| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Some amoebae(变形虫) do what many people do. Before they travel, they pack a lunch. In results of a study reported today in the journal Nature, evolutionary1 biologists Joan Strassmann and David Queller2 of Rice University show that long-studied social amoebae Dictyostellum discoideum (commonly known as slime molds粘液菌) increase their odds3 of survival through a rudimentary(基本的,初步的) form of agriculture. Research by lead author Debra Brock, a graduate student at Rice, found that some amoebae sequester4(使隔离,使隐退) their food--particular strains of bacteria--for later use. "We now know that primitively5 social slime molds have genetic6 variation in their ability to farm beneficial bacteria as a food source," says George Gilchrist, program director in the National Science Foundation's Division of Environmental Biology, which funded the research. "But the catch is that with the benefits of a portable food source, comes the cost of harboring harmful bacteria." After these "farmer" amoebae aggregate7 into a slug(鼻涕虫) , they migrate in search of nourishment--and form a fruiting body, or a stalk of dead amoebae topped by a sorus(芽胞囊群) , a structure containing fertile spores8. Then they release the bacteria-containing spores to the environment as feedstock for continued growth. The findings run counter to the presumption9(推测) that all "Dicty" eat everything in sight before they enter the social spore-forming stage. Non-farmer amoebae do eat everything, but farmers were found to leave food uneaten, and their slugs don't travel as far. Perhaps because they don't have to. The advantages of going hungry now to ensure a good food supply later are clear, as farmers are able to thrive in environments in which non-farmers find little food. The researchers found that about a third of wild-collected Dicty are farmers. Instead of consuming all the bacteria they encounter, these amoebae eat less and incorporate bacteria into their migratory10 systems. Brock showed that carrying bacteria is a genetic trait by eliminating all living bacteria from four farmers and four non-farmers--the control group--by treating them with antibiotics11. All amoebae were grown on dead bacteria; tests confirmed that they were free of live bacteria. When the eight clones were then fed live bacteria, the farmers all regained12 their abilities to seed bacteria colonies, while the non-farmers did not. Dicty(时髦的,高级的) farmers are always farmers; non-farmers never learn. Rice graduate student Tracy Douglas co-authored the paper with Brock, Queller and Strassmann. She confirmed that farmers and non-farmers belong to the same species and do not form a distinct evolved group. Still, mysteries remain. The researchers want to know what genetic differences separate farmers from non-farmers. They also wonder why farmer clones don't migrate as far as their counterparts. It might be a consequence of bacterial13 interference, they say, or an evolved response, since farmers carry the seeds of their own food supply and don't need to go as far. Also, some seemingly useless or even harmful bacteria are not consumed as food, but may serve an as-yet-undetermined function, Brock says. That has implications for treating disease as it may, for instance, provide clues to the way tuberculosis14(肺结核) bacteria invade cells, says Strassmann, infecting the host while resisting attempts to break them down. The results demonstrate the importance of working in natural environments with wild organisms whose complex ties to their living environment have not been broken. 点击收听单词发音
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
上一篇:废气发电研究取得突破 下一篇:科学家揭示艾滋病毒外壳完整结构 |
- 发表评论
-
- 最新评论 进入详细评论页>>