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Báo cáo y học: "nteresting things come in small packages"

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Wertheim cung cấp cho các bạn kiến thức về ngành y đề tài: Interesting things come in small packages. | DeLong Genome Biology 2010 11 118 http genomebiology.eom 2010 11 5 118 w Genome Biology RESEARCH HIGHLIGHT L__ Interesting things eome in small packages Edward F DeLong Abstract Population metagenomics reveals the reduced metabolic capacities of a marine nitrogen-fixing cyanobacterium that lacks many of the signature features of typical cyanobacteria. In life it s said that few things are certain except death and taxes. Similarly in biology while there are exceptions to many rules there do seem to be a few certainties that have stood the test of time. One of these is the general organization and structure of the photosynthetic apparatus in chlorophyll-containing green plants and cyanobacteria in which the photosynthetic electrontransport chain consists of two photosystems one of which generates oxygen. However a study by Jonathan Zehr and colleagues recently published in Nature Tripp et al. 1 presents an unprecedented exception to the general concept of what constitutes the essential core genome of free-living chlorophyll-containing cyanobacteria. The story begins with molecular surveys of nitrogenfixing microorganisms in ocean surface waters. Biological nitrogen fixation is carried out only by certain species of bacteria for example cyanobacteria and rhizobia and archaea for example some methanogens and represents a crucial component of the global nitrogen cycle converting atmospheric nitrogen into biologically available nutrients. Nitrogen fixation is of special interest to oceanographers and biogeochemical modelers as it helps feed vast nutrient-poor regions of the open ocean. Microscopic surveys of ocean plankton had initially indicated that only a few species - in particular large filamentous cyanobacteria such as Trichodesmium - were responsible for the bulk of open-ocean nitrogen fixation 2 . Later however molecular surveys for nitrogenase genes which encode the enzymes responsible for nitrogen fixation suggested that microorganisms other .