Evaluation of the role of Mycobacterium tuberculosis pili (MTP) as an adhesin, invasin, and cytokine inducer of epithelial cells

Abstract This study was undertaken in order to assess the involvement of Mycobacterium tuberculosis pili (MTP) as an adhesin, invasin, and cytokine inducer in the M. tuberculosis-epithelial cell interaction. A MTP-deficient strain of M. tuberculosis demonstrated a significant reduction of 69.39% (p = 0.047) and 56.20% (p = 0.033) in its ability to adhere to and invade A549 pulmonary epithelial cells, respectively, in comparison with the wild-type strain. Complementation of the MTP-deficient mutant restored its adhesion and invasion capacity back to the wild-type levels. Overall, it was found that similar concentrations of IL-1β, IL-4, IL-6, IL-8, G-CSF, IFN-γ, MCP-1, and TNF-α were induced in A549 cells infected with the MTP-proficient and MTP-deficient strains. However, at 48 h post-infection, the MTP-deficient mutant induced significantly lower levels of TNF-α than the wild-type strain (p = 0.033). Furthermore, at 72 h post-infection, the mutant induced significantly higher levels of IL-8 than the wild-type (p = 0.005). We conclude that MTP is an adhesin/invasin of epithelial cells and, while playing a role in M. tuberculosis entry, they do not appear to largely influence the epithelial cell cytokine response.

Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast density

Production of good quality beer is dependent largely on the fermentation temperature and yeast strains employed during the brewing process, among others. In this study, effects of fermentation temperatures and yeast strain type on beer quality and spent yeast density produced after wort fermentation by two commercial yeast strains were investigated. Beer samples were assessed for colour, clarity and foam head stability using standard methods, whilst the compositions and concentration of Beer Volatile Compounds (BVCs) produced were assessed using GC-MS. The spent yeast density, measured as dry cell weight, ranged between 1.84 - 3.157 mg/ml for both yeast strains with the highest yield obtained at room temperature fermentation. A peak viable population of 2.56 x 10(7) cfu/ml was obtained for strain A, also during fermentation at room temperature. The foam head of the beers produced at 22.5ºC was most stable, with foam head ratings of 2.66 and 2.50 for yeast strain A and B, respectively. However, there was no significant (p = 0.242) difference in colour intensity between the beers produced at the different fermentation temperatures. Eight different BVCs were detected in all beer samples and were found to affect the organoleptic properties of the beer produced. Further optimizations are required to determine the effects of other parameters on beer quality.

Visualisation of the microbial colonisation of a slow sand filter using an Environmental Scanning Electron Microscope

The removal of contaminants in slow sand filters occurs mainly in the colmation layer or schmutzdecke - a biologically active layer consisting of algae, bacteria, diatoms and zooplankton. A ripening period of 6 - 8 weeks is required for this layer to form, during which time filter performance is sub-optimal. In the current study, an environmental scanning electron microscope was used to visualise the ripening process of a pilot-scale slow sand filter over a period of eight weeks. To achieve this, sand particles were removed at weekly intervals and observed for biofilm development. Biological mechanisms of removal in slow sand filtration are not fully understood. A visualisation of the colonisation process would enhance the knowledge and understanding of these mechanisms. Colonisation of sand particles and increase in biomass was clearly seen during the ripening period. The mature, ripened filter exhibited a dense extracellular matrix consisting of a wide variety of microorganisms and their extracellular and breakdown products. This research demonstrated the successful use of an environmental scanning electron microscope to visualise the complex, heterogeneous nature of the schmutzdecke in a slow sand filter. Such knowledge could possibly lead to an increase in the application of slow sand filtration, especially for rural communities.