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Mycobacterium tuberculosis
*** Shopping-Tip: Mycobacterium tuberculosis
{{Taxobox
| color = lightgrey
| name = ''Mycobacterium tuberculosis''
| image = TB_Culture.jpg
| image_width = 200px
| image_caption = ''M. tuberculosis'' bacteria
| regnum =
Bacterium Bacteria
| phylum =
Actinobacteria
| ordo =
Actinomycetales
| subordo =
Corynebacterineae
| familia =
Mycobacterium Mycobacteriaceae
| genus = ''
Mycobacterium''
| species = '''''M. tuberculosis'''''
| binomial = ''Mycobacterium tuberculosis''
| binomial_authority = Zopf 1883
}}
'''''Mycobacterium tuberculosis''''' is the
bacterium that causes most cases of
tuberculosis[{{cite book | author = Ryan KJ; Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 | id = ISBN 0838585299 }}]. It was first described on
March 24,
1882 by
Robert Koch, who subsequently received the
Nobel Prize in physiology or medicine for this discovery in 1905. The ''M. tuberculosis''
genome has been sequenced
[{{cite journal
| author = Cole ST; Brosch R; Parkhill J; Garnier T; Churcher C; Harris D; Gordon SV; Eiglmeier K; Gas S; Barry CEIII; Tekaia F; Badcock K; Basham D; Brown D; Chillingworth T; Connor R; Davies R; Devlin K; Feltwell T; Gentles S; Hamlin N; Holroyd S; Hornsby T; Jagels K; Krogh A; McLean J; Moule S; Murphy L; Oliver K; Osborne J; Quail MA; Rajandream; M-A; Rogers J; Rutter S; Seeger K; Skelton J; Squares S; Squares R; Sulston JE; Taylor K; Whitehead S; Barrell BG.
| title = Deciphering the biology of ''Mycobacterium tuberculosis'' from the complete genome sequence.
| journal = Nature
| year = 1998
| volume = 393
| issue =
| pages = 537– 544
| url= http://www.nature.com/nature/journal/v393/n6685/full/393537a0_fs.html}}],[{{cite journal
| author = Camus JC; Pryor MJ; Medigue C; Cole ST.
| title = Re-annotation of the genome sequence of ''Mycobacterium tuberculosis'' H37Rv
| journal = Microbiology
| year = 148
| volume = 2002
| issue =
| pages = 2967–2973
| url= http://mic.sgmjournals.org/cgi/content/full/148/10/2967?view=full&pmid=12368430}}].
''M. tuberculosis'' is an
obligate aerobe mycobacterium (
Gram positive[While mycobacteria do not seem to fit the Gram positive category from an empirical standpoint (i.e. they do not retain the crystal violet stain), they are classifed as such due to their lack of an outer cell membrane.]) that divides every 16 to 20 hours. This is extremely slow compared to other bacteria, which tend to have division times measured in minutes (for example, ''E. coli'' can divide roughly every 20 minutes). It is a small, rod-like
bacillus that can withstand weak
disinfectants and can survive in a dry state for weeks but can grow only within a host organism.
''M. tuberculosis'' is identified microscopically by its staining characteristics: it retains certain stains after being treated with acidic solution, and is thus classified as an "
acid-fast bacillus" (AFB). In the most common staining technique, the
Ziehl-Neelsen stain, AFB are stained a bright red, which stands out clearly against a blue background. Acid-fast bacilli can also be visualized by fluorescent microscopy, and by
auramine-rhodamine stain. The reason for the acid-fast staining seen in mycobacteria is because of its thick waxy cell wall.
[{{cite book | author = Madigan, Michael; Martinko, John (editors) | title = Brock Biology of Microorganisms | edition = 11th ed. | publisher = Prentice Hall | year = 2005 | id = ISBN 0131443291 }}]
This waxy cell wall also is responsible for the typical caseous granuloma formation in tuberculosis. The component responsible is called the cord factor. ''M. tuberculosis'' bacteria are difficult to grow. Lowenstein-Jensen media have traditionally been used for this purpose, but faster results can now be obtained using Middlebrook media.
References
Category:Actinobacteria
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