genomics of a nitrite-oxidizing bacterium from the phylum <i>Chloroflexi</i>

Nitrite-oxidizing bacteria (NOB) catalyze the second step of nitrification, a major process of the biogeochemical nitrogen cycle, but the recognized diversity of this guild is surprisingly low and only two bacterial phyla contain known NOB. Here, we report on the discovery of a chemolithoautotrophic nitrite oxidizer that belongs to the widespread phylum Chloroflexi not previously known to contain any nitrifying organism. This organism, named Nitrolancetus hollandicus, was isolated from a nitrifying reactor. Its tolerance to a broad temperature range (25-63 degrees C) and low affinity for nitrite (K-s = 1 mM), a complex layered cell envelope that stains Gram positive, and uncommon membrane lipids composed of 1,2-diols distinguish N. hollandicus from all other known nitrite oxidizers. N. hollandicus grows on nitrite and CO2, and is able to use formate as a source of energy and carbon. Genome sequencing and analysis of N. hollandicus revealed the presence of all genes required for CO2 fixation by the Calvin cycle and a nitrite oxidoreductase (NXR) similar to the NXR forms of the proteobacterial nitrite oxidizers, Nitrobacter and Nitrococcus. Comparative genomic analysis of the nxr loci unexpectedly indicated functionally important lateral gene transfer events between Nitrolancetus and other NOB carrying a cytoplasmic NXR, suggesting that horizontal transfer of the NXR module was a major driver for the spread of the capability to gain energy from nitrite oxidation during bacterial evolution. The surprising discovery of N. hollandicus significantly extends the known diversity of nitrifying organisms and likely will have implications for future research on nitrification in natural and engineered ecosystems. The ISME Journal (2012) 6, 2245-2256; doi:10.1038/ismej.2012. 70; published online 5 July 201