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Referenztyp Zeitschriften
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Titel (primär) Adaptive potential of alkaliphilic bacteria towards chloroaromatic substrates assessed by a gfp-tagged 2,4-D degradation plasmid
Autor Kiesel, B.; Müller, R.H.; Kleinsteuber, S.;
Journal / Serie Engineering in Life Sciences
Erscheinungsjahr 2007
Department UMB;
Band/Volume 7
Heft 4
Sprache englisch;
Keywords Bacteria; Biodegradation; Gen transfer; Pesticides
Abstract Chloroaromatics are important anthropogenic pollutants in many environmental systems. Knowledge on the microbial detoxification potential of such compounds in extreme environments is still limited. In pristine environments, horizontal gene transfer is the major mechanism for the adaptation of microbial communities to xenobiotic substrates. However, gene transfer mediated by plasmid conjugation from bacteria living in moderate environments to those thriving in extreme habitats might be limited by different growth requirements of donor and recipient cells. In order to assess the potential of alkaliphilic bacteria from a pristine ecosystem to adapt to chloroaromatic compounds, the host range of the 2,4-D degradation plasmid pJP4 and the expression of the degradation pathway in alkaliphilic bacteria isolated from soda ponds in the South-Hungarian Lowlands were investigated. Since most antibiotics are unstable under alkaline conditions, the Green Fluorescent Protein was used as a selective marker for monitoring plasmid transfer. The plasmid pJP4 was tagged by a Tn5::gfp cassette outside the catabolic region. The cassette was inserted into the korB gene without affecting replication, partitioning and transfer functions of pJP4. Escherichia coli was used as a donor of the gfp-tagged pJP4, as its pH tolerance is higher than that of the natural host Cupriavidus necator  JMP134. Additionally, alkaliphilic transconjugants were used as donors in a second mating experiment to enable plasmid transfer at higher pH values. Phylogenetic identification of transconjugants by 16S rRNA gene sequencing revealed that the host range of pJP4 among alkaliphilic bacteria comprises the proteobacterial genera of the β-subdivision (Ralstonia), the γ-subdivision (Pseudomonas, Halomonas, Idiomarina and other genera belonging to the Alteromonadales), the α-subdivision (Devosia) and even the Gram-positive bacteria of the genus Alkalibacterium (Firmicutes). While the majority of the transconjugants were unable to degrade 2,4-D to a significant extent, five isolates identified as Halomonas sp. degraded 2,4-D and 3-chlorobenzoate in the presence of an additional carbon source but were unable to grow on chloroaromatics as the sole carbon and energy source. Enzyme assays after chemostat cultivation revealed that the degradation of chloroaromatics is limited by the low activity of chloromuconate cycloisomerase. The results indicate that the host range of plasmid pJP4 is broader than the range of bacteria capable to express the 2,4-D degradation trait and that the Halomonadaceae are potential hosts to establish degradative traits for chloroaromatics in alkaline environments.
ID 16091
dauerhafte UFZ-Verlinkung
Kiesel, B., Müller, R.H., Kleinsteuber, S. (2007):
Adaptive potential of alkaliphilic bacteria towards chloroaromatic substrates assessed by a gfp-tagged 2,4-D degradation plasmid
Eng. Life Sci. 7 (4), 361 - 372