肠道菌群可随季节变化而改变
2017年8月25日，美国科学促进会《科学》封面发表美国斯坦福大学、德克萨斯人类食物工程、圣迭戈加利福尼亚大学、纽约大学、英国伦敦大学国王学院、圣托马斯医院、加拿大西安大略大学、坦桑尼亚国家医学研究所的研究报告，发现坦桑尼亚狩猎采集者的肠道菌群组成会随着他们食物的季节变化而改变，他们肠道微生物组的成分也与那些吃西方饮食者大相径庭。
哈扎人是非洲剩下的以狩猎采集方式生活的最后一批人，坚持这种传统生活方式的人已经不到200人。他们的饮食因季节而异：在潮湿的雨节，他们会更经常地觅食浆果和吃蜂蜜；他们在干旱季节的狩猎则最为成功。为更好地了解饮食与微生物组之间的关系模式，该研究在不同季节收集了来自188个哈扎人的350个粪便样本及饮食数据。
结果发现，在干旱季节结束至潮湿季节开始之间的这段时间，他们粪便中70%的拟杆菌类消失了，但是这些细菌主体会在较后时间点重新出现。在哈扎人的粪便中总共发现了4个科的细菌尤其会随季节而改变。接着，该研究将哈扎人的肠道微生物组与16个国家18个人群的微生物组进行了比较，工业化地区人群的肠道微生物组由拟杆菌占主导，在微生物组中的平均比例达21%，而该比例在吃传统食物人群中为0.8%；同样，在哈扎人和其他进食传统食物人群中的2种普遍存在的细菌，在进食非传统食物的人群中罕见或完全无法检测到。哈扎人还比进食西方饮食的人有更多的用于加工植物碳水化合物的酶。美国人群的肠道菌群要比哈扎人的菌群展现出大幅增多的对抗生素有抵抗力的基因。
因此，随着寒来暑往、秋收冬藏，不同季节饮食结构的变化可导致肠道菌群功能的相应变化，进而影响到肠道菌群组成。
对此，美国国家环境卫生科学研究所发表同期评论：肠道的季节变化。
Science. 2017 Aug 25;357(6353):802-806.
Seasonal cycling in the gut microbiome of the Hadza hunter-gatherers of Tanzania.
Samuel A. Smits1, Jeff Leach, Erica D. Sonnenburg, Carlos G. Gonzalez, Joshua S. Lichtman, Gregor Reid, Rob Knight, Alphaxard Manjurano, John Changalucha, Joshua E. Elias, Maria Gloria Dominguez-Bello, Justin L. Sonnenburg.
Stanford University, Stanford, CA, USA; Human Food Project, Terlingua, TX, USA; King's College London, St. Thomas' Hospital, London, UK; Western University, London, Ontario, Canada; University of California, San Diego, CA, USA; National Institute for Medical Research, Mwanza, Tanzania; New York University, New York, NY, USA.
Seasonal diets, seasonal microbiota
Among the Hadza of western Tanzania, a few hundred people still live in small groups as hunter-gatherers, reliant solely on the wild environment for food. Smits et al. found that the microbiota of these people reflects the seasonal availability of different types of food (see the Perspective by Peddada). Between seasons, striking differences were observed in their gut microbial communities, with some taxa apparently disappearing, only to reappear when the seasons turned. Further comparison of the Hadza microbiota with that of diverse urbanized peoples revealed distinctly different patterns of microbial community composition.
Although humans have cospeciated with their gut-resident microbes, it is difficult to infer features of our ancestral microbiome. Here, we examine the microbiome profile of 350 stool samples collected longitudinally for more than a year from the Hadza hunter-gatherers of Tanzania. The data reveal annual cyclic reconfiguration of the microbiome, in which some taxa become undetectable only to reappear in a subsequent season. Comparison of the Hadza data set with data collected from 18 populations in 16 countries with varying lifestyles reveals that gut community membership corresponds to modernization: Notably, the taxa within the Hadza that are the most seasonally volatile similarly differentiate industrialized and traditional populations. These data indicate that some dynamic lineages of microbes have decreased in prevalence and abundance in modernized populations.
DOI: 10.1126/science.aan4834
Science. 2017 Aug 25;357(6353):754-755.
Seasonal change in the gut: The gut microbiome of Hadza hunter-gatherers changes with the season.
Shyamal Peddada.
National Institute of Environmental Health Sciences, Durham, N, USA.
We live in a dynamic environment where diet, weather, social interactions, lifestyles, and a host of other factors change on a regular basis. Consequently, the microbial composition of even a healthy person's gut is subject to natural variations; however, not much is known about these variations. On page 802 of this issue, Smits et al. study seasonal changes in the gut microbiome of the Hadza population (see the photo), a hunter-gatherer community residing near Lake Eyasi in Tanzania, Africa, during the wet and dry seasons of 2013 and 2014. Using a new methodology, they identify operational taxonomic units (OTUs)—clusters of reads that are a proxy for taxons—that respond to seasonal changes in diet, activity, and the external environment, thereby maintaining a healthy gut.
DOI: 10.1126/science.aao2997