The aim of this work was to study spatial evolution of the chemotaxis proteins of a group of plant-associated soil-dwelling bacteria vernacularly referred to as the B. subtilis group. This was achieved by creating homology models for the chemotaxis proteins if a suitable template was available, and by analysing the selective forces (positive, purifying or neutral) acting upon the chemotaxis proteins. Chemotaxis is the phenomenon in which bacteria direct their movement towards more favourable conditions, and is critical for processes such as obtaining nutrients, escaping toxic compounds, host colonization and bio-film formation. Members of the B. subtilis group exhibit different preferences for certain host plants, and it is therefore feasible that their chemotactic machinery are fine-tuned to respond optimally to the conditions of the various niches that the strains inhabit. Homology models were inferred for the plant growth promoting B. amyloliquefaciens FZB42 proteins CheB, CheC, CheD, CheR, CheW and CheY. The interactions between: CheC-CheD, the P1 and P2 domains of CheA with CheY and CheB, and the P4 and P5 domains of CheA with CheW were also modelled. The hydrophobic interactions contributing to intra- and inter-protein contacts were analysed. The models of the interactions between CheB and the various domains of CheA are of particular interest, because to date no structures have been solved that show an interaction between a histidine kinase (such as CheA) and a multidomain response regulator (such as CheB). Furthermore, evidence that phospho-CheB may inhibit the formation of phospho-CheY by competitively binding to the P2 domain of CheA is also presented. Proteins were analysed to determine if individual amino acid sites are under positive, neutral or purifying selection. The Methyl Accepting Chemotaxis Proteins (MCPs), CheA and CheV were also analyzed, but due to a lack of suitable templates, no homology models were constructed. Site-specific positive and purifying selection were estimated by comparing the ratios of non-synonymous to synonymous substitutions at each site in the sequences for the chemotaxis proteins as well as for the receptors McpA, McpB, and McpC. Homology models were coloured according to intensity of selective forces. It was found that the chemotaxis proteins of member of the B. subtilis group are under strong evolutionary constraints, hence it is unlikely that positive selection in these proteins are responsible for the differences in habitat preference that these organism exhibit.

This investigation deals with the study of the possible antibiotic effect of oleoresins of one hundred common Texas plants upon twenty-five gram-negative bacterial organisms.

Tuberculosis (TB) still remains a health problem globally with over a million new infections and a mortality rate of 1.5 million individuals annually (Hawn et al., 2014). The emerging multi-drug resistant (MDR) strains that accompany human immune deficiency virus (HIV) infection in high-incidence populations contribute significantly to the health burden of TB (Areeshi et al., 2014). The standard treatment that is advocated by the World Health Organization (WHO) for active tuberculosis includes long-term therapy that incorporates the use of isoniazid, rifampicin, pyrazinimide and ethambutol as front line drugs (WHO, 2013). Drug resistance against established treatment options for TB makes research into new forms of therapy an imperative in health care (Ntulela et al., 2009). South Africa is currently witnessing a high number of cases of drug-resistant TB. In some parts of the country, one in ten cases of TB is resistant to treatment. It is therefore essential to have new anti-tuberculosis agents, which can be readily and simply produced from some local source (Warner et al., 2014). A logical starting point for this research of new agents would be the herbal medicines which have been used for centuries in rural areas by local healers. Western developed countries have harvested ethno botanical knowledge and have produced drug therapies for conventional medicines for other ailments. The activity of extracts of the active plants and their properties still require study in animal models in order to assess their future as new anti-tuberculosis agents (Lall and Meyer, 1999). This study focuses on qualitative and quantitative experimental findings after the administration of a medicinal plant extract to animals. This will include daily observation of animals, recording of feed consumption, recording of animal weights, macroscopic examination of animals at necropsy, tissue harvesting, histological procedures and microscopy.