Biochemical and genetic characterization of mechanisms used by soil bacteria to enhance plant growth

植物根部周围有丰富的微生物生命。这些微生物中的一些自然地定居在种子和根上，并刺激根的发育。这对植物是有利的，因为它增加了对水分和土壤养分的吸收，并有助于在土壤中建立幼苗。这些微生物有潜力应用于农业土壤，以提高作物产量。我的研究计划的长期目标是了解有益的土壤细菌如何促进植物生长。许多细菌产生植物激素吲哚乙酸，我们已经确定这对一些细菌刺激根的生长很重要。然而，吲哚乙酸也是由土壤细菌产生的，这些细菌会导致植物中的肿瘤和其他损害。细菌产生吲哚乙酸量的不同可能解释了它们对寄主植物产生不同影响的原因，因此我们将确定控制细菌吲哚乙酸产生的环境和分子因素。利用分子鉴定技术，我们发现了有益的土壤细菌假单胞菌。GR12-2与植物病原菌中的丁香假单胞菌亲缘关系最近。有益的细菌可能具有植物生长刺激所需的基因，而相关病原菌中没有这些基因，因此我们建议对假单胞菌的基因组进行测序。GR12-2，并将该序列与已知的密切相关病原体的基因组序列进行比较。对这些细菌基因组的比较将揭示植物生长促进的新机制，并将为植物生长促进细菌的进化提供洞察力。

The area around the roots of plants is rich with microbial life. Some of these microbes naturally colonize seeds and roots, and stimulate root development. This is beneficial for the plants as it increases absorption of water and soil nutrients, and helps to establish young seedlings in soil. These microbes have the potential to be applied to agricultural soil to increase crop yields. The long-term goal of my research program is to understand how beneficial soil bacteria enhance plant growth. Many bacteria produce the plant hormone indoleacetic acid and we have established that this is important for root growth stimulation by some bacteria. However, indoleacetic acid is also produced by soil bacteria that induce tumors and other lesions in plants. Differences in the amount of indoleacetic acid produced by the bacteria may explain their different effects on host plants, and therefore we will determine the environmental and molecular factors that control bacterial indoleacetic acid production. Using molecular identification techniques, we have found that the beneficial soil bacterium Pseudomonas sp. GR12-2 is most closely related to the Pseudomonas syringae group of plant pathogens. The beneficial bacterium likely has genes required for plant growth stimulation that are not present in the related pathogens and therefore we propose to sequence the genome of Pseudomonas sp. GR12-2 and compare the sequence to the known genome sequences of the closely related pathogens. Comparison of the genomes among these bacteria will reveal novel mechanisms of plant growth-promotion and will provide insight into the evolution of plant growth-promoting bacteria.