在沒有氧的環(huán)境中生活一向被認(rèn)為是細(xì)菌,、病毒和單細(xì)胞生物的“專利”,，但研究人員日前在地中海海底沉積物中發(fā)現(xiàn)3種能在無氧環(huán)境里終生生活的多細(xì)胞動物。
意大利和丹麥研究人員在新一期英國《BMC生物學(xué)》期刊上報(bào)告說,，他們在地中海海底探尋未知生物時(shí)發(fā)現(xiàn),，在無氧和高鹽度的海底沉積物中，生活著3種屬于鎧甲動物門的多細(xì)胞動物,。它們只有1毫米長,，在被發(fā)現(xiàn)時(shí)不僅保持著活躍的新陳代謝，其中一些個體還含有卵細(xì)胞,，顯示出這些動物在無氧環(huán)境中具有繁殖能力,。
研究人員達(dá)諾瓦羅說，以前在海底無氧環(huán)境中只發(fā)現(xiàn)過多細(xì)胞動物的尸體,，一般認(rèn)為它們是沉到海底的,，但這次卻有證據(jù)證明一些多細(xì)胞動物可以一直在海底無氧環(huán)境中生存。這一發(fā)現(xiàn)拓寬了人們對動物生存能力的認(rèn)識,，揭示了自然界中奇特的生物多樣性,。
這項(xiàng)研究還顯示，上述幾種生物具有適應(yīng)無氧環(huán)境的生理機(jī)制,。通常如果動物依靠氧生存,，那么其細(xì)胞內(nèi)會有線粒體，線粒體可以通過氧化為細(xì)胞提供能量,。一些在無氧環(huán)境中生存的單細(xì)胞生物則依靠“氫化酶體”這種細(xì)胞器來提供能量,。而上述新發(fā)現(xiàn)物種的細(xì)胞內(nèi)沒有線粒體，為其提供能量的是與“氫化酶體”類似的細(xì)胞器,。(生物谷Bioon.com)
延伸閱讀
PNAS：細(xì)菌極端環(huán)境受迫生存機(jī)制
Science：南非金礦極端環(huán)境下發(fā)現(xiàn)新細(xì)菌
Science：氧氣起源紛爭再起
生物谷推薦原文出處：
BMC Biology DOI: 10.1186/1741-7007-8-30
The first metazoa living in permanently anoxic conditions
Roberto Danovaro , Antonio Dell'Anno , Antonio Pusceddu , Cristina Gambi , Iben Heiner and Reinhardt Mobjerg Kristensen
Background
Several unicellular organisms (prokaryotes and protozoa) can live under permanently anoxic conditions. Although a few metazoans can survive temporarily in the absence of oxygen, it is believed that multi-cellular organisms cannot spend their entire life cycle without free oxygen. Deep seas include some of the most extreme ecosystems on Earth, such as the deep hypersaline anoxic basins of the Mediterranean Sea. These are permanently anoxic systems inhabited by a huge and partly unexplored microbial biodiversity.
Results
During the last ten years three oceanographic expeditions were conducted to search for the presence of living fauna in the sediments of the deep anoxic hypersaline L'Atalante basin (Mediterranean Sea). We report here that the sediments of the L'Atalante basin are inhabited by three species of the animal phylum Loricifera (Spinoloricus nov. sp., Rugiloricus nov. sp. and Pliciloricus nov. sp.) new to science. Using radioactive tracers, biochemical analyses, quantitative X-ray microanalysis and infrared spectroscopy, scanning and transmission electron microscopy observations on ultra-sections, we provide evidence that these organisms are metabolically active and show specific adaptations to the extreme conditions of the deep basin, such as the lack of mitochondria, and a large number of hydrogenosome-like organelles, associated with endosymbiotic prokaryotes.
Conclusions
This is the first evidence of a metazoan life cycle that is spent entirely in permanently anoxic sediments. Our findings allow us also to conclude that these metazoans live under anoxic conditions through an obligate anaerobic metabolism that is similar to that demonstrated so far only for unicellular eukaryotes. The discovery of these life forms opens new perspectives for the study of metazoan life in habitats lacking molecular oxygen.
