圖片來源:Science Source/SPL
從巴西遺骸中發現的古代 DNA 顯示,蒼白密螺旋體疾病的起源比之前認為的要早約 10,000 年。
埃文.卡拉威 / 2024 年 1 月 24 日 / 新聞 / 自然
螺旋形細菌蒼白密螺旋體(人工著色)不僅會引起性梅毒,還會引起雅司病和貝耶爾病等傳染病。
近 2000 年前生活在南美洲東海岸的人們的遺骸提供了已知最古老的證據,證明了引起梅毒的微生物家族。
今天《自然》雜誌報導的這項發現,讓人們對克里斯多福哥倫布的船員向歐洲輸出梅毒這個本已搖搖欲墜的想法產生了進一步的懷疑。科學家表示,更重要的是,古代基因組將導致梅毒和其他「密螺旋體」疾病的蒼白密螺旋體的起源推回了數千年前。
一個破壞性的家庭
最臭名昭著的密螺旋體感染是性病梅毒,通常由梅毒螺旋體亞種引起,但也可由其他亞種引起。第二種亞種最常與雅司病 (yaws) 有關,雅司病會導致手腳皮膚損傷。第三種原因導致大多數口腔感染(稱為貝傑爾病,bejel)。如果不及時治療,這三種疾病都會損害骨骼。
梅毒和其他密螺旋體疾病的起源仍然是個謎。十五世紀末開始,梅毒在歐洲爆發,由此產生了哥倫布的船員從美洲引進這種疾病的理論。
但由於缺乏明確證據證明來自美洲的前哥倫布時期遺骸中存在梅毒,這引發了人們對這一理論的質疑。 2020 年,研究人員報告稱,在 15 世紀的歐洲發現了多種蒼白密螺旋體菌株,其中一些菌株的年代可能早於哥倫布船員的回歸。這項發現顯示,在航海者返回之前,這種細菌已經在歐洲進化了相當長的一段時間。
哥倫布之前
為了更了解美洲密螺旋體疾病的歷史,領導這項2020 年研究的瑞士蘇黎世大學考古遺傳學家Verena Schuenemann 和Kerttu Majander 及其同事在巴西南部海岸在埋藏約2000年前幾具人類遺骸的骨骼標本中尋找密螺旋體細菌的跡象。
導緻密螺旋體疾病的細菌基因組是從巴西一個巨大的貝丘下發現的有限數量的史前遺跡(黃色,人工著色)中恢復的。 圖片來源:何塞·菲利皮尼
研究人員發現,從骨頭中回收的蒼白密螺旋體基因組與通常引起貝耶爾病的現代亞種的基因組最相似,貝耶爾病是一種當今美洲不常見的疾病。古代基因組與通常與雅司病或梅毒相關的菌株的基因組不太相似,這兩種菌株都發現於南美洲。這意味著目前蒼白密螺旋體亞種的分佈與過去不同。
對基因組的進一步分析顯示,已知的蒼白密螺旋體譜係可能早在 14,000 年前就開始多樣化——比之前認為的早 10,000 年——而現代菌株是在過去 3,000 年進化而來的。「他們似乎已經陪伴我們很久了,這出乎我們的意料,」舒內曼說。
尋找密螺旋體的起源
西雅圖華盛頓大學的微生物學家希拉·盧克哈特(Sheila Lukehart) 表示,具有2000 年歷史的蒼白密螺旋體基因組「非同尋常」,這意味著三個關鍵亞種現已在美洲古代遺跡中全部被發現。
然而,人們越來越認識到密螺旋體亞種可以透過多種方式表現出來,盧克哈特補充道。例如,已知與貝耶爾病和雅司病相關的亞種會引起性病梅毒。因此,她說,「尋找梅毒的起源其實就是尋找密螺旋體的起源」。
研究人員表示,2000 年前在巴西發現了導致貝耶爾的密螺旋體,但這並不能直接反駁梅毒隨哥倫布回歸的觀點。但先前關於 15 世紀歐洲存在多種密螺旋體菌株的證據以及修改後的蒼白密螺旋體進化時間表使得這種可能性變得更加不可能。「所有這些都顯示它們不是從美洲進口的,」舒內曼說。
一種可能性是,密螺旋體疾病在歐亞大陸或非洲出現得更早,並且至少在 15,000 年前隨著第一批人類遷徙到美洲而到達美洲。
坦佩市亞利桑那州立大學的考古遺傳學家安妮·斯通(Anne Stone)並沒有參與這項研究,她說,另一個原因是細菌從動物宿主轉移到人類身上。她指出,靈長類和其他動物,包括兔子,都可能感染梅毒螺旋體。「可能有我們必須考慮的儲藏窩」。
doi:https://doi.org/10.1038/d41586-024-00191-9
參考文獻:
1. Majander, K. et al. 《 自然》, https://doi.org/10.1038/s41586-023-06965-x (2024)。
- Harper, K.N.、Zuckerman, M.K.、Harper, M.L.、Kingston, J.D. & Armelagos, G.J. 《美國體質人類學雜誌》, 146, 99–133 (2011)。
- Majander, K. et al. 《當代生物學》, 30, 3788–3803 (2020)。
The spiral-shaped bacterium Treponema pallidum (artificially coloured) causes not only venereal syphilis but also the infectious diseases yaws and bejel.Credit: Science Source/SPL
Remains of people who lived on the eastern coast of South America nearly 2,000 years ago have yielded the oldest known evidence for the family of microorganisms that cause syphilis.
The discovery, reported today in Nature, casts further doubt on the already shaky idea that Christopher Columbus’s crew exported syphilis to Europe. More importantly, say scientists, the ancient genomes push back the origins of Treponema pallidum, which causes syphilis and other ‘treponemal’ diseases, by thousands of years.
A destructive family
The most notorious treponemal infection is venereal syphilis, which is generally caused by the subspecies T. pallidum pallidum but can be caused by other ones as well. A second subspecies is most commonly linked to yaws, which cause skin lesions on the hands and feet. And a third causes most cases of an oral infection known asbejel . Left untreated, all three diseases can damage the bones.
The origins of syphilis and the other treponemal diseases remain a mystery. Explosive syphilis outbreaks in Europe starting during the late fifteenth century led to the theory that Columbus’s crew imported the disease from the Americas.
But the lack of clear evidence for syphilis in pre-Columbian remains from the Americas raised questions about this theory. In 2020, researchers reported the discovery of diverse T. pallidum strains in fifteenth century Europe — some of them potentially pre-dating the return of Columbus’s crew. The find suggested that the bacterium had already evolved in Europe for a considerable amount of time before the voyagers’ return.
Before Columbus
To better understand the history of treponemal disease in the Americas, Verena Schuenemann and Kerttu Majander, archaeogeneticists at the University of Zurich in Switzerland who led the 2020 study, and their colleagues looked for signs of treponemal bacteria in bone specimens of human remains buried some 2,000 years ago on Brazil’s southern coast.
Syphilis microbe’s family has plagued humans for millennia
Ancient DNA recovered from Brazilian remains shows that treponemal diseases originated some 10,000 years earlier than previously thought.
Ewen Callaway / 24 January 2024 / NEWS / Nature
Genomes of bacteria that cause treponemal disease were recovered from a limited number of prehistoric remains (yellow, artificially coloured) found beneath an enormous shell mound in Brazil.
Credit: Jose Filippini
The researchers found that the T. pallidum genomes recovered from the bones were most similar to those of the modern subspecies that usually causes bejel — a disease that is not typically found in the Americas today. The ancient genomes were less similar to those of the strains usually associated with yaws or syphilis, which are both found in South America. This implies that the current distribution of T. pallidum subspecies differs from that of the past.
Further analysis of the genomes suggested that known T. pallidum lineages probably began to diversify as long as 14,000 years ago — 10,000 years earlier than previously suggested — and that modern strains evolved in the past 3,000. “It seems they have been accompanying us for a long time, which wasn’t expected,” says Schuenemann.
Searching for Treponema’s origins
The 2,000-year-old T. pallidum genomes are “remarkable”, says Sheila Lukehart, a microbiologist at the University of Washington in Seattle, and mean that the three key subspecies have now all been identified in ancient remains in the Americas.
However, there is growing recognition that the treponemal subspecies can manifest themselves in several ways, Lukehart adds. For instance, bejel- and yaws-linked subspecies have been known to cause venereal syphilis. As a result, she says, “the search for the origin of syphilis is really a search for the origin of the Treponema”.
The discovery of bejel-causing Treponema in Brazil 2,000 years ago doesn’t directly disprove the idea that syphilis came back with Columbus, the researchers say. But the previous evidence for diverse Treponema strains in fifteenth century Europe and the revised evolutionary timescale for T. pallidum makes it even more unlikely. “All this points in the direction that they are not being imported from the Americas,” says Sch