When toxins preserve populations

April 17, 2018, Ludwig Maximilian University of Munich
When toxins preserve populations
Credit: Jürgen Fälchle / fotolia.com

Some soil bacteria can alter their environment in such a way as to endanger their own survival – unless, that is, toxins do not impede their growth beforehand.

All living organisms have an impact on their environment. These modifications can have a positive effect on the growth of species that cause them and may also be of benefit to others. However, organisms may also alter their habitats in ways that are not only deleterious to their own survival, but may even lead to their extinction. This phenomenon is known as ecological suicide. In a new study, Ludwig Maximilian University biophysicist Jonas Denk, together with Christoph Ratzke and Professor Jeff Gore of the Massachusetts Institute of Technology (MIT, Boston), have explored the underlying dynamics of the process. Their findings appear in the journal Nature Ecology & Evolution.

The three researchers analyzed the of cultures of the soil bacterium Paenibacillus sp. When grown in weakly buffered medium with glucose as the major carbon source, this species secretes metabolic products that progressively acidify the medium and strongly reduce the local pH. When the pH value reaches approx. 4 the cells begin to die and, within less than 24 h, no viable cells are left. The more food is available, the quicker the population succumbs. However, disaster can be avoided if the buffering strength (which helps to maintain pH) of the medium is enhanced – which proves that the build-up of 'acid waste' is responsible for cell death.

"Each bacterium needs food to survive and reproduce, but the cumulative effects of byproducts of their metabolism ultimately cause the collective self-destruction of the population," says Denk. This in turn leads to the paradoxical effect that other toxic substances, such as alcohols, salts or antibiotics, can promote the survival of a population by inhibiting the growth and replication of its individual members." When populations of Paenibacillus are grown in a medium with a moderate buffering capacity survival becomes dependent on cell density, which gives rise to complex oscillatory dynamics. This emphasizes that besides interactions between different species, which have been thoroughly investigated in the past, interactions between a single species and its environment can be essential to understand the complex dynamics of a .

Since many micro-organisms have the potential to alter their environment in detrimental ways, Denk and colleagues assume that the phenomenon has an important function in microbial ecology and evolution. Out of 21 , the researchers could indeed observe ecological suicide in five of them. "Soil bacteria in nature are part of complex biological communities," Denk points out. "An induced change in pH, for instance, may improve the survival in the short term if it enhances the community's overall ability to cope with a sudden alteration in environmental conditions."

Explore further: Forming patches boosts bacterial life

More information: Christoph Ratzke et al. Ecological suicide in microbes, Nature Ecology & Evolution (2018). DOI: 10.1038/s41559-018-0535-1

Related Stories

Forming patches boosts bacterial life

March 24, 2016

Natural systems such as grasslands form clusters, or patches, that bolster resilience under stress. Experiments show this same behavior can be modeled in bacteria with several important implications for creating survivable ...

Explaining rare plant species

March 7, 2018

Rare plant species suffer more from disease than common species. The fact that rare species are more susceptible to attack by micro-organisms living in the soil, such as fungi and bacteria, may in fact be one of the reasons ...

Capturing the balance of nature

March 2, 2018

In a study spanning 12 years, researchers from Kyoto University and Ryukoku University have developed a method to calculate the fluctuating stability of a natural ecological community in Maizuru Bay.Their findings, published ...

Improving the biodiversity of green roofs

March 1, 2017

Using living organisms such as bacteria or fungi, as an alternative to chemical fertilisers, can improve the soil biodiversity of green roofs, according to new research from the University of Portsmouth.

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

EPA adviser is promoting harmful ideas, scientists say

March 22, 2019

The Trump administration's reliance on industry-funded environmental specialists is again coming under fire, this time by researchers who say that Louis Anthony "Tony" Cox Jr., who leads a key Environmental Protection Agency ...


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.