[B-GM22] 地球惑星科学と微生物生態学の接点

[BGM22-02] 環境中には未知なる脱窒微生物が豊富に存在している

*磯部 一夫¹、Wei Wei¹、妹尾 啓史¹ (1.東京大学大学院農学生命科学研究科)

キーワード：脱窒, 亜硝酸還元酵素遺伝子, nirS, nirK

Denitrification is an important process in the global nitrogen cycle. The genes encoding NirK and NirS (nirK and nirS), which catalyze the reduction of nitrite to nitric oxide, have been used as marker genes to study the ecological behavior of denitrifiers in environments. However, conventional polymerase chain reaction (PCR) primers can only detect a limited range of the phylogenetically diverse nirK and nirS. Thus, we developed new PCR primers covering the diverse nirK and nirS. Clone library and qPCR analysis using the primers showed that nirK and nirS in terrestrial environments are more phylogenetically diverse and 2-6 times more abundant than those revealed with the conventional primers. RNA- and culture-based analyses using a cropland soil also suggested that microorganisms with previously unconsidered nirK or nirS are responsible for denitrification in the soil. PCR techniques still have a greater capacity for the deep analysis of target genes than PCR-independent methods including metagenome analysis, although efforts are needed to minimize the PCR biases. The methodology and the insights obtained here should allow us to achieve a more precise understanding of the ecological behavior of denitrifiers and facilitate more precise estimate of denitrification in environments.