TB bacteria feed on carbon monoxide

Carbon monoxide is a silent killer that can cause death in minutes — but while it is lethal for humans, Monash University microbiologists have found that some pathogens utilise this deadly gas as an energy source when other nutrients are not available. Their work has been published in The ISME Journal.

Associate Professor Chris Greening and his team focused their research on mycobacteria, a bacterial group that causes killer diseases such as tuberculosis (TB), leprosy and Buruli ulcer. During infection, these microbes are in a hostile environment with very few nutrients to go around, meaning that anything they can do to get extra energy can be hugely advantageous.

“When microbial cells are starved of their preferred energy sources, one way they subsist is by scavenging gases such as carbon monoxide,” said Monash PhD student Paul Cordero, co-lead author on the study.

“They break down this gas into its fundamental components, which provide the cells just enough energy to persist.”

The researchers showed that an enzyme called carbon monoxide dehydrogenase is what allows mycobacteria to obtain energy from this gas. While the energy gained is not enough to allow for growth, the researchers found that carbon monoxide consumption allowed mycobacteria to survive for longer periods of time.

Their findings suggest that Mycobacterium tuberculosis, which has been present in humans since ancient times, might be able to survive inside hosts by using carbon monoxide. As noted by PhD candidate Katie Bayly, co-first author on the study, “It has been known for years that Mycobacterium tuberculosis can use carbon monoxide, but nobody knew why.

“Based on these findings, we predict that it uses this gas to its advantage to persist inside human lungs.

“Our immune cells actually make small amounts of carbon monoxide, which the bacterium may be able to use as an energy supply while dormant.”

Dormancy allows Mycobacterium tuberculosis to stay alive inside patients for years. This dormant infection usually has no symptoms but can advance into full-blown TB — for example, when people become immunocompromised.

This new discovery on the survival mechanism of mycobacteria could thus pave the way for new strategies to better fight communicable diseases such as tuberculosis.

Image credit: ©stock.adobe.com/au/Kateryna_Kon

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