此前一直预测气单胞菌是通过L-DOPA途径形成真黑素，因为从多株产黑气单胞菌菌株的培养液中都能检测到特征性中间产物L-DOPA的存在。但我们的近期研究却证实， 经尿黑酸（HGA）途径形成的脓黑素才是高产黑色素的中间气单胞菌WS的主要色素成分。该HGA途径在所有产黑、仅在低温下产黑或完全不产黑，以及致病或非致病的气单胞菌中都普遍存在，且相关基因均表达正常。说明气单胞菌的黑色素合成调控过程及实际生物学效应远比我们预想的复杂。本申请拟以前期工作为基础，对气单胞菌属细菌合成脓黑素的关键调控元件、黑色素与致病性的相关性、以及该菌是否同时产生两种黑色素等问题进行进一步深入研究。研究结果将在理论上进一步扩展对细菌合成黑色素的分子机理及生物学功能的认识，在应用上则可为构建黑色素高产或弱产微生物发酵菌株，开发新的产L-DOPA菌种资源，甚至在拓展对人尿黑酸尿症的认识和治疗措施方面提供新的思路和技术基础。

In previous time, it is generally believed that Aeromonas bacteria should produce eumelanin via L-DOPA pathway, since the characteristic intermediate L-DOPA could be detected from the culture fluids of several melanogenic Aeromonas strains. However, our recent results demonstrated that the pyomelanin produced via Homogentisate acid (HGA) pathway is actually the major pigment constituents in the melanin high-producing strain Aeromonas media WS. Such HGA pathway is ubiquitous and every gene in the pathway is functioning normally among all species in this genus, including those with phenotype of pigmented, pigmented only in low temperature, and non-pigmented, and both pathogenic or non-pathogenic Aeromonas. Therefore, the pigment synthetic regulation process in Aeromonas bacteria and its biological function are much more complex than our current knowledge. Based on our current works, we plan to conduct further research on the key transcriptional regulators relating to the pyomelanin production, the relativity between bacterial melanogenesis and pathogenicity, and whether Aeromonas bacteria could produce two kinds of melanin at the same time. The achieved results may theoretically extend our knowledge on the molecular mechanism of melanin synthesis and its biological function in bacteria, and from the application point of view, may contribute in providing new ideas and technical basis to construct high or low melanin producing microbial fermentation strains, develop new bacterial recourses for L-DOPA production, and even expand our knowledge and potential therapeutic measure on human alkaptonuria.