Change in the Predominant Bacteria in a Microbial Consortium Cultured on Media Containing Aromatic and Saturated Hydrocarbons as the Sole Carbon Source

Abstract

A No.22 consortium was isolated from contaminated soils at oilfields by repeated transfer on a mineral salts medium with the aromatic hydrocarbon fraction from crude petroleum. The consortium was able to degrade aromatic hydrocarbons at high rates. Fourteen major DNA bands were detected in the consortium by PCR-DGGE. Three strains were capable of forming colonies on agarose plates containing mineral salts and aromatic hydrocarbons, and identified as Pandoraea sp. Y1, Hyphomicrobium facile Y3, and Burkholderia multivorans Y4 by 16S rRNA gene sequencing. The consortia of three cultures; an aromatic subculture, a saturated culture transferred from the subculture, and an aromatic obtained culture from the transferred culture, were compared using PCR-DGGE, a clone library, and quantitative real-time PCR. Burkholderia species containing strain Y4 became the dominant species in the saturated culture whereas its abundance decreased in the aromatic culture. Pandoraea sp. Y1, which was of low abundance in the saturated culture, and an unisolated bacterium, Brachymonas sp. F, in contrast, increased in the aromatic culture. The aromatic hydrocarbons were degraded by Pandoraea sp. Y1 and B. multivorans Y4, whereas the saturates were only degraded by B. multivorans Y4. The results indicate that the No.22 consortium adapts well to different carbon sources through a change in its predominant species. This study provides some basic information regarding bioremediation using the consortium.