Miss Gugu Kubheka
MSc Student
Bacteria Genomics and Plant Pathogen Interactions
Research Interests
Pectobacterium subsp. carotovorum brasilienses (Pcb) is an economically devastating potato (4th largest crop in the world) pathogen in South Africa, causing the soft rot and blackleg diseases. Pcb was recently distinguished from the more common P. atrosepticum (Pca) as the causal agent in Brazil due to its ability to grow at 37°C and other genetic distinguishments to the other pectobacteria strains/spp. The similarity of the climatic conditions between Brazil and South Africa led to Pcb being identified as the actual potato pathogen in South Africa. There is very little known about Pcb because of its recent discovery. This includes its pathogenesis, which is a very significant aspect especially when looking at the economically devastating effects of this pathogen in South Africa. The title of my thesis is ‘Characterisation of the virulence mechanisms in Pectobacterium carotovorum subsp. brasiliensis: colonisation and transcriptome profiling’ and the aim of my project is thus to characterise Pcb in terms of its virulence.
The first objective is to investigate the infection and colonization processes used by Pcb and this will be expanded to include its dissemination within and between plants and consequently its disease cycle. Fluorescent protein tagging systems will be used to tag Pcb and enable us to trace/track its migration within the potato plant as well as between potato plants (in soil, water, etc.). We have decided on two potential flourecent markers; eGFP and mCherry, which will also aid in potential future comparative studies between strains or species when used together. The end result will be the development of a fluorescent protein tagging system specific to Pectobacteria spp. as well as to facilitate the development of control strategies to manage this pathogen against potatoes. The second objective is to investigate the virulence mechanisms induced and the points of infection at which they are expressed. These experiments will be done in vitro with the aid of different media (with/without plant extracts) to simulate different environmental conditions. The transcriptome profiling will be facilitated by cDNA-AFLP and confirmed by real-time RT-PCR. We expect this section of the study to indicate to us the more significant factors that make Pcb so devastatingly pathogenic and provide targets for future works in understanding each of their roles in virulence.
