The role of trehalose dimycolate (cord factor) on morphology of virulent M. tuberculosis in vitro.
METHODS
M. tuberculosis (MTB) lose virulence during prolonged culture on artificial media. This loss of virulence is associated with a change in colony morphology. Several studies suggested that trehalose 6,6' dimycolate (TDM or cord factor), contributes to colony morphology.


OBJECTIVE
To investigate the role of TDM in colony morphology of MTB using clinical isolates selected to have colony morphology typical of virulent or attenuated organisms.


METHODS
Use immunohistochemical and physical chemical methods to assess the presence and distribution of TDM in rapidly growing pellicles of MTB.


RESULTS
TDM forms an insoluble crystalline monolayer at the air-water interfaces that is more rigid than that formed by any other biologic amphiphile and is strong enough to support a spreading pellicle of MTB. The surface of young pellicles of the isolate with virulent morphology displayed the regular linear pattern characteristic of monolayers of TDM. TDM was also identified in the open spaces of pellicles of MTB by immunohistochemistry. MTB with morphology of attenuated organisms had neither of these properties.


CONCLUSIONS
These data suggest that the characteristic morphology of colonies of virulent MTB is due to TDM released from the surface of the organisms.
Hunter
Robert Lee
RL
Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, MSB 2.136, 6431 Fannin, Houston, TX 77030, USA. Robert.L.Hunter@UTH.TMC.EDU
Venkataprasad
Nandagopal
N
Olsen
Margaret R
MR
D000818:Animals; D003311:Cord Factors / Q000378:metabolism / Q000502:physiology*; D004195:Disease Models, Animal; D009169:Mycobacterium tuberculosis / Q000254:growth & development* / Q000378:metabolism / Q000472:pathogenicity; D011817:Rabbits; D014774:Virulence
D003311:Cord Factors