食葉性囓齒目動物之腸道菌相研究

食葉性飛鼠是體型最小的樹棲哺乳動物，其體型為食葉性動物最小極限，全世界約有40種體型各異之飛鼠，彼此的基礎代謝率也因而有所差異，使得其各自占有食性利基。為了維持較高之單位質量代謝率，我們認為飛鼠的腸道菌扮演了關鍵的角色。本研究分析6隻Petaurista (平均體重1500 公克)、4隻Trogopterus (平均體重400 公克)、19隻Pteromys (平均體重150公克) 的腸道菌組成及預測其基因功能，利用次世代定序技術分析飛鼠糞便中16S核醣體核醣核酸基因並以PICRUSt演算法預測其分解纖維素之功能基因。結果顯示Petaurista 的腸道菌有95%屬於Firmicutes，Trogopterus約有83%屬於Firmicutes，而Pteromys則只有80%屬於Firmicutes。近年來的研究顯示肥胖的宿主其腸道中Firmicutes 占有比例均較高，且嚴格食葉性的哺乳動物體型極限大約為0.9-1.7公斤，因此得以推斷Petaurista 因為腸道中含有高比例之Firmicutes 而得以維持其高比例之食葉性，而Pteromys則依賴較多樣化之食物來源以維持其較高之單位質量代謝率。本研究亦以腸道菌之醣類代謝基因與代謝途徑、物種棲地之氣候來解釋宿主種間與宿主個體間之腸道菌相差異。

關鍵字

食葉性囓齒目動物；單位質量代謝率；腸道菌相；總體基因體學；次世代定序

並列摘要

Folivorous flying squirrels are among the smallest arboreal mammals, reaching the limit of metabolic demands subsisting on a low quality diet (e.g. leaves) that the flying squirrels recruit suites of gut microbes to digest throughout their evolution history. Yet, even among flying squirrel species (ca. 40 species), their body sizes differ by several folds posting drastic difference in mass-specific metabolic rates and dietary niche. Therefore we studied flying squirrels of three genera, Petaurista (average weight 1500 g), Trogopterus (average weight 400g) and Pteromys (average weight 150g) and expect to see different gut microbiota that may link to efficiency in digesting plant fibers. We analyzed the fecal samples from 6 Petaurista and 19 Pteromys with 16S rRNA gene amplicon and NGS. 160 and 510 OTUs were discovered in Petaurista and Pteromys, respectively. Gut microbiota are distinct in two genera. The most distinct feature of the differences lies in the bacterial phylum Firmicutes which are over 95% in Petaurista and only 80% in Pteromys. Firmicutes are considered more abundant in obese mice to gain higher mass-specific metabolic rates. It is generally considered that mammals below the mass range 0.9-1.7 kg are near the lowest mass margin a species can be strictly folivorous. Petaurista is strictly folivorous while Pteromys take more rich food such as fruits and nuts. Therefore, it appears that the strictly folivorous Petaurista might have recruited more Firmicutes to sustain primarily on leave. We also discuss the metabolic features in the bacterial phyla and weather of habitats that may contribute to the mass-specific metabolic rates and dietary niche of the two genera of flying squirrels.

並列關鍵字

folivorous rodent ； mass-specific metabolic rate ； gut microbiota ； metagenomics ； next generation sequencing

參考文獻

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國際替代計量

食葉性囓齒目動物之腸道菌相研究

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