Control of Heterocyst Differentiation in Free-Living and Symbiotic Cyanobacteria

该项目的目的是确定生物化学 控制营养细胞分化的机制 到异型囊（好氧固氮的网站）在念珠藻 spp.米克斯博士假设异形胞分化是 在全球氮调节系统的控制下， 生活状态，这可能会被一个共生的具体取代 当念珠藻与该菌结合时， 花角他建议继续定性， 互补--鉴定和分离调控基因 参与异形胞分化。的具体目标 包括分离具有多效性的其它突变体， 不能以硝酸盐和N2为氮源生长的表型 来源，但能够固定N2的共生。这种突变体将是 通过分析回复突变体的类别（单位点 抑制基因突变）。突变表型将被补充 通过接合转移野生型或“回复突变体”DNA克隆 在大肠大肠杆菌中，或在体外包装在质粒中并转移到 通过电穿孔将念珠藻受体转化。互补片段 将被排序并与已建立的数据库进行比较。他们 也将用于野生型的生理遗传学研究 和念珠藻的突变株，以确定它们在 分化 %%% 这项研究对两个领域有影响。首先，它是一种罕见的 细菌中模式形成的例子，因此提供了 一个用强大的基因技术研究的例子 在细菌系统中可用。此外，蓝藻 是环境的重要组成部分， 作为减少碳和氮的主要生产者的作用。一个 因此，了解这些过程是如何控制的 具有普遍重要性。

The intent of the project is to identify the biochemical mechanisms that control the differentiation of vegetative cells into heterocysts (sites of aerobic nitrogen fixation) in Nostoc spp. Dr. Meeks hypothesizes that heterocyst differentiation is under control of a global nitrogen regulatory system in the free- living state, that may be superseded by a symbiotic specific system when Nostoc is in association with the bryophyte anthoceros. He proposes to continue characterization and complementation - to identify and isolate regulatory genes involved in heterocyst differentiation. The specific objectives include isolation of additional mutants with the pleiotropic phenotype of inability to grow with nitrate and N2 as nitrogen sources, but able to fix N2 in symbiosis. Such mutants will be characterized by analysis of classes of revertant (single site suppressor mutations). The mutant phenotypes will be complemented by conjugational transfer of wild type or "revertant" DNA cloned in E. coli or packaged in vitro in plasmids and transferred into the Nostoc recipient by electroporation. complementing fragments will be sequenced and compared to established data banks. They will also be used in physiological genetic studies with wild type and mutant strains of Nostoc to define their role in differentiation. %%% This study has implications for two areas. First it is a rare example of pattern formation in bacteria and therefore provides an example to study with the powerful genetic techniques available in bacterial system. Additionally, the cyanobacteria are important components of the environment and play a unique role as primary producers of reduced carbon and nitrogen. An understanding of how these processes are controlled is therefore of general importance.