在自然界,，表現型之間的隨機切換（“風險對沖”）是生物在變幻無常的環(huán)境中求生存的常見現象。對暴露于一個與脊椎動物免疫系統(tǒng)等環(huán)境有相似性的波動體系中的“熒光假單孢菌”所做的一項研究,，實時顯示了這種行為何以能夠發(fā)生,。
本期封面所示為一個“熒光假單孢菌”菌種的菌落，這個菌種已形成了在不同菌落類型之間隨機切換的能力,。這種“風險對沖”策略使它們能夠在一個不斷變化,、以對不同菌落有利的人工環(huán)境中存活。“風險對沖”在實驗室中的形成以及其中所涉及突變的識別,，反映了動態(tài)環(huán)境是怎樣推動這種“風險對沖”行為之形成的,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 462, 90-93 (5 November 2009) | doi:10.1038/nature08504
Experimental evolution of bet hedging
Hubertus J. E. Beaumont1,2,3, Jenna Gallie1, Christian Kost1,3, Gayle C. Ferguson1 & Paul B. Rainey1
1 New Zealand Institute for Advanced Study and Allan Wilson Centre for Molecular Ecology & Evolution, Massey University, Private Bag 102904, North Shore Mail Centre, North Shore City 0745, Auckland, New Zealand
2 Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands
3 Present addresses: Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands (H.J.E.B.); Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany (C.K.).
Correspondence to: Hubertus J. E. Beaumont1,2,3 Correspondence and requests for materials should be addressed to H.J.E.B.
Bet hedging—stochastic switching between phenotypic states1, 2, 3—is a canonical example of an evolutionary adaptation that facilitates persistence in the face of fluctuating environmental conditions. Although bet hedging is found in organisms ranging from bacteria to humans4, 5, 6, 7, 8, 9, 10, direct evidence for an adaptive origin of this behaviour is lacking11. Here we report the de novo evolution of bet hedging in experimental bacterial populations. Bacteria were subjected to an environment that continually favoured new phenotypic states. Initially, our regime drove the successive evolution of novel phenotypes by mutation and selection; however, in two (of 12) replicates this trend was broken by the evolution of bet-hedging genotypes that persisted because of rapid stochastic phenotype switching. Genome re-sequencing of one of these switching types revealed nine mutations that distinguished it from the ancestor. The final mutation was both necessary and sufficient for rapid phenotype switching; nonetheless, the evolution of bet hedging was contingent upon earlier mutations that altered the relative fitness effect of the final mutation. These findings capture the adaptive evolution of bet hedging in the simplest of organisms, and suggest that risk-spreading strategies may have been among the earliest evolutionary solutions to life in fluctuating environments.
