<p>The Streptococcus Milleri/Anginosus group (SMG) includes Streptococcus anginosus, Streptococcus constellatus and Streptococcus intermedius. The SMG is found in healthy individuals but these bacteria are most known clinically for being associated with invasive disease and more recently, airway infections including cystic fibrosis (CF). The SMG like many other streptococci are naturally competent, being able to actively bind, uptake and integrate extracellular DNA. Competence regulation involves a competence-stimulating peptide (CSP) derived from the ComC precursor and a two- component signaling system (a histidine kinase ComD and its response regulator ComE). In this study, I examined the distribution of CSP/ComD sequences and competence in 170 SMG clinical isolates from CF airways and invasive disease. Five predicted CSP sequences were observed; one represented a newly predicted CSP and two arose from frameshift mutations in comC and appeared to be non-functional. The three CSPs fall into two functional groups that do not cross-activate due to receptor specificity. In addition, I observed that the Streptococcus constellatus subspecies pharyngis strains could not be transformed. However, I demonstrated that the pharyngis strains possess a functional ComCDE pathway, suggesting that the CSP regulates genes other than those involved in natural transformation. For many strains, I observed high endogenous competence levels that were only marginally induced by added peptide. These strains appear to be constitutively competent during exponential growth. The high basal level of expression and the heterogeneity in the SMG competence systems could impact how the SMG evolve during colonization and infections and specifically acquire antibiotic resistance and virulence genes.</p> / Master of Science (MSc)

The taxonomic status of its 59 nominal species of the genus Bothus (Pleuronectiformes: Bothidae) has been revised, based on a morphological study of 320 type and non-type specimens. Of the 59 nominal species examined in the study, 18 have found to be valid and are re-described. The genus Bothus (pro parte) is considered natural on the basis of two characters previously identified by Hoshino and Amaoka (2006): a ventral expansion of the haemapophyses of the precaudal vertebrae and the bony expansion of the haemal spine of the first caudal vertebrae. These characters were observed in all accepted species of Bothus, excluding B. swio. The morphology of B. swio overlaps with other bothid genera, but its generic placement was not analysed. Engyrprosopon and Crossorhombus are hypothesized as outgroups of Bothus based on the character state identified by Hoshino and Amaoka (2006), an anterior extension of the sciatic part of the urohyal past the main part of the urohyal. A phylogenetic analysis of the Bothidae is needed to substantiate this hypothesis of relationship, to validate the monophyly of Bothus and to resolve the generic position of B. swio. The geographic distribution of each species is mapped and an up-to-date species identification key has been created. The 18 valid species are as follows, with their synonym species in parenthesis: Bothus assimilis, Bothus constellatus, Bothus ellipticus, Bothus guibei (Rhombus heterophthalmus), Bothus leopardinus, Bothus lunatus, Bothus maculiferus, Bothus mancus (Pleuronectes barfi, Rhombus macropterus), Bothus mellissi, Bothus myriaster (Citharicthys aureus), Bothus ocellatus (Platophrys nebularis, Rhomboidichtys spinosus, Rhombus bahianus), Bothus pantherinus, Bothus podas (Bothus rumolo, Bothus tappa, Rhombus gesneri), Bothus robinsi, Bothus swio, Bothus thompsoni, Bothus tricirrhitus, and Bothus ypsigrammus.