| Summary: | The aims of this thesis were to investigate the biological properties of both clinical and environmental isolates of the <i>B. cepacia </i>complex, with particular relevance to their pathogenicity and potential biotechnological exploitation. <i>B. vietnamiensis </i>were more sensitive to ceftazidime and chloramphenicol than strains from the other genomovars, and environmental <i>B. cepacia </i>genomovar III strains were more sensitive to ciprofloxacin and chloramphenicol than clinical isolates of the same genomovar. Although resistance to antibiotics is not uniform across all the subgroups of the <i>B. cepacia </i>complex, the antibiotic-sensitive strains can readily mutate to high levels of resistance. With the exception of catalase and melanin that were only produced by clinical strains, other putative virulence factors were detected in both clinical and environmental isolates. Certain factors including genetic markers for epidemic spread, were also detected in candidate biopesticide strains. The phytopathogenicity of clinical and environmental isolates was also found to be similar. Lack of knowledge regarding the fate of the <i>B. cepacia </i>complex strains introduced to the environment is a major obstruction to the organisms' commercial exploitation. Of major concern is the possibility of genetic exchange between different <i>B. cepacia </i>complex strains had between the <i>B. cepacia </i>complex and other soil microflora. Natural transformation of <i>B. cepacia </i>complex strains was demonstrated with DNA from the well-characterised epidemic lineage ET12, represented by the Edinburgh isolate J2315. The transformed bacteria included candidate biopesticide strains. The similarity of putative <i>B. cepacia </i>complex virulence factors produced by clinical, environmental and candidate biopesticide strains, as well as the natural exchange of genes between all subgroups suggests that caution should be exercised on the commercial application of members of the <i>B. cepacia </i>as biopesticides.
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