細(xì)菌孢子是地球上抵抗性的有機(jī)體，而且其攜帶有額外的蛋白質(zhì)外層，這是先前的研究所沒(méi)有發(fā)現(xiàn)的。該研究結(jié)果發(fā)布在一期的Current Biology雜志上，這項(xiàng)發(fā)現(xiàn)有助于深入理解肉毒桿菌，破傷風(fēng)桿菌和炭疽桿菌等細(xì)菌的生存方式。

這項(xiàng)研究是由紐約大學(xué)基因組和系統(tǒng)生物學(xué)研究中心，洛約拉大學(xué)醫(yī)學(xué)中心和普林斯頓大學(xué)分子生物學(xué)系的科學(xué)家共同完成的。

科研人員以非致病性細(xì)菌Bacillus subtilis的孢子作為研究對(duì)象，Bacillus subtilis是土壤中一種常見(jiàn)的細(xì)菌。盡管它是非致病性的，但Bacillus subtilis存在很多與含有孢子的病原體相同的結(jié)構(gòu)特征。他們對(duì)組成孢子保護(hù)層的蛋白進(jìn)行檢測(cè)，先前的研究主要關(guān)注孢子保護(hù)層的組成成分，其大約由70種不同的蛋白組成，但幾乎沒(méi)有研究關(guān)注這些蛋白在形成孢子保護(hù)層過(guò)程中的互作機(jī)制。

為了研究蛋白之間的互作，研究人員檢測(cè)了正常孢子和突變孢子外層的形成。在突變的孢子中，他們對(duì)所選擇的外層蛋白進(jìn)行基因移除處理，這就使得研究人員能夠了解，對(duì)于孢子的外衣來(lái)說(shuō)，哪些蛋白是必需的，而哪些蛋白又是無(wú)關(guān)的。

為了在活體細(xì)胞中觀察蛋白質(zhì)的行為，研究人員將編碼孢子外衣蛋白的基因綁定到標(biāo)記物上，標(biāo)記物是一種綠色熒光蛋白。這一步驟能夠檢測(cè)到蛋白形成孢子保護(hù)外衣的過(guò)程。通過(guò)熒光顯微鏡實(shí)驗(yàn)和高分辨率成像分析技術(shù)的結(jié)合使用，研究人員建立了一個(gè)孢子外層的圖譜。實(shí)驗(yàn)結(jié)果表明在孢子外層上存在著新的外層結(jié)構(gòu)。使用電子顯微鏡，研究人員能夠證實(shí)這個(gè)新外層的存在。

研究人員將這個(gè)孢子的外層命名為"孢子殼"（spore crust），但還沒(méi)有*確認(rèn)，這個(gè)外層是所有孢子結(jié)構(gòu)細(xì)菌的共同特征，比如肉毒桿菌，破傷風(fēng)桿菌，炭疽桿菌等

這項(xiàng)研究是由美國(guó)國(guó)家綜合醫(yī)學(xué)研究所支持的。

推薦原文出處：

Current  Biology doi:10.1016/j.cub.2010.03.060

A Distance-Weighted Interaction Map Reveals a Previously Uncharacterized Layer of the Bacillus subtilis Spore Coat
Peter T. McKenney1, Adam Driks2, Haig A. Eskandarian1, 4, Paul Grabowski1, 5, Jonathan Guberman3, Katherine H. Wang1, 6, Zemer Gitai3 and Patrick Eichenberger1, ,

1 Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY 10003, USA
2 Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, IL 60153, USA
3 Department of Molecular Biology, Princeton University, Princeton, NJ 08540, USA

Bacillus subtilis spores are encased in a protein assembly called the spore coat that is made up of at least 70 different proteins. Conventional electron microscopy shows the coat to be organized into two distinct layers. Because the coat is about as wide as the theoretical limit of light microscopy, quantitatively measuring the localization of individual coat proteins within the coat is challenging. We used fusions of coat proteins to green fluorescent protein to map genetic dependencies for coat assembly and to define three independent subnetworks of coat proteins. To complement the genetic data, we measured coat protein localization at subpixel resolution and integrated these two data sets to produce a distance-weighted genetic interaction map. Using these data, we predict that the coat comprises at least four spatially distinct layers, including a previously uncharacterized glycoprotein outermost layer that we name the spore crust. We found that crust assembly depends on proteins we predicted to localize to the crust. The crust may be conserved in all Bacillus spores and may play critical functions in the environment.