探討沼澤紅假單胞菌PS3菌株促進有機番茄生長與提高土壤微生物燃料電池電能之效果

Abstract

沼澤紅假單胞菌PS3菌株屬於光合細菌，已被視為具有潛力的植物促生根際細菌(PGPR)。過去研究發現無論是在施用化學肥料的土壤或是水耕系統中，施用 PS3皆能有效提升葉菜類的生長。此外，在PS3的基因組中因含有許多與電子傳遞相關的基因，推測它也具有發電的潛力。有鑑於此，本博士論文的研究目的為探討PS3菌株在有機農業與綠色能源中所扮演的角色。

在本論文的第一部分（第二章）探討接種PS3 對於栽種在有機田的番茄其生長與土壤健康的影響。研究結果顯示接種PS3的番茄其果實產量與收穫質量皆高於未接種的對照組。此外土壤養分的可利用性以及與養分循環相關的細菌屬豐度皆伴隨著PS3的接種而增加。為了驗證上述田間試驗結果，採用了兩種不同的番茄品種進行盆栽實驗。研究結果除了再現植株與果實的農藝性狀外，也發現Haliangium屬的微生物豐度在接種PS3的土壤中與田間一樣有明顯增加，推測該屬微生物應與PS3具有協同作用功效。綜上所述，我推測PS3的接種改善了土壤理化性質，同時影響了土壤微生物族群組成，因而促進番茄生長與提升果實品質。

在本論文的第二部分（第三章）則是評估將PS3接種到土壤電池後對於發電的影響以及釐清可促進發電的因子。結果顯示PS3可透過在電極周圍形成生物膜、藉由照光進行二氧化碳固定，並與土壤中的亞鐵離子進行厭氧氧化來提升電極周邊的電子傳遞效率以增強土壤電池的電力。此外，CMOS DC-DC轉換器結合最大功率点追踪（2D-MPPT）技術設計成能量收集系統以能夠穩定且有效率地從土壤內擷取能量。因此，該裝置有望在實際應用上成為高轉換效率、低成本、低耗能的綠能收集系統。 本研究所呈現的沼澤紅假單胞菌在不同層面的應用將可為農業環境與能源問題提供一種有效的永續解決方案。

Rhodopseudomonas palustris strain PS3 is a phototrophic bacterium, which has been considered an elite plant growth-promoting rhizobacterium (PGPR). It could improve the biomass of several leafy crops while it was inoculated in soil treated with chemical fertilizer or in a hydroponic system. This bacterium also contains many putative electron transport-related genes in the genome, suggesting it can act as a potential electricigen to produce electricity. The objective of my Ph.D. study was to elucidate the roles of PS3 in both organic agriculture and green energy. In chapter 2 of this dissertation, I investigated the influence of PS3 on tomato growth and soil health in an organic field. The findings proved that PS3 inoculation did improve the yield of tomato fruit and the harvesting quality. Soil nutrient availability and the abundance of bacterial genera related to nutrient cycling were both increased by PS3 inoculation. The field result was further verified by pot evaluation with two tomato cultivars, and the genus Haliangium was notably higher in the PS3 treatments, suggesting that this genus may have synergistic interactions with PS3. Accordingly, I assume that the improved soil physicochemical and microbiota caused by PS3 inoculation results in beneficial effects on growth, fruit yield, and quality of tomatoes. In chapter 3, I evaluated the effects of PS3 inoculation on the performance of a soil-based microbial fuel cell (MFC), and clarify the essential factors that contributed to its power generation. PS3 could enhance power generation of the apparatus by elevating the electron transport surrounding electrodes through biofilm formation and interplay between phototrophic fixation of ambient CO2 and anaerobic oxidation of ferrous iron in the soil. The CMOS DC-DC converter with 2D-MPPT was designed as a power harvesting system for the soil-based MFCs to harvest energy in a more efficient and reliable fashion. This apparatus is expected to provide a potentially low-cost and low-energy system with a high power conversion efficiency for practical applications in the future. Taken together, this research provides a sustainable solution to the issues of agricultural environment and energy by the application of the elite plant-associated phototrophic bacterium.