CHARACTERIZATION OF A MANGANESE-REDUCING, TOLUENE-DEGRADING ENRICHMENT CULTURE

A bacterial culture (LET-13) was enriched, which uses toluene as sole carbon and energy source, and manganese oxide as terminal electron acc eptor. The culture is able to degrade a variety of substituted monoaro matic compounds like p-hydroxy-benzylalcohol, p-hydroxy-benzaldehyde, p-hydroxy-benzoate, phenol and the three isomers of cresol. Benzene, e thylbenzene, all xylenes and naphthalene were not degraded under the e xperimental conditions used. Based on the results of growth experiment s and the detection of intermediates, it is concluded that toluene is degraded via a methyl hydroxylation. A possible side reaction can lead to the formation of cresol. The organisms in the culture look similar ; motile rods, which are Gramnegative, oxidase-negative and catalase-n egative. The culture was partly identified by phylogenetic analysis of cloned rDNA sequences. The phylogenetic analysis showed that at least two major groups of bacteria are present. One group of bacteria shows 70-80% similarity (based on 16S rRNA gene sequence data) with the Bac teroides-Cytophaga group, and one group consists of members of the bet a-subclass of the Proteobacteria.