- Researchers have identified a previously unknown survival state in bacteria
- In this ‘zombie’ state, they’re not asleep but have slowed down to extreme levels
- Experts say it could help to explain how some bacteria survive antibiotics
Some bacteria appear to go into a zombie-like state in order to survive extreme conditions.
A new study has identified a previously unknown survival strategy in the single-celled organisms that could help to explain why infections re-emerge after treatment.
In this mode, the bacteria are not asleep, but instead demonstrate processes that have been slowed down to the extreme while still remaining somewhat active.
Some bacteria appear to go into a zombie-like state in order to survive extreme conditions. The non-pathogenic bacterium, Bacillus subtilis, which demonstrated the unusual tactic.
In a study published to Nature Communications, researchers investigated the survival strategies of the non-pathogenic bacterium, Bacillus subtilis.
The bacteria were starved for long periods of time, and the team observed their response.
While bacteria are known to form what are known as endospores under stressful conditions, which allow them to ‘sleep’ within a protective coating, the specimens in the study represented a variant that could not do this as the result of a mutation.
Even without the ability to become dormant, however, the researchers found that some were still able to survive.
This was thanks to a third, previously unknown state the team is now calling oligotrophic growth.
‘We saw clear differences between the active state, the dormant state and this state,’ said Professor Leendert Hamoen of the University of Amsterdam’s Swammerdam Institute for Life Sciences.
‘Normally, Bacillus is rod-shaped, but the starved bacteria shrank until they were almost spherical. All kinds of processes that are normally active in the bacterium were altered.
‘But they didn’t stop completely, as happens when the bacterium retreats to a spore in a dormant state.
‘The bacteria even continued to divide. Only not once every forty minutes, but once every four days; more than a hundred times slower than usual.’
WHAT IS ANTIBIOTIC RESISTANCE?
Antibiotics have been doled out unnecessarily by GPs and hospital staff for decades, fueling once harmless bacteria to become ‘superbugs.’
The World Health Organization has previously warned if nothing is done the world was headed for a ‘post-antibiotic’ era.
Bacteria can become drug resistant when people take incorrect doses of antibiotics, or they are given out unnecessarily.Figures estimate that superbugs will kill ten million people each year by 2050, with patients succumbing to once harmless bugs.
Around 700,000 people already die yearly due to drug-resistant infections including tuberculosis (TB), HIV and malaria across the world.
Concerns have repeatedly been raised that medicine will be taken back to the ‘dark ages’ if antibiotics are rendered ineffective in the coming years.
In addition to existing drugs becoming less effective, there have only been one or two new antibiotics developed in the last 30 years.
This zombie-like state translates to mean ‘nutrient-poor growth,’ and has never been seen before.
But, the new findings raise questions about how prevalent it might be.
Spore-forming allows bacteria to resist extreme environments including cold, UV light, and antibiotics in a dormant state.
Similarly, the so-called zombie mode appears to help them survive even when starved of nutrients.
‘The big question is: do bacteria other than Bacillus know this trick too?’ Hamoen asks.
‘If so, this fundamentally changes our outlook on bacteria. Apparently, they do not always have to form spores to survive,’ the researcher says.
‘Apparently, they do not have to form spores to survive. Forming endospores requires a lot of energy, and the bacteria are not always able to “wake up” from this condition.
‘It is much easier for them to switch to and from this oligotrophic growth state. Once conditions improve, they can easily form new colonies.
‘Hence this state is much more favorable for them. If more bacteria are found to be able to switch to this state, it will throw a whole new light on, among other things, how bacteria can escape antibiotics.’