BIOTECHNOLOGY
FASTER DIE
GROW
SOONER B
How growth rates infl uence the fi tness of bacteria
acteria are survival artists: when they get nutrition, they multiply rapidly, albeit they can also survive periods of hunger. But when they
grow too quickly, their ability to survive is hampered, as studies by a research team at the Technical University of Munich (TUM) on E. coli bacteria show. T e results could help increase the eff ectiveness of antibiotics. “T e fi tness of bacteria is more complex than expected,” explains Ulrich Gerland, professor for the theory of complex biosystems at the TUM. T e physicist has been studying the survival strategies of E. coli bacteria for several years. T e unicellular organisms, which go by the Latin name Escherichia coli and
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support digestion in the large intestine of mammals, are a popular model organism. T ey facilitate investigations into the way living beings can adapt to changing environmental conditions.
SURVIVING HARD TIMES “We have known for some time that biological fi tness depends on two things: the growth rate when food is available and the ability to survive periods of nutrient defi ciency,” explains the scientist. “What was not clear is how these two factors are related.” For the fi rst time, Gerland and his
team have now systematically investigated the extent to which fast or slow growth infl uences the survivability of E. coli
bacteria: “It turns out that changes in growth conditions have a direct impact on death rates. T ese follow a simple law: T e best-nourished and fastest-growing bacteria are the fi rst to die when deprived of food.”
FAT BACTERIA – POOR FITNESS So, a good diet is bad for the fi tness of bacteria. But why? To fi nd an answer to this question, the TUM researchers carried out a number of experiments. First, cultures of E. coli bacteria were provided nutrient solutions with diff erent compositions. In the second step, the unicellular organisms were put on a zero diet. T roughout the entire period, the scientists examined whether and how quickly the cells multiplied, and how long they survived.
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