The Claim
Mycobacterium tuberculosis requires exogenous vitamin B12 from the host to achieve full virulence, as evidenced by significantly reduced bacterial loads in the lungs and spleen and improved survival in B12-deficient mice, whereas Mycobacterium canettii, which synthesizes vitamin B12 endogenously, does not exhibit this dependency.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
Mycobacterium tuberculosis depends on vitamin B12 obtained from the host to cause severe infection, and without it, bacterial numbers decrease and survival improves in mice. Mycobacterium canettii, which produces its own vitamin B12, does not require host vitamin B12 to cause infection.
See the scientific wording
Mycobacterium tuberculosis requires exogenous vitamin B12 from the host to achieve full virulence, as demonstrated by significantly reduced bacterial loads in the lungs and spleen and improved survival in B12-deficient mice, while the ancestral strain M. canettii, which synthesizes its own B12, shows no such dependency.
Mycobacterium tuberculosis cannot make its own vitamin B12 and must take it from the host. Once inside the bacterium, B12 activates a key enzyme that makes methionine, an essential building block for proteins. Without enough B12 from the host, this enzyme does not work, methionine production drops, and the bacteria cannot grow or spread. A genetic switch in the bacterium shuts down an alternative way to make methionine when B12 is present, making the bacteria completely dependent on the host's supply. This dependency does not exist in a related bacterium that can make its own B12.
What the research says
1 studyStudy: Dependency on host vitamin B12 has shaped Mycobacterium tuberculosis Complex evolution
The tuberculosis bacteria need to steal vitamin B12 from the host to cause serious illness—when the host doesn’t have enough B12, the bacteria get weaker. But a related bacteria that makes its own B12 stays just as strong no matter what.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.