Science: Teeming life in ocean deeps

 作者:班倪拾     |      日期:2019-03-01 01:10:02
By ROSIE MESTEL in LOS ANGELES Primitive microorganisms discovered in the world’s deep oceans may be the most abundant organisms on Earth, says an American microbial ecologist. Jed Fuhrman of the University of Southern California in Los Angeles first described these new members of the kingdom archaea in 1992. In general, this group of microorganisms look much like bacteria, but diverged from them early in the evolution of life. Fuhrman’s team has now sampled more locations and report that this new subset of Archaea may be widespread, especially in the deep sea. Fuhrman and his colleagues first detected the organisms in samples of seawater taken more than 500 kilometres off the coast of California. They extracted DNA from the mix of microorganisms in the water, then analysed a particular gene – called 16S rDNA – which varies from species to species, and found that a totally new form was present in the samples. This suggested that the researchers had stumbled upon a new group of microorganisms. Fuhrman is now trying to culture them in his laboratory. About the same time, microbiologist Ed De Long of the University of California at Santa Barbara reported finding the same group of microorganisms in coastal seawater off Woods Hole, Massachusetts and Santa Barbara. Since their initial discovery, Fuhrman and De Long have sampled other waters at different times and a range of depths to learn more about the distribution of the microorganisms. At last week’s meeting of the American Society for Microbiology in Las Vegas, Nevada, Fuhrman reported finding the microorganisms in deep waters in both the Atlantic and Pacific Oceans, and on coral reefs around Singapore. De Long reported that the microorganisms are present even in the Antarctic Ocean. As a kingdom, the archaea are known for the inhospitable habitats they pick to live in – hot springs, deep ocean vents, and salt flats. For instance, the new group’s closest known relatives are a group called pyrodictium, which thrive in temperatures of 105 °C. The new group, by contrast, generally prefers frigid conditions, of 5 °C or thereabouts. Fuhrman’s DNA analysis – which he says is only a rough guide to numbers – suggests that the microorganisms may account for one-third of all those present in the deep oceans. ‘The deep sea is a huge habitat – it covers three-quarters of the Earth,’ says Fuhrman. ‘So, based on our very limited sampling so far,