Grow faster, die sooner

How growth rates influence the fitness of bacteria - Bacteria 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. The results could help increase the effectiveness of antibiotics. "The fitness of bacteria is more complex than expected," explains Ulrich Gerland, professor for the theory of complex biosystems at the Technical University of Munich. The physicist has been studying the survival strategies of E. coli bacteria for several years. The unicellular organisms, which go by the Latin name Escherichia coli and support digestion in the large intestine of mammals, are a popular model organism. They facilitate investigations into the way living beings can adapt to changing environmental conditions. "We have known for some time that biological fitness depends on two things: the growth rate when food is available and the ability to survive periods of nutrient deficiency," explains the scientist. "What was not clear is how these two factors are related." For the first time, Gerland and his team have now systematically investigated the extent to which fast or slow growth influences the survivability of E. coli bacteria: "It turns out that changes in growth conditions have a direct impact on death rates. These follow a simple law: The best-nourished and fastest-growing bacteria are the first to die when deprived of food." So, a good diet is bad for the fitness of bacteria. But why?