Frederic Bertels

January 12, 2022

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Environmental trade-offs of phage infection

We have observed that the efficiency of phage infection is strongly dependent on the environment. Phages that are efficient at infecting bacteria in liquid are usually very inefficient at infecting bacteria growing on solid media. These two types of phages have very different phenotypes. Phages adapted to solid media form large plaques (bacteria free areas on a bacterial lawn) and phages adapted to liquid media form very small plaques. Phages can also very quickly switch from one phenotype to the other by acquiring only a single mutation. During a random mutagenesis screen, we observed that phage adapted to liquid media (forming small plaques) will rapidly yield phage better adapted to solid media (forming large plaques). The ease at which phages switch phenotypes by simple mutations is astounding and leaves a number of questions unanswered. For example, will it become more difficult to switch between environments after multiple switches between phenotypes/genotypes? Will mutations accumulate in a certain part(s) of the genome and what role does genome architecture play for adaptation? Are we going to see evidence for modular genome architecture in phages as has been observed for bacterial genomes? The prospective student will investigate this phenomenon by performing evolution experiments and measure the change in the fitness landscapes between liquid and solid environment.


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