Molecular Virology
Mycoviruses
While viruses have long been recognised as important components of all biosystems, viruses of fungi (mycoviruses) have been largely ignored and, apart from a few notable exceptions, their roles in fungi are largely unknown. Following on from studies on the molecular characterisation of a number of mycoviruses found in plant pathogenic fungi we are investigating novel double-stranded (ds) RNA elements in Phleibiopsis gigantea, a fungus used for biological control of sap staining in wood, a collection of wild Saccharomyces paradoxus yeast strains, and several species of Aspergilli, especially Aspergillus fumigatus.
The filamentous fungus Aspergillus fumigatus is the worlds leading cause of mould-related fatality, mostly resulting from invasive pulmonary aspergillosis in immune-deficient patients. The pathogen also provokes severe allergic disease in asthmatics, and colonises cystic fibrosis patients, therefore posing a significant clinical burden. We have recently discovered that several clinical isolates of Aspergillus fumigatus harbour at least two dsRNA mycoviruses. Whilst dsRNA elements have been described in other members of the Aspergilli this is the first report of the existence of dsRNA elements in this clinically important species.
Currently we do not know the role or function of these mycoviruses in the fitness or pathology of Aspergillus fumigatus and to understand more of these aspects we are cloning and sequencing the dsRNA genomes of both genomes, in an effort to determine relationships with known mycoviruses and to investigate if the elements are ubiquitous in other clinical isolates of the fungus. To this end we are screening as many isolates of the fungus as possible to determine any collative effects on fitness and pathogenicity. We are extending these investigations to other clinically important Aspergillus spp. Including Aspergillus versicolor, Aspergillus terreus and Aspergillus flavus. We intend to construct and use full-length clones of these mycoviruses for use in gene silencing technology which is currently under developed in fungi.
Molecular Microbiology
Bacterial pathogenicity and bioremediation
Members of the Burkholderia cepacia complex (Bcc) are important clinically as opportunistic pathogens of cystic fibrosis (CF) patients and are useful for bioremediation of soils and biocontrol. In previous investigations of environmental isolates of Burkholderia species we identified a novel clade of organisms with potential as bioremediation agents and are keen to investigate their capacities in this area of research. In a new project we have developed a gene knockout system for the sigma factor RpoN (σ54) of Burkholderia cenocepacia and Burkholderia xenovorans strain LB400. The procedure developed has general utility for other genes and resulting mutants can be complemented with wild type genes. Since RpoN has an important role in many major adaptive responses in bacteria and is involved in various physiological responses, such as pathogenesis, quorum sensing and bioremediation we are interested in the effects of RpoN and its associated activator genes on these processes in the type strains and our collection of novel isolates of the Bcc.
Reference
RpoN is involved in motility and is essential for nitrate utilisation in Burkholderia cepacia J2315. Yu, M., Buck M. & Coutts R.H.A. FEMS Microbiology Letters (2009; In press).
Coutts laboratory; Late September 2008
Back row: Noor Nordin (Faizul); Muhammad Bhatti (Faraz); Dr Robert Coutts; Atif Jamal;
Front row: Xiyu Phoon (Xi); Dr Zisis Kozlakidis (Z); Noemi Herrero Asensio; Mahsan Nemet-Bakhsh
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