编辑点评: GRE阅读的方法相信大家已经积累了很多了,本文就为大家提供一些GRE阅读的材料,大家来练一练,把平时学到的东西运用到实际中,也多多积累词汇和句子,提高自己的阅读能力。
每天做一些标准的GRE阅读练习,有助于大家在GRE考试的复习过程中不断地进行练习和总结。希望大家在进行GRE阅读练习时,充分运用平时所积累的知识,这样才能有效果。
Although pathogenic organisms constantly alight on the skin, they find it a very unfavorable environment and, in the absence of injury, have great difficulty colonizing it. This self-sterilizing capacity of the skin results from the tendency of all well-developed ecosystems toward homeostasis, or the maintenance of the status quo.
Species that typically live in soil, water, and elsewhere rarely multiply on the skin. Undamaged skin is also unfavorable to most human pathogens. The skin is too acid and too arid for some species. The constant shedding of the surface skin layers further hinders the establishment of invaders. The most interesting defense mechanism, however, results from the metabolic activities of the resident flora . Unsaturated fatty acids, an important component of the lipids in sebum collected from the skin surface, inhibit the growth of several bacterial and fungal cutaneous pathogens. These acids are a metabolic product of certain gram-positive members of the cutaneous community, which break down the more complex lipids in freshly secreted sebum.
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