INVESTIGADORES
BASILE Laura Ana
congresos y reuniones científicas
Título:
Niche oriented selection of phenol-degrading populations in bioreactors
Autor/es:
BASILE LA, ERIJMAN L.
Lugar:
Rosario
Reunión:
Congreso; V Congreso Argentino de Microbiología General - SAMIGE; 2008
Institución organizadora:
SAMIGE
Resumen:
The distribution and abundance
of species have important implications for the functioning and stability of
many ecosystems. Here we test the variability of the functional diversity of an
activated sludge acclimated to degrade of phenol, by following the dynamics of
the gene coding for the multicomponent phenol hydroxylase (LmPH) as a function
of the concentration of phenol in the feed. LmPH catalyzes the conversion of
phenol to catechol, the rate-limiting step in the phenol degradation pathway in
the environment.
Two lab-scale activated sludge
systems specialized in phenol degradation were subjected to a gradual increase
in phenol load. Two libraries of LmPH gene were constructed at different times
of reactor operations. Aminoacidic-derived sequences of a total of 124 clones
were separated into seven groups with a phylogenetic distance of 0.12, which
likely represent ecologically relevant variants of the enzyme. Seven specific
sets of LmPH primers were used to follow the dynamics of LmPH gene diversity,
using real time PCR assays at 6 different times corresponding to different
loads of phenol, from 100 to 1500 mg/L. The same sets of primers were used for
the quantification of LmPH variants in two control reactors, which were
maintained with a constant phenol concentration of 100 mg/L. We found a
replicable coexistence of redundant species, with their relative abundance
determined by the concentration of phenol in the feed. Comparison of the
abundance patterns of phenol-degrading species suggests a considerable degree
of determinism, where phenol-degrading populations are recruited from the
existing pool, each with their particular ecological traits that determines their
relative abundance in the community. We conclude that in the absence of
immigration, niche differentiation has a strong influence in the assembly of
phenol-degrading communites.
To test this prediction we
pursued the isolation of representatives of bacteria containing each of the
different detected LmPH gene. Thirteen isolates were obtained using a wide
range of culture conditions, finding at least one representative of six of the
seven populations. These isolates are currently being characterized for their
kinetics properties of phenol degradation and for their kinetics of growth and
inhibition by phenol.
