台灣溫泉菌相中遠紅光藍綠菌的相對豐度及其與酸鹼值和溫度之相關性探討

Abstract

大部分藍綠菌僅能生長於可見光 (λ = 400-700 nm) 下，但有部分能吸收遠紅光 (λ = 700-750 nm) 行光合作用，稱之為遠紅光藍綠菌。這些遠紅光藍綠菌過去由多樣的環境中分離，其中多於溫泉環境中發現。然而，傳統方法如色素分析或純化培養難以系統化分析遠紅光藍綠菌的生態分佈。因此，我利用一個16S rRNA基因擴增子定序的方法—FRCI，調查11個臺灣溫泉的微生物群落。此外，透過其中30個溫泉樣本DNA測試專門針對藍綠菌擴增的CYA引子，與16S rRNA基因測序的通用微生物V3V4引子比較，其對藍綠菌分辨能力和效力。 結果顯示，遠紅光藍綠菌在台灣溫泉中分布廣泛，其相對豐度佔整體藍綠菌群落的0%至20%。其中，在龜丹溫泉，遠紅光藍綠菌佔整體藍綠菌群落的55%。此外，遠紅光藍綠菌的相對豐度會隨著溫泉pH值的上升而顯著增加，並且略隨著溫度的降低而減少。測序結果鑑定出11個遠紅光藍綠菌，主要屬於Leptolyngbya和Calothrix屬，此外，本研究也純化出三株先前未知其具有利用遠紅光能力的藍綠菌。我也從其他國家溫泉菌落資料中，發現在許多溫泉中常見的遠紅光藍綠菌Fischerella spp.在台灣僅少量分布，為台灣獨特的溫泉菌相生態提供重要線索。CYA引子在藍綠菌目組成的排序上表現出相似的結果，但在溫泉樣本中發現的多樣性高於V3V4引子。引子偏好的存在需要進一步通過定量的模擬微生物群落進行確認。我們的研究為了解台灣溫泉中獨特的遠紅光藍綠菌群落提供了基礎，並突顯了CYA引子在揭示藍綠菌多樣性方面的重要性。

Some cyanobacteria can harvest far-red light (FRL, wavelength = 700-750 nm) in addition to visible light (wavelength = 400-700 nm) for photosynthesis. These special cyanobacteria (hereafter far-red cyanobacteria) were predominantly isolated from hot springs and characterized by pigment or culture-based methods. However, these methods are limited in studying the distribution and ecological significance of far-red cyanobacteria. In this study, I investigated 11 hot springs in Taiwan using a 16S rRNA gene amplicon sequencing-based method named as Far-Red Cyanobacteria Identification (FRCI). Additionally, 30 hot spring samples were selected and amplified using cyanobacteria-specific CYA primers to compare their resolution and efficacy against the general prokaryotic V3V4 hypervariable regions used for 16S rRNA gene sequencing. My investigation reveals that far-red cyanobacteria were widely distributed in 10 out of 11 hot springs. They comprised 0-55% of the cyanobacterial population. The population size positively correlates with pH value (r = 0.36, p<0.01) and negatively correlates with temperature ( r = -0.28, p<0.05). FRCI identified 11 distinct far-red cyanobacteria ASVs from hot spring samples, primarily belonging to genera Leptolyngbya and Calothrix. Cultivation under FRL revealed three previously unknown strains of cyanobacteria capable of utilizing FRL. These findings expand our understanding of far-red cyanobacterial diversity. Additionally, Fischerella spp. are common far-red cyanobacteria in Japan, China, and India; however, they are the minority in Taiwan hot springs. While CYA primers exhibited a similar ranking of cyanobacterial order composition, they found greater diversity in hot spring samples compared to V3V4 primers. The presence of primer preferences requires further confirmation with a mock community. Our study provides a basis for studying unique far-red cyanobacteria communities in Taiwan hot springs and highlights the importance of CYA primers in uncovering cyanobacterial diversity.