Vol. 46, No. 2
Isolation and Characterization of Sporobacter ternitidis gen. nov., sp. nov., from the Digestive Tract of the Wood-Feeding Termite Nasutitemes lujae
I. GRECH-MORA,'32 M.-L. FARDEAU,' B. K. C. PATEL,'.3 B. OLLIVIER,'*A. RIMBAULT,4 G. PRENSIER,s J.-L. GARCIA,' AND E. GARNIER-SILLAM2 Laboratoire de Microbiologie Institut FranGais de Recherche ScientiJique pour le Dtveloppement en Cooptration (ORSTOM), Universitt de Provence CESB-ESIL, 13288 Marseille Cedex 9,' Laboratoire de Biologie des Sols et des Sidiments Continentam, Universiti Paris Val de Mame, 94010 Criteil Cedex, Laboratoire de Microbiologie,Universiti Rent Descartes, Faculti de Pharmacie, 75270 Paris Cedex 06,4 and Laboratoire de Microbiologie, Universitt Blaise Pascal, 63177 Aubikre Cedex,' France, and Faculty of Science and TechnoLogy, GriBth Universip, Brisbane, Queensland 411I , Australia3
A new chemoorganotrophic bacterium, strain SYRT (T = type strain), was isolated from the digestive tract of the wood-feeding termite Nasutitermeslujae. This organism was a slightly curved spore-forming rod-shaped bacterium. It had a gram-positive-typecell wall and was obligately anaerobic. It grew exclusively on a limited range of methylated aromatic compounds including 3,4,5-trimethoxycinnamate (TMC), sinapate (3,Sdimethoxy-4-hydroxycinnamate),3,4-dimethoxycinnamate,3,4,5-trimethoxybenzoate, ferulate, syringate(3,5-dimethoxy-4-hydroxybenzoate),and vanillate (4-hydroxy-3-methoxybenzoate)but not on carbohydrates, alcohols, or fatty acids. The isolate required yeast extract for growth. Strain SYRT grew optimally between 32 and 35°C and at pH values between 6.7 and 7.2, with NaCl concentrations from 0 to 5 g liter-', on TMC with a doubling time of about 25 h. During growth on TMC in the presence of sulfide or cysteine, dimethyl sulfideand acetate were produced, whereas methanethiol was an intermediary product of metabolism. The ring of the methoxylated aromatic compound was cleaved. The DNA base composition was 57 mol%guanine plus cytosine. Comparative 16s rRNA sequence analysis indicated that strain SYRT was distantly related to Eubacterium desmolans and Eubacterium plautii. On the basis of its distinct phylogenetic positionand physiological properties, strain SYRT has been designated a new species of a new genus, Sporobacter termitidis gen. nov., sp. nov. (= DSM 1006ST).
Termites play a major role in the tropics and the subtropics, owing to their ability to decompose plant litter. On the basis of their diet, they have been classified as wood feeders, soil feeders, and fungus growers (20,31). The digestive tract oftermites is colonized by a complex microbial consortium which produces acetate and other volatile fatty acids from the polysaccharide components and plant lignocellulose complexes. The volatile fatty acids (mainly acetate) are absorbed by the termites for conversion to energy (8, 38). Currently there is limited knowledge of the role played by the microbial consortium in the degradation of aromaticconstituents of lignocellulose, including lignin (11-13, 15, 16, 29). However, several studies have indicated that oxic and anoxic conditions exist (3, 4, 6, 40). One approach useful for assessing the potential for lignin degradation is to study the degradation of lignin monomers (and related aromatic compounds) by the populations of anaerobic or aerobic bacteria present in the termite digestivetract. Brune et al. (12) have given further evidence that the aromatic compounds tested, including benzoic acid, phenolic compounds, and ferulic acid, the only monosubstituted methoxyl aromatic compound tested, were completely mineralized under oxic conditions. Furthermore, previous studies have shown that anaerobic demethylation of aromatic compounds occurs but that the aromatic ring (nucleus)...