Bacteria can survive starvation in zombie mode

February 21, 2019, University of Amsterdam
Credit: CC0 Public Domain

Bacteria that are exposed to a hostile environment, for example with antibiotics or very few nutrients, can sometimes survive by 'going to sleep." Biologists from the University of Amsterdam (UvA) have discovered an unknown, alternative survival strategy: a kind of zombie mode, in which the bacteria do not sleep, but slow down extremely. Their discovery has been published in the journal Nature Communications.

Bacteria appear to be simple, single-celled organisms. Yet they surprise scientists time and again with all the tricks they are capable of. For example, many bacteria can form so-called endospores under the influence of stress. The dire circumstances drive the bacteria to encapsulate themselves in a special sturdy coat, within which they can safely 'sleep' until more favourable conditions arise. In that dormant state, the bacteria no longer need nutrients and become resistant to damaging influences of, for example, cold, UV light or antibiotics. A good thing for the bacteria, but less beneficial for us: thanks to this trick, bacterial infections can suddenly flare up again after they were seemingly successfully treated with antibiotics.

Starving the bacteria

An international team of biologists, led by Professor Leendert Hamoen of the UvA's Swammerdam Institute for Life Sciences, has now discovered an alternative survival strategy for bacteria that are exposed to extreme conditions. They worked with Bacillus subtilis, a non-pathogenic bacterium that occurs in the soil and which scientists often use as a model organism. The biologists chose a variant of the bacterium that can no longer form endospores due to a mutation. Subsequently, they simply starved the bacteria. Some of the bacteria were found to survive this for a long time, even though they could not retreat to their usual dormant state. Staying active, due to the lack of nutrients, was also not an option. So, how did they survive?

The bacteria were found to take refuge in a third, as yet unknown state. You could call it a kind of zombie state. The zombie bacteria are not really active, nor do they sleep; all types of processes slow down to an extremely low level. "We saw clear differences between the active state, the dormant state and this state," says Hamoen. "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 did not 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."

New light on antibiotics

The researchers themselves, of course, do not call this state a zombie mode. They have named the previously unknown survival strategy oligotrophic growth. This term translates into 'nutrient-poor growth."

Hamoen says, "The big question now is: do bacteria other than Bacillus know this trick too? If so, this fundamentally changes our outlook on bacteria. Apparently, they do not always 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 favourable 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 can escape antibiotics. '

Explore further: How infectious bacteria hibernate through treatment

More information: Declan A. Gray et al. Extreme slow growth as alternative strategy to survive deep starvation in bacteria, Nature Communications (2019). DOI: 10.1038/s41467-019-08719-8

Related Stories

How infectious bacteria hibernate through treatment

September 12, 2018

Disease-causing bacteria can develop resistance to antibiotics which are then no longer effective in treating infection, yet they also have another tactic to avoid being killed off by antibiotic treatment. Some cells of the ...

Double the stress slows down evolution

December 6, 2018

Like other organisms, bacteria constantly have to fight to survive in hostile living conditions. Together with colleagues in Finland, researchers at the Max Planck Institute for Evolutionary Biology in Plön have discovered ...

How persistent bacteria are able to avoid antibiotics

December 29, 2013

The mechanism by which some bacteria are able to survive antibacterial treatment has been revealed for the first time by Hebrew University of Jerusalem researchers.  Their work could pave the way for new ways to control ...

Recommended for you

A decade on, smartphone-like software finally heads to space

March 20, 2019

Once a traditional satellite is launched into space, its physical hardware and computer software stay mostly immutable for the rest of its existence as it orbits the Earth, even as the technology it serves on the ground continues ...

Tiny 'water bears' can teach us about survival

March 20, 2019

Earth's ultimate survivors can weather extreme heat, cold, radiation and even the vacuum of space. Now the U.S. military hopes these tiny critters called tardigrades can teach us about true toughness.

Researchers find hidden proteins in bacteria

March 20, 2019

Scientists at the University of Illinois at Chicago have developed a way to identify the beginning of every gene—known as a translation start site or a start codon—in bacterial cell DNA with a single experiment and, through ...

Turn off a light, save a life, says new study

March 20, 2019

We all know that turning off lights and buying energy-efficient appliances affects our financial bottom line. Now, according to a new study by University of Wisconsin-Madison researchers, we know that saving energy also saves ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Jeffhans1
5 / 5 (1) Feb 21, 2019
It almost sounds as if they need to reclassify the existing states to label the in between one as a sleeping state. The spore state should be labeled something other than sleep.
torbjorn_b_g_larsson
not rated yet Feb 22, 2019
It almost sounds as if they need to reclassify the existing states to label the in between one as a sleeping state.


They did classify it, but sleep is something different from starvation mode. These kinds of modes are both interesting research (c.f. how hard it is to know if sediment trapped bacteria are dying or inactive "waiting for better times") and understandable tropic modes (c.f. fast division under normal and likely competitive conditions vs slow division under starvation).

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.