Bacteria can exchange genetic material with each other, even between species. Rather than being passed down from ancestor to offspring, genetic information is exchanged between organisms living at the same time. By systematically characterizing the fitness effects of this so-called horizontal gene transfer, researchers at the Institute of Biological Physics at the University of Cologne have found that they can predict whether gene transfer accelerates adaptation to certain growing conditions.
The group generated a series of hybrids of the bacterium Bacillus subtilis and related bacterial species by horizontal gene transfer. They then tested the bacteria for their adaptability to environmental factors such as temperature and food supply. They present their findings in the article “Distribution of fitness effects of cross-species transformation reveals potential for rapid adaptive evolution” published in The ISME magazine.
A single bacterial species has only a relatively small genome and reproduces only by copying its own genetic information. The adaptability is therefore limited. However, in community with other species, bacteria can acquire genetic material from their neighbors and incorporate it into their own genome.
But can bacteria actually increase their chances of survival with this new genetic material? Under what conditions does this provide an advantage? Professor dr. Berenike Maier and her team investigated these questions and showed in an evolution experiment that bacteria benefit from the genetic material of other bacteria under certain growing conditions.
The researchers generated a large number of hybrids between the “hay bacillus” Bacillus subtilis and related Bacillus species by horizontal gene transfer and determined their fitness. Fitness describes how quickly a hybrid reproduces compared to the unaltered bacterium, called the parent strain. Rapid growth means that one bacterial species can displace another and thus achieve dominance of its own offspring.
To test their adaptability, the researchers determined the suitability of the hybrids under different environmental conditions, such as elevated temperature or different food sources. “We got a different distribution of fitness effects for each condition. The important question now was whether we could predict from this whether horizontal gene transfer would increase adaptability under a given environmental condition,” said Isabel Rathmann, one of the lead authors of the study.
To test these predictions, the scientists designed a high-throughput evolution experiment in collaboration with Professor Dr. Tobias Bollenbach. The experiment generated populations of different hybrids that competed with each other for nutrients under different growing conditions. The use of a high throughput system made it possible to observe hundreds of such populations over 450 bacterial generations. The first results indicated that the fitness effects distribution can be used to make predictions about the fitness effects of gene transfer.
“We found that under most growing conditions there were some hybrids that were better adapted than the parent strain. This result suggests that a shared gene pool could help bacteria adapt to certain environmental conditions. However, there are also conditions under which gene transfer is not beneficial.” said Mona Förster, another lead author of the study. In the future, the researchers plan to use the method to specifically predict when horizontal gene transfer will accelerate bacterial adaptation.
Strange Bedfellows: The Origin and Evolution of Bacterial Hybrids
Isabel Rathmann et al, Distribution of fitness effects of transformation across species reveals potential for rapid adaptive evolution, The ISME magazine (2022). DOI: 10.1038/s41396-022-01325-5
Quote: Improved Adaptation: Bacteria can benefit from the genetic material of other bacteria (2022, October 13) retrieved October 13, 2022 from https://phys.org/news/2022-10-bacteria-profit-genetic-material.html
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