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GENOME ANALYSIS OF BURKHOLDERIA CEPACIA AC1100
Citation:
Hendrickson, W., A. Hubner, A. KavanaughBlack, AND R. Edelstein. GENOME ANALYSIS OF BURKHOLDERIA CEPACIA AC1100. Presented at Biotechnology Risk Assessment Symposium, Pensacola, FL, June 06 - 08, 1995.
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Presentation
Description:
Burkholderia cepacia is an important organism in bioremediation of environmental pollutants and it is also of increasing interest as a human pathogen. The genomic organization of B. cepacia is being studied in order to better understand its unusual adaptive capacity and genome plasticity. We are studying the diversity of chromosome number and size, and genome organization among different B. cepacia isolates. Large replicons of several environmental and clinical isolates range in size from 0.3 to 5.3 million bp and vary in number from two to five. Strain AC1100 is of interest because it was isolated after selection for degradation of the herbicide 2,4,5-T. This strain contains four replicons of 0.34, 0.53, 2.7 and 4.0 Mbp. Genes coding for the enzymes required for the first step and for late steps in the degradative pathway were previously cloned. We have mapped the tft A gene to the 0.34 Mbp replicon and the tftE-H cluster to the 0.53 Mbp replicon. The data suggest that the 2,4,5-T pathway may have evolved by separate translocation events into each of the replicons. In the absence of 2,4,5-T, the genes are rapidly lost, most often by deletion and translocation events. Transposon mutagenesis has been used to create amino acid auxotrophs as well as new 2,4,5-T mutants to identify the remaining genes of the pathway. Using a cosmid bank of AC1100, a genetic and physical map of the strain is being constructed that can be used to compare B. cepacia strains in more detail. IS elements containing outwardlly oriented promoters were isolated from AC1100 using a promoter trap plasmid system. PCR analysis of the transposition products showed that two IS elements were responsible for most events. These elements could drive high level gene expression from as much as 600 base-pairs upstream of the gene. The IS elements are found near the tft genes, suggesting that they may play a role in the evolution of the pathway as well as the instability of the genes.