Host of environmental interactions of members of the rhizobiales order of alphaproteobacteria

在过去的十年中，细菌基因组完整序列的测定从根本上改变了微生物研究。现在，许多努力是针对新发现的基因和转录调控途径的功能的鉴定。具有良好特性的苜蓿中华根瘤菌是这类研究的主要模型系统。它形成苜蓿根瘤，其中大气中的氮转化为氨，对植物有益，减轻了对氮肥的需求。S.草蛉细胞利用各种碳基质生长;这种杂食性可能有助于在土壤中和植物根部附近生存的能力。在被称为短链淀粉酶/还原酶（SDR）的78个成员的蛋白质家族中发现了对分解代谢能力有贡献的几个候选者。在以前的工作中，我们已经在S.苜蓿基因组，并通过随后的表型分析确定，其中几个事实上是需要利用特定的碳源，并与紫花苜蓿的有效共生。我们现在将重点关注每个SDR编码基因周围基因的突变分析，试图了解所涉及的机制。我们还在研究有效共生所需的关键转录调控系统，该系统在与植物，动物和人类形成共生或致病相互作用的相关细菌中是保守的。我们已经开发了一种新的和简单的DNA结合陷阱检测，以确定潜在的转录因子结合位点。我们将使用这种方法来确定这个转录调控系统的目标，然后继续研究目标基因的功能，并评估它们在共生中的参与。最后，我们正在开发另一种细菌，人苍白杆菌，作为宿主病原体相互作用的模型系统。虽然这种微生物与人类病原体布鲁氏菌（Brucella）关系非常密切，并且本身是一种机会性人类病原体，但它似乎也能够在土壤和根际中具有更多样的生活方式。使用比较基因组分析，其次是实验分析，我们将调查共享的机制。

In the past decade, the determination of the complete sequences of bacterial genomes has radically altered microbiological research. Much effort is now directed towards the identification of the functions of newly discovered genes and transcriptional regulation pathways. The well-characterized bacterium Sinorhizobium meliloti is a leading model system for this type of research. It forms alfalfa root nodules in which atmospheric nitrogen is converted to ammonia for the benefit of the plant, relieving the need for nitrogen fertilizers. S. meliloti cells use a variety of carbon substrates for growth; this omnivory probably contributes to ability to survive in the soil and near the plant roots. Several candidates for contribution to the catabolic capacity are found within the 78-member family of proteins called short chain dehydrogenases / reductases (SDR). In previous work, we have made mutations in all SDR-encoding genes in the S. meliloti genome, and through subsequent phenotypic analysis determined that several of them are in fact required for utilization of specific carbon sources, and for effective symbiosis with alfalfa. We will now focus on mutational analysis of genes surrounding each of the SDR-encoding genes, in an attempt to understand the mechanisms involved. We are also studying a key transcriptional regulatory system that is required for effective symbiosis, and is conserved in related bacteria that form symbiotic or pathogenic interactions with plants, animals and humans. We have developed a novel and simple DNA binding trap assay to identify potential transcriptional factor binding sites. We will use this assay to identify the targets for this transcriptional regulatory system, and then go on to study the functions of the target genes and evaluate their involvement in symbiosis. Finally, we are developing another bacterium, Ochrobactrum anthropi, as a model system for host pathogen interaction. Although this organism is quite closely related to the human pathogen Brucella, and is itself an opportunistic human pathogen, it also appears to be capable of a more versatile lifestyle in the soil and rhizosphere. Using comparative genomic analysis, followed by experimental analysis, we will investigate shared mechanisms.