Villa Juan A, Ray Erin E, Barney Brett M
Biotechnology Institute, University of Minnesota, St. Paul, MN, USA.
FEMS Microbiol Lett. 2014 Feb;351(1):70-77. doi: 10.1111/1574-6968.12347. Epub 2014 Jan 9.
Microalgae are viewed as a potential future agricultural and biofuel feedstock and also provide an ideal biological means of carbon sequestration based on rapid growth rates and high biomass yields. Any potential improvement using high-yield microalgae to fix carbon will require additional fertilizer inputs to provide the necessary nitrogen required for protein and nucleotide biosynthesis. The free-living diazotroph Azotobacter vinelandii can fix nitrogen under aerobic conditions in the presence of reduced carbon sources such as sucrose or glycerol and is also known to produce a variety of siderophores to scavenge different metals from the environment. In this study, we identified two strains of green algae, Neochloris oleoabundans and Scenedesmus sp. BA032, that are able to utilize the A. vinelandii siderophore azotobactin as a source of nitrogen to support growth. When grown in a co-culture, S. sp. BA032 and N. oleoabundans obtained the nitrogen required for growth through the association with A. vinelandii. These results, indicating a commensalistic relationship, provide a proof of concept for developing a mutualistic or symbiotic relationship between these two species using siderophores as a nitrogen shuttle and might further indicate an additional fate of siderophores in the environment.
微藻被视为未来潜在的农业和生物燃料原料，并且基于其快速生长速率和高生物量产量，还提供了一种理想的碳固存生物学手段。利用高产微藻固定碳的任何潜在改进都将需要额外投入肥料，以提供蛋白质和核苷酸生物合成所需的必要氮源。自由生活的固氮菌维涅兰德固氮菌（Azotobacter vinelandii）在有氧条件下，于存在蔗糖或甘油等还原碳源时能够固定氮，并且还已知会产生多种铁载体以从环境中清除不同金属。在本研究中，我们鉴定出两株绿藻，即多油新绿藻（Neochloris oleoabundans）和栅藻属（Scenedesmus）BA032，它们能够利用维涅兰德固氮菌的铁载体固氮菌素作为氮源来支持生长。当在共培养中生长时，栅藻属BA032和多油新绿藻通过与维涅兰德固氮菌的关联获得生长所需的氮。这些结果表明了一种共生关系，为利用铁载体作为氮穿梭体在这两个物种之间建立互利或共生关系提供了概念验证，并且可能进一步表明了铁载体在环境中的另一种归宿。
