My.co.bac.te'ri.um. Gr. n.
mukês
a fungus; L. neut. n.
bacterium
, a small rod; N.L. neut. n.
Mycobacterium
a fungus rodlet.
Actinobacteria / Actinobacteria / Corynebacteriales / Mycobacteriaceae / Mycobacterium
Aerobic to microaerophilic
,
slightly curved or straight rods
(0.2–0.6 × 1.0–10 µm),
which are acid–alcohol‐fast at some stage of growth
. Most species are difficult to stain by Gram's method, but are usually considered Gram‐stain‐positive. Branching may sometimes occur and a filamentous or mycelium‐like growth may appear which, on slight disturbance, becomes fragmented into rods or coccoid elements.
Cells are nonmotile and asporogenous
;
conidia or capsules are not produced
;
there are no grossly visible aerial hyphae
.
Colonies may be white‐ to cream‐colored
;
some strains produce yellow‐ or orange‐pigmented colonies with or without light stimulation
.
Whole‐organism hydrolysates are rich in
meso
‐diaminopimelic acid
,
arabinose
,
and galactose
.
The peptidoglycan is of the A1γ type
.
Muramic acid moieties are
N
‐glycolated
.
Cells and cell walls are rich in lipids
.
These include waxes which have characteristic
,
chloroform‐soluble
,
mycolic acids with long
(
60–90 carbon atoms
)
branched chains
.
The fatty acid esters released on pyrolysis MS of mycolic acid esters have 22–26 carbon atoms
.
Cells contain diphosphatidylglycerol
,
phosphatidylethanolamine
,
phosphatidylinositol
,
and phospatidylinositol mannosides as predominant polar lipids
,
straight‐chain saturated
,
unsaturated
,
and 10‐methyloctadecanoic
(
tuberculostearic
)
fatty acids as major fatty acid components
,
and dihydrogenated menaquinones with nine isoprene units as the predominant isoprenolog
. The genus includes obligate parasites, saprophytes, and opportunistic forms.
DNA G
+
C content
(
mol
%): 57–73 (
T
m
; HPLC; whole‐genome sequencing).
Type species
:
Mycobacterium tuberculosis
(Zopf 1883) Lehmann and Neumann 1896, 363
AL
.
