Co-culture of defined bacteria to degrade seven sulfonated aromatic compounds : efficiency, rates and phenotypic variations

Abstract

A co-culture, consisting of five defined bacteria [e.g., T. Thurnheer, T. Köhler, A. M. Cook, and T. Leisinger: J Gen Microbiol 132:1215 1220], was able to degrade at least seven substituted benzenesulfonic acids in continuous culture. HPLC, total organic carbon analyses and colourimetric analyses showed that the sulfonated compounds could be completely degraded to biomass, SO 4 2-, NH 4 + and CO2. The maximum observed degradation rate was 138 mg of C/h·1. The five organisms were Alcaligenes sp. strain 0 1 (substrates benzenesulfonic acid, 4-methylbenzenesulfonic acid and 2-aminobenzenesulfonic acid), two Pseudomonas spp., strains T-2 (substrates 4-methylbenzenesulfonic acid and 4-sulfobenzoic acid) and PSB-4 (substrate 4-sulfobenzoic acid) and two unidentified rods, strains M-1 (substrates benzenesulfonic acid, 4-methylbenzenesulfonic acid and 3-aminobenzenesulfonic acid) and S-1 (substrates 4-aminobenzenesulfonic acid and 4-hydroxybenzenesulfonic acid). The system was operated for over 18 months with five sulfonates, and no competition was detected amongst the four organisms present, because all organisms were still present (100% of the population after 7 months, 55% after 18 months). Many bacteria isolated from the continuous culture after 18 months showed substrate ranges different from those of the original strains. The most common occurrence (33% of the population) was the appearance of organisms which could degrade 2-aminobenzenesulfonic acid and 4-sulfobenzoic acid. Several cases of the loss of a character were seen but only rarely (1%) was a net gain of characters observed. After 30 months, only two (of five) parents were present (35% of the population) and some isolates could utilize all seven substrates on solid media.