Monthly Archives: January 2016

Phenotypic switching and biological evolution of microbes

Finally! After all these years (sorry Andrew, bad joke) we have finally posted our paper on phenotypic switching and biological evolution of bacteria on arxiv and biorxiv, see here. In short, the paper proposes a mathematical model which shows how switching between phenotypes speeds up biological evolution. Previously, phenotypic switching has been hypothesised to have evolved (1) as a “bet-hedging” strategy, (2) as a “division of labour” strategy to conserve resources. Now we have added a 3rd possibility which may play a particularly important role in the evolution of antibiotic resistance.

The credit for this work goes to Andrew Tadrowski – a very organized and meticulous PhD student with great attention to details. Andrew spent a lot of time making sure that all figures look eye-catching (as much as they can for a mathematical model). One of them – a schematic representation of the model – is displayed below.

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computer-controlled evolution of drug resistance

I have been playing recently with simple, computer-controlled systems for growing bacteria in the presence of antibiotics. The picture shows a “morbidostat” that I have build (see here for the first system of this type). I want to use it to track how bacteria evolve resistance to drugs.

The system consists of a small tube (20ml) holding the bacteria, a magnetic stirrer, three peristaltic pumps, an infrared LED and a phototransistor to measure turbidity of the culture, and a few other things, all inside a transparent incubator set to 37C.

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The plot shows how the population of bacteria (E. coli) responds to the increasing concentration of the drug (ciprofloxacin). The drug is kept at a level that stresses the bacteria and forces them to evolve.

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