圖片說明：細(xì)菌敢死隊(duì)幫助它們的同伴存活下去,。
（圖片來源：MICHAEL ABBEY / SCIENCE PHOTO LIBRARY）
瑞士和加拿大科學(xué)家近日研究發(fā)現(xiàn),，有些細(xì)菌在入侵腸道的過程中會(huì)進(jìn)行自我破壞性協(xié)作（即自殺）,，猶如敢死隊(duì)一樣,，它們這樣做可以幫助其它的“兄弟”們占領(lǐng)腸道要塞,，進(jìn)行更具破壞性的感染,。相關(guān)論文發(fā)表在8月21日的《自然》（Nature）雜志上。
領(lǐng)導(dǎo)此次研究的是瑞士綜合生物學(xué)研究所的Martin Ackermann,。研究發(fā)現(xiàn),，細(xì)菌S. typhimurium會(huì)表達(dá)分泌系統(tǒng)毒性因子（TTSS-1），引起腸道炎癥,。這樣它就消滅了其它的競(jìng)爭(zhēng)對(duì)手,，同時(shí)也殺死了附近大部分的S. typhimurium。不過剩下的S. typhimurium因而能夠進(jìn)一步感染腸道,。
研究小組成員Wolf-Dietrich Hardt說：“我們認(rèn)為這是一個(gè)非常奇怪的現(xiàn)象,。腸道里的細(xì)菌在遺傳上是同樣的，但是它們其中一些準(zhǔn)備好為群體利益犧牲自己,。”
只有一部分的細(xì)菌表達(dá)TTSS-1,，這就使得敢死隊(duì)細(xì)菌的基因能夠在群體存在下去。如果每個(gè)細(xì)菌都表達(dá)TTSS-1,，那么所有的細(xì)菌都會(huì)自殺,，對(duì)群體無益。
研究人員總結(jié)說,，如果群體利益足夠大,，自我破壞性協(xié)作就能產(chǎn)生。更關(guān)鍵的是,，協(xié)作的個(gè)體必須能夠比不協(xié)作的個(gè)體更經(jīng)常地從其它協(xié)作行為中獲利,。
此次研究結(jié)果有力地支持了長(zhǎng)期存在的利他和合作進(jìn)化理論，同時(shí)也有助于設(shè)計(jì)更多的對(duì)付致病菌的策略,。Hardt說：“基于我們的研究,，如果只有一小部分的細(xì)菌表達(dá)毒性因子的話，那么通常的針對(duì)毒性因子的疫苗策略可能并不是最好的,。”（生物谷Bioon.com）
生物谷推薦原始出處：
Nature,，454, 987-990，Martin Ackermann,，Michael Doebeli
Self-destructive cooperation mediated by phenotypic noise
Martin Ackermann1, Bärbel Stecher2, Nikki E. Freed1, Pascal Songhet2, Wolf-Dietrich Hardt2 & Michael Doebeli3
Institute of Integrative Biology, ETH Zurich, 8092 Zürich, Switzerland
Institute of Microbiology, ETH Zurich, 8093 Zürich, Switzerland
Department of Zoology and Department of Mathematics, University of British Columbia, Vancouver BC V6T 1Z4, Canada
In many biological examples of cooperation, individuals that cooperate cannot benefit from the resulting public good. This is especially clear in cases of self-destructive cooperation, where individuals die when helping others. If self-destructive cooperation is genetically encoded, these genes can only be maintained if they are expressed by just a fraction of their carriers, whereas the other fraction benefits from the public good. One mechanism that can mediate this differentiation into two phenotypically different sub-populations is phenotypic noise1, 2. Here we show that noisy expression of self-destructive cooperation can evolve if individuals that have a higher probability for self-destruction have, on average, access to larger public goods. This situation, which we refer to as assortment, can arise if the environment is spatially structured. These results provide a new perspective on the significance of phenotypic noise in bacterial pathogenesis: it might promote the formation of cooperative sub-populations that die while preparing the ground for a successful infection. We show experimentally that this model captures essential features of Salmonella typhimurium pathogenesis. We conclude that noisily expressed self-destructive cooperative actions can evolve under conditions of assortment, that self-destructive cooperation is a plausible biological function of phenotypic noise, and that self-destructive cooperation mediated by phenotypic noise could be important in bacterial pathogenesis.
