生物谷報道：澳大利亞昆士蘭大學的研究人員在地球上一些保存最久的有機材料中發(fā)現(xiàn)了有35億年歷史的一些最古老的微生物遺體,。這個由Miryam Glikson等人領導的研究隊伍首次確定性地證實了這些有機材料的本質(zhì)和來源。這項研究的結果發(fā)表在近期的Precambrain Research雜志上。
Golding博士表示,，之前的研究利用間接的分析方法進行研究,，而這類方法只能揭示出微生物的內(nèi)含物而不能證實它就是微生物,。
該研究組利用了復雜且耗時的電子顯微鏡技術來確定微生物遺體,。他們將觀察分析技術和微生物分析技術結合起來進行鑒定。
研究人員還對化石微生物結構和在海底發(fā)現(xiàn)的距今35億年前的原始微生物進行了比較,。結果發(fā)現(xiàn),，培養(yǎng)的微生物體在瓦解階段的結構和那些古老的微生物遺體存在很多相似之處。
有關誰是地球上最古老的生命形式一直存在爭議,。在過去的10多年里,，研究生命起源的研究人員將這個頭銜給了一群生活在80到90度高溫的地熱口和溫泉的細菌——超耐溫菌。但是2002年的一項研究則挑戰(zhàn)了這個認識,，該研究發(fā)現(xiàn)這個頭銜應該給一種存活條件更溫和的細菌,。
越來越多的證據(jù)表明，耐熱細菌并非第一個出現(xiàn)在地球的生命形式,。研究發(fā)現(xiàn)位于進化數(shù)基部的物種實際上一種耐寒細菌類群——浮霉狀菌目（planctomycetales）,。這種細菌具有一些奇怪的特征，如染色體外包被一個單層或雙層膜,。
法國巴黎的研究人員從現(xiàn)存的浮霉狀菌中提取核糖體RNA進行測序,，并利用一種計算機程序來分析測序數(shù)據(jù)。因為所有細胞生物都含有核糖體RNA,，所以核糖體RNA被視為研究生命進化的一個強有力的依據(jù),。研究人員將研究的重點放在了核糖體RNA分子突變速度很慢的部分，由于這個部分在進化中保守性較高,，因此能夠揭示出生物體之間的古老關系,。
事實上，在20多年前就有研究人員提出浮霉狀菌才是最古老最早的細菌,，但后來被超耐熱菌所取代,。
英文原文：
Source: University of Queensland
Date: August 7, 2007
More on: Microbes and More, Origin of Life, Organic, Microbiology, Fossils, Soil Types
Microbial Remains Of Some Of The Oldest Forms Of Life Discovered
Science Daily — University of Queensland researchers have identified microbial remains in some of the oldest preserved organic matter on Earth, confirmed to be 3.5 billion years-old.
The UQ team, led by School of Physical Sciences scientists Dr Miryam Glikson and Associate Professor Sue Golding as well as Associate Professor Lindsay Sly from the School of Molecular & Microbial Sciences, are the first to conclusively confirm the nature and source of the organic material.
"What we have found is the first visual confirmation of primitive microbial communities in what is considered to be the best preserved ancient organic matter on our planet," Dr Glikson, the instigator of the research, said.
Dr Golding, Director UQ's Stable Isotope Laboratory in the Division of Earth Sciences, said previous studies used indirect analytical methods that were only able to suggest microbial involvement, not confirm it.
TEM micrograph of carbonaceous matter concentrate after demineralisation of rock. Single 'cell' bodies showing micro porosity and central cavity following dissolution of mineral matter (which filled the cavities in the whole rock; the mineral was silica). (Credit: Image courtesy of University of Queensland)
"We used difficult and time-consuming electron microscope techniques to conclusively confirm the microbial remains," Dr Golding said.
"The integration of observational and micro-analytical techniques is unique to our approach."
The core drilling samples from Western Australia's Pilbara region were collected by PhD student Lawrie Duck who said it was an amazing experience to "hold in your hands rocks that contain remains of some of the earliest forms of life on Earth."
"The Pilbara region is such a good research site as it has ancient forms of the white smokers active at plate margins today and black sulfidic smokers found in sea floor vent systems in tectonically active sites," he said.
"These are the places where scientists believe life on Earth might have had its origins."
Dr Glikson said the UQ team had then taken the study further by comparing the fossil microbial structures to primitive microbes found today in seafloor environments similar to those existing 3.5 billion years ago.
"The microbiologists on the team, led by Dr Sly, cultured currently existing primitive microbes under simulated conditions to those of the ancient forms of life," Dr Glikson said.
"A remarkable resemblance was found between the structures of the cultured microbial entities at their stage of disintegration and those of the ancient microbial remains."The other members of the UQ research team were Robyn Webb, from the Centre for Microscopy and Microanalysis, a specialist in transmission electron microscopical techniques; Justice Baiano, from the School of Molecular & Microbial Sciences, who developed special facilities to culture primitive microbes derived from seafloor mineral-laden hot springs active at plate margins today; and Kim Baublys, from the Stable Isotope Laboratory, who undertook analysis of products from the culture experiments.
A comparison with organic matter from rocks of similar age in South Africa also yielded microbial remains identical to those from the Pilbara, further confirming the UQ work. This was achieved with the collaboration of Dr Axel Hofmann from the University of Kwazulu, South Africa and Dr Robert Bolhar formerly of the University of Canterbury, New Zealand.
Aspects of the research have been published in Precambrian Research.
The research was funded by an Australian Research Council Discovery grant awarded to Dr Glikson and Dr Sly.
