Cyclic Glucan Biosynthesis and Phospholipid Metabolism of Bradyrhizobium

慢生根瘤菌的环葡聚糖生物合成和磷脂代谢

• 批准号: 8803247
• 负责人: Karen Miller
• 金额: $ 21万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-07-15 至 1991-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8803247&HistoricalAwards=false
• 关键词: Cyclic; Glucan; Biosynthesis; Phospholipid; Metabolism

The long-term objective of the proposed research is to gain a further understanding of rhizobial bacteroid differentiation, a process essential for the development of effective nitrogen-fixing nodules on the roots of leguminous plants. Several lines of evidence have indicated that the cell- envelope composition of the Rhizobiaceae provides an essential function in this important microbial-plant symbiosis. The experimental plan will focus upon the characterization of the phospholipid and cyclic glucan oligosaccharide content of the cell-envelope of species of Bradyrhizobium. In addition, the phospholipid metabolism of the bradyrhizobia will be examined as well as the enzymic activities associated with the biosynthesis of the cyclic glucans of these bacteria. Experiments are based upon preliminary studies by the applicant that have indicated that the phospholipid metabolism of species of the Rhizobiaceae is intimately linked to the biosynthesis of the cyclic glucans of these bacteria. An important aspect of the proposed studies will be the examination of bradyrhizobial phospholipid and cyclic glucan content before, during, and after the induction of nitrogen-fixation in free-living microaerobic cultures.%%% The availability of water and a source of combined or fixed nitrogen represent the two most limiting factors in agricultural productivity. Because crop plants are not able to fix nitrogen, it must be provided in fixed form. This may be accomplished through the use of industrially synthesized nitrogen fertilizer, however, this synthetic process represents a very costly one in terms of the expenditure of fossil fuels. An alternative mechanism for acquiring fixed nitrogen has evolved in which certain plants are able to participate in a complex symbiotic relationship with nitrogen-fixing bacteria. The symbiotic relationship between leguminous plants and members of the family Rhizobiaceae represents not only an important source of globally fixed nitrogen, but also the most well-studied example of such symbiosis. The overall goal of this project is to gain further understanding of rhizobial bacteroid differentiation - a process essential for the successful development of nitrogen- fixing nodules on the roots of leguminous plants.***//

该研究的长期目标是进一步了解根瘤菌类菌分化，这是豆科植物根部有效固氮根瘤发育所必需的过程。 一些证据表明根瘤菌科的细胞包膜组成在这种重要的微生物-植物共生中提供了重要的功能。 该实验计划将重点关注慢生根瘤菌属物种细胞包膜的磷脂和环葡聚糖寡糖含量的表征。 此外，还将检查缓生根瘤菌的磷脂代谢以及与这些细菌的环葡聚糖生物合成相关的酶活性。 实验基于申请人的初步研究，该研究表明根瘤菌科物种的磷脂代谢与这些细菌的环葡聚糖的生物合成密切相关。 拟议研究的一个重要方面将是在自由生活的微需氧培养物中诱导固氮之前、期间和之后检查缓生根瘤菌磷脂和环葡聚糖含量。%%% 水的可用性和组合或水源固定氮是农业生产力的两个最限制因素。 由于农作物不能固氮，因此必须以固定形式提供。 这可以通过使用工业合成氮肥来实现，然而，就化石燃料的支出而言，这种合成过程是非常昂贵的。 一种获取固定氮的替代机制已经出现，其中某些植物能够参与与固氮细菌的复杂共生关系。 豆科植物与根瘤菌科成员之间的共生关系不仅代表了全球固定氮的重要来源，而且也是这种共生关系最深入研究的例子。 该项目的总体目标是进一步了解根瘤菌类菌分化——这是豆科植物根部成功发育固氮根的关键过程。***//