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R. Siddiqui F2013 Modified by DYH Mycobacterium tuberculosis General Characteristics: • • • Mycobacterium tuberculosis is the causative agent for the tuberculosis disease in humans. The bacterium is nonmotile and rod-shaped (bacilli). Facultative intracellular parasite, as well as an obligate aerobe – • • • • • • This can explain why tuberculosis is a disease that typically affects the lungs. Cell wall contains peptidoglycan and lipids, longchain alpha-alkyl, beta-hydroxy fatty acids. – Gram-stain and more Also contains mycolic acids, cord factor, and wax-D. Mycolic acids are significant for virulence in mycobacterium tuberculosis Cord Factor: winding-curved cording, toxic to mammals. Wax-D: located in the cell envelope (Kenneth 2008) • Mycobacterium tuberculosis is not considered gram-positive or gram-negative bacteria. However, the bacterium may weakly stain gram-positive when gram-stained. Mycobacterium tuberculosis is an acid-fast bacteria (can be impermeable to many stains and dyes). DNA Characteristics: -DNA found in macrophages, as well as phagocytic cells -posses many genes that contribute to base excision repair, nucleotide excision repair, recombination repair, etc. *These characteristics can explain why Mycobacterium tuberculosis is able to withstand environmental stresses, such as UV radiation. www.medschool.lsuhsc.edu/pathology/pathist/SURGPATH/special%20stai ns/assets/gram1.jpg R. Siddiqui F2013 Modified by DYH Mycobacterium tuberculosis Pathenogenesis: • • • • • Infection of host primarily in lungs. Once in the lungs, the bacteria are engulfed within alveolar macrophages, and remain in endocytic compartments where they mature to become phagosomes. The mycobacterium tuberculosis species are able to inhibit phagosome-lysosome fusion, thus preventing their destruction. Formation of granulomas allows infection o effectively remain in the lungs without dissemination. (Forrelad 2013) Invasins: • mce1A has been identified as a gene that plays a role in the invasion of nonphagocytic cells. • Cell wall proteins include the outer membrane proteins (OMPs). – play a role in adhesion, and invading the host cell. -OMPs also play a role in in degrading host structures. ****These are all factors that contribute to the species impermeability to stains and dyes, antibiotic resistance, resistance to lysis from host, etc. Virulence Factors: -Mycobacterium tuberculosis contain virulence genes that encode enzymes of many lipid pathways, cell surface proteins, and regulators and proteins of signal transduction systems (Forrelad 2013) -Additional virulence gene allows for survival of conditions inside host macrophages. http://stateschronicle.com/wpcontent/uploads/2013/09/Mycobacterium_tuberculosi s_14313982_1.jpg http://www.nature .com/news/2010/1 00609/images/new s.2010.TB.chest.xra y.jpg http://www.nimr.mrc.ac.uk/images/multimedia/research_group s/large/Davis-fig-1-full.gif