Bacterial adaptation through loss of function

The metabolic capabilities and regulatory networks of bacteria have been optimized by evolution in response to selective pressures present in each species' native ecological niche. In a new environment, however, the same bacteria may grow poorly due to regulatory constraints or biochemical defi...

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Bibliographic Details
Published in:	PLoS genetics 2013-07, Vol.9 (7), p.e1003617
Main Authors:	Hottes, Alison K, Freddolino, Peter L, Khare, Anupama, Donnell, Zachary N, Liu, Julia C, Tavazoie, Saeed
Format:	Article
Language:	eng
Subjects:	Acquisitions & mergers Adaptation (Physiology) Adaptation, Physiological - genetics Antibiotics Bacteria Bacteria - genetics Bacterial genetics Biology Directed Molecular Evolution DNA Transposable Elements - genetics Environment Experiments Food Genes Genomes Metabolism Mutation Niche (Ecology) Physical fitness Selection, Genetic
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Summary:	The metabolic capabilities and regulatory networks of bacteria have been optimized by evolution in response to selective pressures present in each species' native ecological niche. In a new environment, however, the same bacteria may grow poorly due to regulatory constraints or biochemical deficiencies. Adaptation to such conditions can proceed through the acquisition of new cellular functionality due to gain of function mutations or via modulation of cellular networks. Using selection experiments on transposon-mutagenized libraries of bacteria, we illustrate that even under conditions of extreme nutrient limitation, substantial adaptation can be achieved solely through loss of function mutations, which rewire the metabolism of the cell without gain of enzymatic or sensory function. A systematic analysis of similar experiments under more than 100 conditions reveals that adaptive loss of function mutations exist for many environmental challenges. Drawing on a wealth of examples from published articles, we detail the range of mechanisms through which loss-of-function mutations can generate such beneficial regulatory changes, without the need for rare, specific mutations to fine-tune enzymatic activities or network connections. The high rate at which loss-of-function mutations occur suggests that null mutations play an underappreciated role in the early stages of adaption of bacterial populations to new environments.
ISSN:	1553-7404 1553-7390 1553-7404