A novel interdomain consortium from a Costa Rican oil well composed of Methanobacterium cahuitense sp. nov. and Desulfomicrobium aggregans sp. nov.

A novel interdomain consortium composed of a methanogenic Archaeon and a sulfate-reducing bacterium was isolated from a microbial biofilm in an oil well in Cahuita National Park, Costa Rica. Both organisms can be grown in pure culture or as stable co-culture. The methanogenic cells were non-motile rods producing CH exclusively from H/CO. Cells of the sulfate-reducing partner were motile rods forming cell aggregates. They utilized hydrogen, lactate, formate, and pyruvate as electron donors. Electron acceptors were sulfate, thiosulfate, and sulfite. 16S rRNA sequencing revealed 99% gene sequence similarity of strain CaP3V-M-L2A to Methanobacterium subterraneum and 98.5% of strain CaP3V-S-L1A to Desulfomicrobium baculatum. Both strains grew from 20 to 42 °C, pH 5.0-7.5, and 0-4% NaCl. Based on our data, type strains CaP3V-M-L2A (= DSM 113354 = JCM 39174) and CaP3V-S-L1A (= DSM 113299 = JCM 39179) represent novel species which we name Methanobacterium cahuitense sp. nov. and Desulfomicrobium aggregans sp. nov.