Evolution of a Genetic Island of Catabolic Diversity in Bacteria

细菌分解代谢多样性遗传岛的进化

• 批准号: 9603980
• 负责人: L.Nicholas Ornston
• 金额: $ 30.9万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-03-15 至 2001-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9603980&HistoricalAwards=false
• 关键词: Evolution; Genetic; Island; Catabolic; Diversity

Ornston 9603980 We shall expand knowledge of an Acinetobacter chromosomal segment that allows growth of the bacteria with many different chemicals from the environment. Presently sequenced and open to genetic investigation is the pca-qui-pob cluster containing genes associated with catabolism of quinate (qui), shikimate (qui) and 4-hydroxybenzoate (pob) through protocatechuate (pca). Downstream from pobA are genes provisionally designated caf and required for catabolism of chemically analogous plant products (caffeate, coumarate and ferulate) through metabolic reactions that give rise to protocatechuate. After this DNA has been cloned and sequenced, it will be subjected to genetic analysis by a simple procedure that allows selection of strains in which caf genes are defective. The results will expand knowledge of both the evolutionary source and the biochemical mechanisms of enzymes that catabolize caffeate, coumarate and ferulate. The enzymes are likely to share ancestry with enzymes associated with the (-oxidation of fatty acids. Thus the combination of evolutionary and genetic investigations is designed to elucidate how genes for a classical metabolic sequence have been adapted to novel metabolic challenges. Variations upon the metabolic theme of ( oxidation are represented in catIJF and pcaIJF, nearly identical chromosomal segments that exchange sequence information by gene conversion. The potential contribution of this intracellular horizontal sequence transfer to concerted divergence of catIJF and pcaIJF in divergent Acinetobacter cell lines will be compared with the rates of divergence of caf genes with analogous biochemical functions. Knowledge emerging from the foregoing studies will define further a chromosomal island of catabolic diversity, the pca-qui-pob-caf gene cluster containing genetic information allowing growth of Acinetobacter with a wide range of compounds in the environment. The nutrients support the growth of many but not all representatives of the genus Acinetobacte r. We shall characterize genetic variants of the pca-qui-pob-caf gene cluster from different Acinetobacter cell lines. Particular attention will be directed to strains exhibiting phenotypes indicating that portions of the cluster are absent. We shall determine the extent to which the missing phenotypic properties reflect the absence of DNA required for their maintenance. This evidence will indicate if the known phenotypic variations are the consequence of abrupt genetic discontinuities that may help to distinguish members of different genomospecies within the complex genus Acinetobacter. If genetic variations in the pca-qui-pob-caf cluster are concordant with biological separation of Acinetobacter genomospecies by other criteria, it may be possible to infer how evolution of different cell lines within the genus was influenced by different sets of nutritional opportunities within the environment. This project will expand knowledge of evolutionary mechanisms that led to the extraordinary ability of bacteria to remove chemicals from the environment. Application of such knowledge may improve the biological cleanup of environmental chemicals and also may assist in development of processes for bacterial conversion of natural resources to chemicals with improved value for society.

Ornston 9603980我们将扩展不动杆菌染色体片段的知识，该片段允许细菌与环境中的许多不同化学物质一起生长。目前测序和开放的遗传研究是pca-qui-pob簇，包含通过原儿茶酸（pca）与奎尼酸（qui），莽草酸（qui）和4-羟基苯甲酸（pob）的catabetrin相关的基因。pobA的下游是暂时指定为caf的基因，并且是通过产生原儿茶酸的代谢反应来催化化学类似的植物产物（咖啡酸盐、香豆酸盐和阿魏酸盐）所必需的。在该DNA被克隆和测序后，将通过一个简单的程序对其进行遗传分析，该程序允许选择其中caf基因有缺陷的菌株。这些结果将扩大对咖啡酸、香豆酸和阿魏酸分解代谢酶的进化来源和生化机制的认识。这些酶很可能与脂肪酸的β-氧化相关的酶有共同的祖先。因此，进化和遗传研究的结合旨在阐明经典代谢序列的基因如何适应新的代谢挑战。 氧化代谢主题的变化在catIJF和pcaIJF中有代表性，几乎 通过基因转换交换序列信息的相同染色体片段。这种细胞内水平序列转移的潜在贡献catIJF和pcaIJF在分歧不动杆菌细胞系的一致分歧将与具有类似生化功能的caf基因的分歧率进行比较。 从上述研究中获得的知识将进一步定义分解代谢多样性的染色体岛，pca-qui-pob-caf基因簇包含允许不动杆菌在环境中与广泛的化合物一起生长的遗传信息。营养物质支持许多但不是所有不动杆菌属的代表的生长。我们将表征来自不同不动杆菌细胞系的pca-qui-pob-caf基因簇的遗传变体。将特别关注表现出表明簇的部分不存在的表型的菌株。我们将确定缺失的表型特性在多大程度上反映了维持它们所需的DNA的缺失。这一证据将表明，如果已知的表型变异是突然的遗传不连续性的结果，可能有助于区分复杂的不动杆菌属内的不同基因组种的成员。如果pca-qui-pob-caf簇中的遗传变异与通过其他标准对不动杆菌基因种的生物分离一致，则可能推断该属内不同细胞系的进化如何受到环境中不同营养机会的影响。 该项目将扩大进化机制的知识，导致细菌从环境中去除化学物质的非凡能力。 这些知识的应用可以改善环境化学品的生物净化，也可以帮助开发将自然资源细菌转化为对社会具有更高价值的化学品的工艺。