Deterministic selection of phenol-degrading populations in laboratory scale bioreactors

BASILE LA, ERIJMAN, L.

Cairns

Congreso; XII International Symposium on Microbial Ecology (ISME 12); 2008

ISME

With the aim of testing the variability of the functional diversity and activity within specialized bacterial communities, we carried out a quantitative analysis of the diversity of phenol hydroxylase gene (LmPH, a surrogate measurement of phenol-degrading population size) in replicated phenol degrading-laboratory scale activated sludge reactors. Eight specific sets of LmPH primers were developed to target groups with a genetic distance of 0.07, which likely represent ecologically relevant variants of the enzyme. The primers were used to follow the dynamics of LmPH gene diversity, using real time PCR assays throughout nine months of bioreactors operation. We rejected the null hypothesis that the total abundance of LmPH genes is an indicator of phenol degradation rates irrespective of functional diversity (LmPH genes). Rather, a significant increase in phenol-degrading activity in the phenol-amended sludge was accompanied by a parallel increase in LmPH gene diversity. In a separate round of experiments phenol concentration was increased stepwise along a period of four months of operation up to a concentration of 1875 mg phenol.L-1.d-1. We found a replicable coexistence of redundant species, with their relative abundance determined by the concentration of phenol in the feed. We conclude that in the absence of immigration, niche differentiation has a strong influence in the assembly of phenol-degrading communites.