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BSc Researches

  • MsC in Systems and Synthetic Biology Research project

In order to complete my master in Systems and Synthetic Biology, I've spend 7 months at the University of British Columbia (Vancouver, Canada) working in Professor Beatty's lab on Rhodobacter Capsulatus.

Title: Relation between transduction by Gene Transfer Agent of Rhodobacter Capsulatus and sub-inhibitory concentration of antibiotics


Abstract: Rhodobacter capsulatus is a Gram negative metabolically versatile a-proteobacteria producing a bacteriophage-like particle called gene transfer agent (GTA) but does not cause any observable lysis. Rhodobacter capsulatus gene transfer agent (RcGTA) is involved in horizontal gene transfer (HGT) by packaging random 4.5 kb fragments bacterial genomic DNA and is in consequence capable of transducing a recipient R. capsulatus cells. It has been shown recently that sub-inhibitory concentrations of aminocoumarins increase transduction frequency caused by Rhodobacter capsulatus gene transfer agent (RcGTA) but the mechanisms leading to this increase are still unknown. Using an improved transduction assay, the increase of the frequency of gene transfer has been quantified for the two aminocoumarins novobiocin and clorobiocin. A transduction assay using a transwell plate gave us information regarding the direction of the gene transfer, which appear to be going only in one direction with the two strains used during the study. Based on the bibliography a mutation in the gyrase B coding sequence has been done in order to provides a resistance to aminocoumarins and more particularly to novobiocin. Finally, the effects of aminocoumarins on R. capsulatus were studied by using a fluorescent mutant and flow cytometry and taught us that after a long time of growth with novobiocin, R. capsulatus present a slightly higher level of transcription of the RcGTA gene cluster. The results of these research suggest that aminocoumarins have a slight effect on the RcGTA production but can’t explain alone such a high increase in the gene transfer and the study of the mutant resistant to aminocoumarins will provide more information about their effects.

  • BsC Research project

While I was exchange student at the University of Calgary during the year 2012-2013, I did a research project in Professor Hynes's Lab under the supervision of Dr Halmillawewa.

Title: Characterization of Mesorhizobium loti bacteriophages

Abstract: Phage collection of Dr Hynes Lab contains isolates from different soil samples from western Canada.The collection contains rhizobiophages that have been trapped using different strains of rhizobia and some of these phages have been subjected to genomic and phenotypic characterization. As a part of this ongoing project, some phages that show distinct plaque morphologies were isolated using Mesorhizobium loti as the trapping host. The objectives of the work described in this report were to isolate phages with a different plaque morphology that infect Mesorhizobium spp. and to characterize theses phages by following and improving the molecular and microbiological techniques already used in the Hynes lab.

Poster:
  • Halmillawewa, A., Restrepo, M., Gavard, R., Ganesan, S., Yost, C. K., Hynes, M. F. (2013). “Genomic and phenotypic characterization of novel bacteriophages infecting rhizobia.” Poster presented by Halmillawewa A. at 20th Evergreen International Phage Biology Meeting (Aug. 4-9, 2013), The Evergreen State College, Olympia, Washington, USA.
Presentation:

April 2013: Seminar; Biological Sciences Student Symposium, University of Calgary.
"Characterization of Mesorhizobium loti bacteriophages"