Clostridium tunisiense sp. nov., a new proteolytic, sulfur-reducing bacterium isolated from an olive mill wastewater contaminated by phosphogypse

Abstract

A new sporulated fermentative bacterium designated strain E1 T (T=type strain), was isolated from an anaerobic mud of an olive mill wastewater basin contaminated by phosphogypse produced by a Tunisian factory. Strain E1 T was a motile Gram-positive slightly curved rod with spherical terminal spore swelling the cell. It grew between 18°C and 43°C with an optimum at 37°C and pH 7.8 (range 5.5–8.7), without NaCl (range 0–3%). Strain E1 T was a chemoorganotrophic anaerobic bacterium fermenting only proteins and amino acids. Yeast extract was required for growth. Elemental sulfur was used as terminal electron acceptor. The G+C content of the DNA was 32.6 mol%. The closest phylogenetical relatives of strain E1 T were Clostridium thiosulfatireducens and C. subterminale (97.3% similarity for partial rRNA gene sequences). DNA–DNA hybridization values between strain E1 T and both species were 17% and 20.8%, respectively. On the basis of differences in genotypic and phenotypic characteristics, strain E1 T (DSM 15206 T, CIP 107666 T) is proposed as the type strain of a new species, C. tunisiense sp. nov. GenBank accession number for the 16S rRNA gene sequence of strain E1 T is AY187622.