Maintenance of phenol-hydroxylase genotypes at high diversity in bioreactors exposed to step increases in phenol loading

LAURA A. BASILE; LEONARDO ERIJMAN

FEMS MICROBIOLOGY ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2009

0168-6496

To better understand how the composition of bacterial communities changes in response to different environmental conditions, we examined the influence of increasing phenol load on the distribution of the protein-coding functional gene of phenol hydroxylase (LmPH) and of the 16S rRNA gene in lab-scale activated sludge reactors. LmPH diversity was initially assessed from a total of 124 clone sequences retrieved from two reactors exposed to low (0.25 g.l-1) and high (2.5 g.l-1) phenol concentration. The quantitative changes in the concentration of the eight detected genotypes accompanied changes in the phenol degradation rates, indicating a community structure-function relationship. Nonmetric dimensional analysis showed that LmPH genotypes and the DGGE banding patterns clustered together by phenol concentration, rather than by reactor identity. Seven isolates, representing cultivated strains of each of the observed LmPH genotypes, exhibited a rather narrow range of physiological diversity, in terms of growth rate and kinetic parameters of the phenol-degrading activity. We suggest that lab-scale reactors support many ecological niches, which allow the maintenance of a high diversity of ecotypes through varying concentration of phenol, but the ability of particular strains to become dominant members of the community under the different environmental conditions are not easily predicted solely from their phenol-degrading properties.