Defence at almost any price

December 13, 2017

Even bacteria have enemies - in water, for example, single-celled ciliates preferably feed on microbes. The microbes protect themselves against predators by employing a variety of tricks, which the ciliates, in turn, attempt to overcome. There ensues an evolutionary competition for the best attack and defence mechanisms. According to scientists from the Max Planck Institute for Evolutionary Biology in Plön, prey such as bacteria have, in the long run, no choice but to maintain protection mechanisms, even if the effort involved is so high that they can barely produce offspring.

Predator and prey maintain a close relationship to each other: if one evolves, the other must keep pace. Such coevolution and its accompanying selection pressure leads to mutual adaptation of the two species.

In their experiments, Lutz Becks and his fellow Plön-based researchers from Plön, London, and Finland held bacteria and ciliates together for many weeks and traced their evolution. Here, they observed how the microbes protect themselves against the gluttony of the ciliates when, after a few days, the bacterial cells, normally living in isolation, began to grow in larger associations as a slimy "biofilm". This meant they could no longer be foraged as effectively by the ciliates.

Costly defence

As long as the scientists allowed only the bacteria to evolve in their experiments and computer simulations, the bacteria were able to protect themselves well from being eaten - with acceptable effort. However, as soon as the ciliates were also allowed to evolve, protection came at a high cost to the bacteria: they then only produced few offspring. "Protection against predators therefore comes at a high cost, because the better the bacteria are equipped, the worse they reproduce", says Becks.

The bacteria cannot therefore optimize both simultaneously - a typical case of evolutionary trade-off. However, what exact form this trade-off takes depends on whether the predator can adapt to the prey's defence mechanisms. If so, defence becomes increasingly costly to the prey and barely any resources remain for reproduction. In contrast, if the predator cannot adapt, the prey requires fewer resources for defence and can invest more in producing progeny", explains Becks.

Less diversity

In addition, the researchers demonstrated that predator diversity decreases when there is a dynamical trade-off. The ciliates thus develop fewer different types in order to adapt to bacterial associations and biofilms. "This is, of course, beneficial to the prey and could reduce the pressure on the bacteria", says Becks.

The study shows that, surprisingly, more prey diversity does not always mean more predator diversity. Lutz Becks: "What is important are the costs and benefits of traits for prey and predator. As our experiments demonstrate, they can shift depending on whether or not the predator had time to adapt."
Original publication

Weini Huang, Arne Traulsen, Benjamin Werner, Teppo Hiltunen, and Lutz Becks
Dynamical trade-offs arise from antagonistic coevolution and decrease intraspecific diversity.
Nature Communications; 12 December, 2017


Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to