07/2009 - Prof. Dr. Gabriele Diekert
Expression control and biosynthesis of dehalogenating enzymes
from anaerobic soil bacteria in response to the interaction with
aerobic halogenating fungi
Abstract
The research in our group is focused on the elucidation of the
interaction between aerobic, lignin-degrading fungi and
anaerobic bacteria in the course of halogenation and
dehalogenation of organic compounds at the oxic/anoxic
interface. Lignin-degrading fungi of boreal forests show the
ability to produce chlorinated organic compounds while growing
on wood. Chlorinated organic compounds can be subsequently
dechlorinated under anoxic conditions by a heterogeneous group
of soil bacteria (Firmicutes, Proteobacteria). The key
enzymes of the anaerobic dechlorination are the B12-dependent
reductive dehalogenases. It was shown very recently that the
expression of the dehalogenase-related genes is controlled by
the absence or presence of the respective chlorinated substrate
in a novel type of long-term regulation.
To examine the functionality of this special microbial food
chain three major issues will be studied in more detail: (i) the
ecological niche of dechlorinating bacteria in forest soil with
respect to hot spots of lignin-degradation will be
characterized, (ii) the induction of the reductive dehalogenase
gene expression in response to the occurrence of chlorinated
organic compounds formed upon fungal lignin-degradation will be
investigated, and (iii) the molecular mechanism of the signal
transduction from substrate recognition to dehalogenase gene
expression will be studied. Established techniques for the
investigation of the tetrachloroethene (PCE, perchloroethylene)
reductive dehalogenase found in Desulfitobacterium spec.
will serve as basis for the identification and characterization
of protein factors necessary for the adaptation of the bacterial
cells to changes in environmental conditions.
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