RESUMEN
We have previously reported the disappearance of a specific strain degrading chlorobenzene from a functionally stable bioreactor. In the present work, we investigated this species succession and isolated a new dominant strain, identified as Pandoraea pnomenusa sp. strain MCB032. A specific 16S rRNA-targeted oligonucleotide probe was designed and validated to identify strain MCB032 using fluorescence in situ hybridisation (FISH). The results confirmed the presence of strain MCB032 in samples collected over time, and showed that it was primarily located within the biofilm. Denaturing gradient gel electrophoresis (DGGE) provided evidence that the species succession occurred early in the operating period. The application of these biomolecular tools highlighted the remarkable stability of this new strain during the 15 months of reactor operation. The succession was attributed to the competitive kinetic behaviour of strain MCB032, which exhibited faster growth (micro(max) = 0.34 h(-1)) and higher substrate affinity (K(s) = 0.35 mg L(-1)) than strain JS150. Finally, this study contributed to the characterisation of the recently established Pandoraea genus, an emerging group in the biodegradation field.
Asunto(s)
Reactores Biológicos/microbiología , Clorobencenos/metabolismo , Modelos Biológicos , Proteobacteria/citología , Proteobacteria/fisiología , Biodegradación Ambiental , Diferenciación Celular , Simulación por Computador , Proteobacteria/aislamiento & purificación , Especificidad de la EspecieRESUMEN
The availability of molecular probing technology in recent years has facilitated investigation of microbial community composition during bio-treatment of organic wastes. Particularly, it has allowed the study of microbial culture stability and correlation between stability and treatment performance. However, most studies to date have only addressed mixed cultures and there is limited information regarding single strain stability. Here we have investigated the microbial community dynamics in two bioreactors, each inoculated with a pure bacterial strain capable of degrading a recalcitrant substrate, namely Xanthobacter aut. GJ10 degrading 1,2-dichloroethane (DCE) and Burkholderia sp. JS150 degrading monochlorobenzene (MCB). Universal and strain specific 16S rRNA oligonucleotide probes were designed and used to follow strain stability. The bioreactor fed with DCE was functionally stable and the percentage of GJ10 cells in the community remained high (around 95% of total cells) throughout, even after introduction of foreign microorganisms. The bioreactor fed with MCB was also functionally stable, but in contrast to the DCE bioreactor, probing results revealed the disappearance of strain JS150 from the bioreactor within a week. The difference in behavior between the two systems is attributed to the specific pathway required to degrade DCE.