The human opportunistic pathogen, Pseudomonas aeruginosa PAO1, has been shown to kill the nematode Caenorhabditis elegans. C. elegans has been a valuable model for the study of bacterial pathogenesis, and has reinforced the notion that common virulence and host defense mechanisms exist. Recently, the pyrimidine pathway was shown to regulate virulence levels. Therefore, mutations in the pyrimidine pathway of PAO1 showed decrease virulence in the nematode. When starving the nematode, bacterial resistance was also shown to increase. It was hypothesized that starvation induced the DAF pathway, which regulates the transcription of genes involved with the antibacterial defense mechanism. Further research will be conducted to test this theory by performing RNAi experiments for the genes functioning in the antibacterial defense mechanism.

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The long held view of adherens junctions being a rigid complex has recently been questioned.  At the centre of this is α-catenin and the finding that it can not bind both β-catenin and actin simultaneously.  Isolation of a viable α-catenin mutant in the <i>C. elegans </i>homologue <i>hmp-1 </i>provided an excellent opportunity to study this dogma for the first time in a whole organism.  The work presented in this thesis aimed to characterise this mutation (<i>hmp-1(fe4)</i>) and isolate any potential suppressors of it.  On isolation of suppressors, these were used along with <i>hmp-1(fe4) </i>to investigate α-catenin/<i>hmp-1</i>s role at adherens junctions and how this overlaps with its role in regulating the actin cytoskeleton.  This study has demonstrated that a number of suppressors of <i>hmp-1(fe4) </i>do exist and that they are all intragenic.  In addition, the suppressors are capable of complementing a <i>hmp-1 </i>null strain in <i>hmp-1(fe4)</i>s absence.  Further analysis of these mutations by GFP labelling revealed that these mutations alter the proteins pattern of localisation.  It is thought that this alteration in localisation is the cause for the suppressor’s suppressive effect on <i>hmp-1(fe4).</i> Finally the characterisation of a random <i>C. elegans </i>mutant that arose from the <i>hmp-1(fe4)</i> study but was initially not related to it was later shown to have a synthetic lethal effect when in combination with <i>hmp-1(fe4) </i>and therefore a role that is dependent on a fully function α-catenin/<i>hmp-1.</i>