Microbial Genome Sequencing: Genome Sequencing of a Nitrogen-Fixing Bacterial Endophyte

20世纪50年代至70年代的绿色革命预示着作物产量的大幅增加，主要是通过使用氮肥。然而，氮肥在经济上和环境上都是昂贵的。氮肥是农业中最高的农业成本之一。大量的化石燃料被用来生产这些化肥，成本不断上升。此外，土壤中的大部分固定氮素从未被植物吸收，而是渗入地下水中，污染了美国许多农村地区的大部分饮用水。为了消除对氮肥的需求，需要发现能够为小麦和玉米等农业中的重要牧草提供固定氮素的细菌。近年来，从生长只需要很少氮素的牧草品系中分离出了几种固氮菌。固氮菌的研究已经有100多年的历史了，它们从大气中捕获氮气，并将其转化为一种可供植物使用的氮气。Triplett实验室分离的其中一种细菌得到了广泛的研究，能够入侵许多植物的内部，而不会引起疾病症状。这种菌株之所以大量进入植物，可能是因为它要么逃避，要么未能诱导出阻止其他细菌进入植物的植物防御机制。事实上，这种肺炎克雷伯氏菌342(Kp342)实际上促进了植物的生长。在小麦(但不是其他牧草)中，Kp342实际上为植物提供了固定的氮素，在没有任何氮肥的情况下种植可以缓解缺氮症状。为了进一步提高该菌株向小麦、玉米、水稻和其他牧草提供氮素的能力，需要更多关于Kp342的S代谢和调控电路的基础知识。了解更多关于这种菌株的最彻底和最有效的方法是通过确定这种生物的整个基因组序列。一旦知道了序列，就会仔细检查，以发现这种有机体中的每一个基因。基因组研究所和佛罗里达大学将对Kp342进行完整的基因组测序。随着Kp342中每个基因的发现，将在培训和推广方面做出重大努力。佛罗里达大学将为本科生和研究生设立暑期研讨会，学生们将在那里学习比较固氮菌、细菌内生菌和克雷伯氏菌菌株的基因组。将进行一项重要的外展工作，以制定一项全国性的基因组科学课程，供对科学和技术感兴趣的美国青年使用。

The green revolution of the 1950s-1970s heralded large increases in crop yields largely through the use of nitrogen fertilizers. However, nitrogen fertilization is expensive economically and environmentally. Nitrogen fertilization is one of the highest on-farm costs in agriculture. A significant amount of fossil fuel is used to produce these fertilizers at an ever-increasing cost. In addition, much of the fixed nitrogen applied to soils is never taken up by the plants and leaches into ground water, contaminating much of the drinking water in many rural areas of the United States. To eliminate the need for nitrogen fertilization, bacteria need to be discovered that can provide fixed nitrogen to important grasses in agriculture such as wheat and corn. In recent years, several nitrogen-fixing bacteria have been isolated from lines of grasses that require very little nitrogen for growth. Nitrogen-fixing bacteria have been studied for over 100 years and they capture N2 from the atmosphere and convert it to a form of nitrogen that can be used by plants.One of the bacteria isolated in the Triplett laboratory has been studied extensively and is capable of invading the interior of many plants without causing disease symptoms. This strain probably enters plants in such high numbers because it either eludes, or fails to induce, plant defense mechanisms that would prevent other bacteria from entering the plant. In fact, this strain, Klebsiella pneumoniae 342 (Kp342), actually enhances plant growth. In wheat (but not other grasses), Kp342 actually provides fixed nitrogen to plants and can relieve N-deficiency symptoms when cultured in the absence of any nitrogen fertilizer. More basic knowledge of Kp342's metabolism and regulatory circuits is needed in order to further improve this strain's ability to provide nitrogen to wheat, corn, rice, and other grasses. The most thorough and effective way to learn more about this strain is through determining the entire genome sequence of this organism. Once the sequence is known, it will be examined carefully to discover every gene in this organism. The Institute for Genomic Research and the University of Florida will perform complete genome sequencing of Kp342. With the discovery of every gene in Kp342 will come a significant effort in training and outreach. A summer workshop will be established for undergraduate and graduate students at the University of Florida where students will learn to compare the genomes of nitrogen fixing bacteria, bacterial endophytes, and Klebsiella strains. A significant outreach effort will be done to develop a national curriculum in genome science that will be available to the youth in America who are interested in science and technology.