本土光合細菌PS3於水稻生長促進與溫室氣體減排效應之研究

Abstract

水稻栽培為臺灣農業部門中主要的溫室氣體排放源之一。本研究旨在探討本土光合菌Rhodopseudomonas palustris PS3菌株對水稻生長促進以及田間甲烷排放抑制之效果與作用機制。本研究包括三階段試驗，首先進行光合菌PS3菌株與產甲烷菌Methanosarcina barkeri、Methanobacterium spp.的純土壤試驗初步評估PS3菌株在淹水土壤中的甲烷減排潛力，其次於臺灣北部兩處水稻田進行土壤與作物栽培試驗評估其實際應用效果，最後以PS3菌株與產甲烷菌的共培養試驗探討兩微生物間的交互作用情形。研究結果顯示，PS3菌株在純土壤與田間試驗皆可有效降低36-82%的土壤甲烷通量，並於水稻收穫期顯著提升稔實率（34%）與穀粒千粒重（20%）。以穩定碳同位素分析確認PS3菌株並未直接以甲烷作為代謝基質，其抑制甲烷排放效應可能歸因於提升甲烷氧化菌群 (Methylomonas) 活性或是與產甲烷菌競爭醋酸等共同代謝基質所致。在厭氧避光的培養條件下，PS3菌株可能透過氫氣移轉來促進M. barkeri的甲烷生成作用；而在厭氧照光條件下，PS3菌株呈現明顯固碳效益，並大量合成光合色素，抑制高達77%的甲烷累積排放量。本試驗證實PS3菌株在多種環境皆展現穩定的甲烷抑制效果，能有效提升田間稻作產量，同時發現其與土壤中產甲烷菌群間具高度交互作用，為糧食安全與環境永續提供具高度開發潛力之新型栽培技術。

Methane emissions from rice paddies represent a major source of agricultural greenhouse gases. This study examines the potential of Rhodopseudomonas palustris PS3 as a biological agent for mitigating methane emissions while enhancing rice yield. Bulk soil tests, field trials, and co-culture experiments with the methanogen Methanosarcina barkeri were conducted to elucidate PS3’s function. The application of PS3 in bulk soil and rice fields resulted in a 36–82% reduction in CH₄ flux, along with a 34% increase in the filled-spikelet rate and a 20% increase in thousand-grain weight. Stable isotope tracing studies indicated that PS3 does not directly metabolize methane; its ability to reduce emissions is likely attributed to substrate competition or the stimulation of methane-oxidizing bacteria, such as Methylomonas. Under anaerobic-dark conditions, PS3 facilitated methane production through hydrogen transfer to M. barkeri, whereas under anaerobic-illuminated conditions, mimicking surface paddy soils, PS3 activated photoautotrophic metabolism, fixed carbon, and suppressed methane emissions by up to 77%. These findings underscore the dual functionality of PS3 as a methane mitigation agent and yield enhancer, offering a promising microbe-based strategy for sustainable rice cultivation.