They are not bacteria Microbiology 3 - Mycobacteria You find mycobacteria everywhere - they cause a lot of disease - Unicellular, rod shape - Hydrophobic - they clump together - Obligate aerobes o Can survive in anaerobic condition o Non-capsulated, non-sporulating o 2-4um length x -0.2-0.5 um width They extend from the poles and septate in the middle o They are slightly ruffled on the outside - very lipid rich cell wall - Many species of mycobacterium exist; only a few cause diseases in human o Phylum: actinobacteria (high G+C content) Filamentous, see them in filaments when viewing them o Family - mycobacteriaceae o Genus - Mycobacterium - Many important species are SLOW GROWING E.g. tuberculosis - doubling time of 24 hours - Cell wall has HIGH LIPID CONTENT o Makes them hydrophobic so you have to use special media to stop them from coupling o E.g. detergent - They are neither gram positive nor gram negative classically o But the stain will show a gram positive surface proteins phospholipid 8 - teichoic acid 8 lipoteichoic acid peptidoglycan NAM NAG peptide cytoplasmic membrane Gram-Positive Cell Wall protein phospholipid LPS O polysaccharide ·lipid A outer membrane lipoprotein peptidoglycan cytoplasmic membrane Gram-Negative Cell Wall Cell Wall - Unlike either the gram-positive or gram-negative cell wall - Complex arrangement of various different levels o Inner membrane o Periplasmic space Leafleted with lipoarabinomannan (LAM) . Towards the end you have the LAM anchored to a peptidoglycan layer o Arabinogalactan - peptidoglycan (AGP) layer
o Outer free lipids that contain mycolic acid (unique to mycobacteria) - 60% lipid - Major component: mycolic acid - Other important lipids; o TDM (trihalosedimycolate) · Trihalose (a sugar) . Two mycolic acid groups · Adds intracellular survival, stops the lysosome from fusing to the phagosome which would destroy the bacterial cell Surface acyl lipids o LAM o Phosphatidylinositol mannosides (PIM) - Has a lot of resistance o Heat, desiccation, UV light, antibiotics - Own designation; ACID-FAST - Special stains are required to see them Ziehl-Neelson Stain - Stain with a hot concentrated solution of carbol fuchsin o All bacterial cells will stain pink - De-stain with acid-alcohol mix o Hydrochloric acid / ethanol OR 20% H2SO4 o That's why it's called an acid-fast microorganism o Mycobacterial cells remain pink - Counterstain with methylene blue for all the other cells Infections: Species of Mycobacteri um M. tuberculosis M. bovis M. avium intracellulare M. leprae Disease Tuberculosis (TB) Tuberculosis (TB); acquired from consumption of unpasteurised milk Disseminated TB in immunocompromi sed patients eg. HIV Leprosy Folded lesions on face and limbs, Symptoms Often asymptomatic; pneumonia-like presentation (weight loss, temperature, cough, blood in sputum) As above Lung infection and spread to bones, joints, blood, renal system, meninges; frequently results in death
(Hansen's bacillus) disfiguration, loss of peripheral nerves, secondary infection Tuberculosis; The Beginnings - 1720: Benjamin Marten described as 'consumption' - 1882: cause of consumption was discovered by Kosch - 21st Century: TB DNA identified in Granville's Mummy 21st Century Tuberculosis -