Cost of Living

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Science  15 Jul 2011:
Vol. 333, Issue 6040, pp. 269
DOI: 10.1126/science.333.6040.269-b

For microorganisms in the open ocean, where oligotrophic waters are limited in essential nutrients such as nitrogen, there is a delicate balance between growth and survival. Adapting to maximize the efficiency of biosynthesis may help defray the costs associated with nutrient limitation, but is there also a pressure over time to actually reduce assimilation of such nutrients into biomolecules as a means of minimizing costs? To answer this, Grzymski and Dussaq evaluated several whole-genome sequences and over 20 million protein fragments from databases to look for differences in the use of nitrogen between open-ocean and coastal microbial communities. Indeed, the atomic compositions of amino acids produced by open-ocean microorganisms contain systematically less nitrogen than coastal microbial proteomes to the point that the overall nitrogen requirement is reduced by up to 10% in the open ocean; however, as nitrogen use is minimized, the average mass of amino acids actually increases. Because the effect is pronounced in highly expressed proteins, there must be a fitness trade-off between increased biosynthetic costs of making larger amino acids and minimizing the use of nitrogen. The results show that nutrients are not only important in the life cycle of extant microorganisms, but that their limitation exerts a strong selective pressure on microorganisms over time.

ISME J. 10.1038/ismej.2011.72 (2011).

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