Summary auto-generated
This study describes the isolation and characterization of Clostridium methoxybenzovorans sp. nov., a novel anaerobic bacterium isolated from an olive mill wastewater treatment digester in Tunisia. The bacterium is a strictly anaerobic, spore-forming, Gram-positive rod that uniquely degrades a wide range of methoxylated aromatic compounds through o-demethylation reactions. Strain SR3T utilizes numerous substrates including carbohydrates (glucose, fructose, lactose), organic compounds (lactate, betaine), and alcohols, with yeast extract required for growth. Fermentation produces acetate and butyrate from aromatic compounds, plus formate, hydrogen, and ethanol from carbohydrates. The organism is a mesophile with optimal growth at 37°C and pH 7.4, showing a DNA G+C content of 44 mol%. Phylogenetically, 16S rRNA analysis reveals closest relationships to Clostridium xylanolyticum, C. aerotolerans, C. sphenoides, and C. celerecrescens with 98% sequence similarity. Unlike some related homoacetogens, this organism performs o-demethylation without subsequent aromatic ring cleavage, producing hydroxylated derivatives as intermediates.
Key findings
- Clostridium methoxybenzovorans is a novel anaerobic homoacetogen capable of o-demethylating a diverse range of methoxylated aromatic compounds found in olive mill wastewater
- The organism performs o-demethylation in a two-step process forming 5-hydroxyvanillate as an intermediate that is degraded to gallate, without cleaving the aromatic ring
- The bacterium has a 44 mol% G+C content and is phylogenetically most closely related to non-methoxylated aromatic-degrading Clostridium species within cluster XIVa
- Strain SR3T is a mesophilic spore-former requiring yeast extract for growth and producing acetate, butyrate, formate, and ethanol as fermentation end products depending on substrate
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Abstract
T Mechichi, M Labat, BKC Patel, THS Woo, P Thomas and JL Garcia
Laboratoire ORSTOM de Microbiologie des Anaerobies, Universite de Provence, CESB-ESIL case 925, 163 Avenue de Luminy, 13288 Marseille Cedex 9, France
A strictly anaerobic, spore-forming bacterium (3.0--5.0 x 0.4--0.8 microm), designated strain SR3(T) ((T)=type strain), which stained Gram-positive and possessed a Gram-positive type cell wall was isolated from a methanogenic pilot-scale digester fed with olive mill wastewater (Sfax, Tunisia). It utilized a number of carbohydrates (glucose, fructose, sorbose, galactose, myo-inositol, sucrose, lactose, cellobiose), organic compounds (lactate, betaine, sarcosine, dimethylglycine, methanethiol, dimethylsulfide), alcohol (methanol) and all methoxylated aromatic compounds only in the presence of yeast extract (0.1%). The end products from carbohydrate fermentation were H(2), CO(2), formate, acetate and ethanol, that from lactate was methanol, those from methoxylated aromatics were acetate and butyrate, and that from betaine, sarcosine, dimethylglycine, methanethiol and dimethylsulfide was only acetate. Strain SR3(T) was non-motile, had a G+C content of 44 mol% and grew optimally at 37 degrees C and pH 7.4 on a glucose-containing medium. Phylogenetically, the closest relatives of strain SR3(T) were the non-methoxylated aromatic-degrading Clostridium xylanolyticum, Clostridium aerotolerans, Clostridium sphenoides and Clostridium celerecrescens (mean similarity of 98%). On the basis of the phenotypic, genotypic and phylogenetic characteristics of the isolate, it is proposed to designate strain SR3(T) as Clostridium methoxybenzovorans sp. nov. The type strain is SR3(T) (=DSM 12182(T)).