圖為生長(zhǎng)在智利阿塔卡馬沙漠地下兩米疏水基底的微生物
近日,，美國(guó)物理學(xué)家組織網(wǎng)報(bào)道,，西班牙天體生物學(xué)中心和智利北部天主教大學(xué)的研究人員，通過(guò)一種類似于探測(cè)火星土壤底層生命跡象的儀器，在智利阿塔卡馬沙漠地下兩米的疏水基底發(fā)現(xiàn)一個(gè)“微生物的綠洲”。這個(gè)有關(guān)“生命能夠在地球上最干旱的沙漠下繁衍”的研究刊登在最新一期的《天體生物學(xué)》Astrobiology雜志上。
該團(tuán)隊(duì)的科學(xué)家在這個(gè)沙漠下的“綠洲”發(fā)現(xiàn)了棲息的細(xì)菌和古生菌（原始微生物）,，于是將其命名為“微生物的綠洲”。西班牙天體生物學(xué)中心研究員維克托解釋說(shuō),，微生物得以棲息是因?yàn)檫@里蘊(yùn)含可吸附水分的巖鹽和其他高吸濕化合物,，如硬石膏和高氯酸鹽。此外,，基底下的微生物易潮解,，這意味著它們可以吸收有限空氣中的水分，凝結(jié)于鹽晶體表面,，從而形成了幾微米厚的薄膜,。這些物種與其他類似的在多鹽環(huán)境下生長(zhǎng)的種類沒(méi)有什么不同，只是奇特的是,，它們竟被發(fā)現(xiàn)在沒(méi)有任何氧氣或陽(yáng)光的地下2米至3米深處,。
在這項(xiàng)科學(xué)研究中，該小組采用的是自行開(kāi)發(fā)被稱為SOLID的探測(cè)儀探測(cè)生命跡象,，以備未來(lái)用于火星探測(cè)任務(wù),。該儀器的核心是一種叫作LD Chip的生物芯片，包括450種抗體,，以確定生物材料,，如糖,、DNA和蛋白質(zhì)。其可將采集的樣本自動(dòng)進(jìn)行培養(yǎng)和處理,，用影像來(lái)反映觀察結(jié)果,，如果其中有亮點(diǎn)即表明其中存在某些化合物和微生物,。
研究人員通過(guò)這種技術(shù)證實(shí)在沙漠底下有古生菌和細(xì)菌的存在,。他們把沙漠深度達(dá)5米處所采集的樣品帶進(jìn)實(shí)驗(yàn)室，不僅用電子顯微鏡觀察拍照,，還為這些微生物補(bǔ)給水分,。
維克托強(qiáng)調(diào)，如果火星上有類似的微生物或其上有相似的環(huán)境,，也可以采用在阿塔卡馬沙漠的這種儀器來(lái)探測(cè),。在這個(gè)紅色星球上已發(fā)現(xiàn)含鹽水的沉積物，因此其底土有可能存在多鹽的環(huán)境,。而這種高濃度的鹽具有雙重作用,，既可吸收晶體的水，又可降低冰點(diǎn),，使其能夠在零下幾攝氏度到20攝氏度形成薄鹽膜,。（生物谷Bioon.com）
doi:10.1089/ast.2011.0654
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A Microbial Oasis in the Hypersaline Atacama Subsurface Discovered by a Life Detector Chip: Implications for the Search for Life on Mars
Victor Parro,1 Graciela de Diego-Castilla,1 Mercedes Moreno-Paz,1 Yolanda Blanco,1 Patricia Cruz-Gil,1 José A. Rodríguez-Manfredi,2 David Fernández-Remolar,3 Felipe Gómez,3 Manuel J. Gómez,1 Luis A. Rivas,1 Cecilia Demergasso,4,5 Alex Echeverría,4 Viviana N. Urtuvia,4 Marta Ruiz-Bermejo,1 Miriam García-Villadangos,1 Marina Postigo,1 Mónica Sánchez-Román,3 Guillermo Chong-Díaz,5,6 and Javier Gómez-Elvira2
The Atacama Desert has long been considered a good Mars analogue for testing instrumentation for planetary exploration, but very few data (if any) have been reported about the geomicrobiology of its salt-rich subsurface. We performed a Mars analogue drilling campaign next to the Salar Grande (Atacama, Chile) in July 2009, and several cores and powder samples from up to 5 m deep were analyzed in situ with LDChip300 (a Life Detector Chip containing 300 antibodies). Here, we show the discovery of a hypersaline subsurface microbial habitat associated with halite-, nitrate-, and perchlorate-containing salts at 2 m deep. LDChip300 detected bacteria, archaea, and other biological material (DNA, exopolysaccharides, some peptides) from the analysis of less than 0.5 g of ground core sample. The results were supported by oligonucleotide microarray hybridization in the field and finally confirmed by molecular phylogenetic analysis and direct visualization of microbial cells bound to halite crystals in the laboratory. Geochemical analyses revealed a habitat with abundant hygroscopic salts like halite (up to 260 g kg−1) and perchlorate (41.13 μg g−1 maximum), which allow deliquescence events at low relative humidity. Thin liquid water films would permit microbes to proliferate by using detected organic acids like acetate (19.14 μg g−1) or formate (76.06 μg g−1) as electron donors, and sulfate (15875 μg g−1), nitrate (13490 μg g−1), or perchlorate as acceptors. Our results correlate with the discovery of similar hygroscopic salts and possible deliquescence processes on Mars, and open new search strategies for subsurface martian biota. The performance demonstrated by our LDChip300 validates this technology for planetary exploration, particularly for the search for life on Mars.
