Evolutionary bacteria ‘invest’ their meagre resources

For the first time the complex interplay between bacterial investment strategies and their outcomes has been recreated and analysed, by an international team of researchers.

The breakthrough was achieved by using synthetic biology to create identical bacteria but with fixed investment strategies, some investing in growth, some in stress resistance and others in both to various degrees.

The researchers said this was the cleanest system yet that precisely defined a relationship between traded objects in a living ‘market’ and permitted the testing of strategies in many different environments.

“Since the 1960s, theories have been available on how decision-making by organisms is related to their survival on one hand or to rapid growth on the other. Both are not possible simultaneously because resources are not sufficient for both,” one researcher said.

“Bacteria, like humans, have limited resources and are constantly faced with decisions on how to invest in their future. Bacteria are hugely successful and have managed to colonise every part of the planet.”

The researchers developed a mathematical model to predict the best way for bacteria to invest resources in a trade-off between growth and stress resistance. It had been believed that the decision-making involved trade-offs that gave biological investors different niches to exploit.

With the engineered organisms it was possible to subject them to a range of different environments with different stresses and growth conditions and, for the first time, the exact nature of bacterial trade-offs could be determined.

The researchers modelled how, like humans investing in cash, bacteria trade in costly proteins to reduce their stress levels or to increase consumption and so grow faster. Evolution is the decision-making process with different choices encoded in the genes.

Each bacterium makes an investment decision; the bad investors fall by the wayside, the good ones survive.

Dr Ivana Gudelj, co-author from Exeter University in Britain, said combining engineered bacteria with mathematical models allowed the researchers to show that similar investment opportunities can require different investment strategies.

“These strategies are constrained by the subtleties in trade-offs that are usually invisible or ignored in real markets. The study is a classic demonstration of Darwinian economics and survival of the fittest,” Gudelj said.

The researchers say the information the model provides about trade-offs and their subtleties will certainly be relevant to researchers in economics, finance and business.

Results of the research were published in the journal Ecology Letters.