Cryptanaerobacter phenolicus gen. nov., sp. nov., an anaerobe that transforms phenol into benzoate via 4-hydroxybenzoate

Abstract

An anaerobic bacterium that transforms phenol and 4-hydroxybenzoate (4-OHB) into benzoate, strain LR7.2T, was isolated from a culture originating from a mixture of swamp water, sewage sludge, swine waste and soil. Cells of strain LR7.2T are Gram-positive short rods (1×2 μm) that are electron-dense when observed by electron microscopy. The optimum pH and temperature for growth and transformation activity of 4-OHB are 7·5–8·0 and 30–37 °C, respectively. The bacterium does not use sulphate, thiosulphate, nitrate, nitrite, FeCl3, fumarate or arsenate as an electron acceptor. It does not normally use sulphite, although stimulation of growth and 4-OHB transformation activity at a low concentration (up to 2 mM) has been reported previously under different culture conditions. The presence of 4-OHB or phenol is essential for growth; transformation of 4-OHB or phenol into benzoate is used to produce energy for growth. Using [6D]-phenol, 4-OHB was shown to be an intermediate in the transformation of phenol into benzoate. No spore was observed. The bacterium has a DNA G+C content of 51 mol% and its major membrane fatty acid is anteiso-C15 : 0. The 16S rRNA gene sequence of strain LR7.2T shows only 90 % similarity to its closest relative (Pelotomaculum thermopropionicum). From these results, a new taxon is proposed: Cryptanaerobacter phenolicus gen. nov., sp. nov. The type strain is LR7.2T (=ATCC BAA-820T=DSM 15808T).