Overexpression of Adenylyl Cyclase Encoded by the Mycobacterium tuberculosis Rv2212 Gene Confers Improved Fitness, Accelerated Recovery from Dormancy and Enhanced Virulence in Miceстатья
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Аннотация:Earlier we demonstrated that the adenylyl cyclase (AC) encoded by the MSMEG_4279
gene plays a key role in the resuscitation and growth of dormant Mycobacterium
smegmatis and that overexpression of this gene leads to an increase in intracellular
cAMP concentration and prevents the transition of M. smegmatis from active growth to
dormancy in an extended stationary phase accompanied by medium acidification. We
surmised that the homologous Rv2212 gene of M. tuberculosis (Mtb), the main cAMP
producer, plays similar physiological roles by supporting, under these conditions, the
active state and reactivation of dormant bacteria. To test this hypothesis, we established
Mtb strain overexpressing Rv2212 and compared its in vitro and in vivo growth
characteristics with a control strain. In vitro, the AC-overexpressing pMindRv2212 strain
demonstrated faster growth in a liquid medium, prolonged capacity to form CFUs and
a significant delay or even prevention of transition toward dormancy. AC-overexpressing
cells exhibited easier recovery from dormancy. In vivo, AC-overexpressing bacteria
demonstrated significantly higher growth rates (virulence) in the lungs and spleens
of infected mice compared to the control strain, and, unlike the latter, killed mice in
the TB-resistant strain before month 8 of infection. Even in the absence of selecting
hygromycin B, all pMindRv2212 CFUs retained the Rv2212 insert during in vivo growth,
strongly suggesting that AC overexpression is beneficial for bacteria. Taken together,
our results indicate that cAMP supports the maintenance of Mtb cells vitality under
unfavorable conditions in vitro and their virulence in vivo.