進入微生物組領域也這麼久了，每天閱讀的文獻，總會碰到microbiota, metagenome, microbiome這三個關鍵字，估計很多朋友不太清楚它們的具體意思什麼。
首先從Wiki學習，這裡還是非常專業的。
Microbiota 微生物群微生物群是指研究動植物體上共生或病理的微生物生態群體。微生物群包括細菌、古菌、原生動物、真菌和病毒。研究表明其在宿主的免疫、代謝和激素等方面非常重要。近義詞Microbiome微生物組既包括微生物，又包括其基因組。
附Wiki原文
A microbiota is an 「ecological community of commensal, symbiotic and pathogenic microorganisms」 found in and on all multicellular organisms studied to date from plants to animals. A microbiota includes bacteria, archaea, protists, fungi and viruses. Microbiota have been found to be crucial for immunologic, hormonal and metabolic homeostasis of their host. The synonymous term microbiome describes either the collective genomes of the microorganisms that reside in an environmental niche or the microorganisms themselves.
The microbiome and host emerged during evolution as a synergistic unit from epigenetics and genomic characteristics, sometimes collectively referred to as a holobiont.
宏基因是指直接研究環境樣品作為遺傳學材料。廣義來説其包括環境基因組、生態基因組學和群體基因組學。傳統的微生物學和微生物基因測序依賴於單克隆的培養，早期環境基因測序克隆16s rRNA基因等特定基因來確定自然樣品中的生物多樣性。此方法將會漏掉大量末被培養的微生物多樣性。最近研究採用鳥槍法或PCR直接測序方法來獲得樣品群體中所有成員無偏好的基因。因為這類方法可以展現從前無法發現的微生物多樣性，因此宏基因組方法提供了革命性的工具去理解我們整個生活的世界。隨著測序價格的下降，宏基因組允許微生物生態研究比之前更大的尺度和更多細節。
Metagenomics is the study of genetic material recovered directly from environmental samples. The broad field may also be referred to as environmental genomics, ecogenomics or community genomics. While traditional microbiology and microbial genome sequencing and genomics rely upon cultivated clonal cultures, early environmental gene sequencing cloned specific genes (often the 16S rRNA gene) to produce a profile of diversity in a natural sample. Such work revealed that the vast majority of microbial biodiversity had been missed by cultivation-based methods. Recent studies use either 「shotgun」 or PCR directed sequencing to get largely unbiased samples of all genes from all the members of the sampled communities. Because of its ability to reveal the previously hidden diversity of microscopic life, metagenomics offers a powerful lens for viewing the microbial world that has the potential to revolutionize understanding of the entire living world. As the price of DNA sequencing continues to fall, metagenomics now allows microbial ecology to be investigated at a much greater scale and detail than before.
Microbiome 微生物組WiKi認為其與Microbiota同義，均為Microbiota詞條。但其實這兩個詞區別還是很有的，看下圖。
下面這篇Nature的Review，用圖形的方法對這三個詞進行了定義和描述，讓我們來學習一下：
圖1. 本綜述中對微生物群、宏基因組和微生物組的定義。
每張圖代表的是相同的群體，然而不同的方法可以定義此群體可提供的不同信息。
a. 微生物群：採用16S rRNA研究方法鑑定此環境中微生物的種類。
b. 宏基因組：微生物群的基因和基因組，包括質粒、強調群體的遺傳學潛能。
c. 微生物組：微生物群的基因和基因組，以及微生物群的產物與宿主環境。
英文原始圖注Figure 1: Definition of the microbiota, metagenome and microbiome as used in this Review.
Each image represents the same population; however, different approaches to define the population provide different information.
a | Microbiota: 16S rRNA surveys are used to taxonomically identify the microorganisms in the environment.
b | Metagenome: the genes and genomes of the microbiota, including plasmids, highlighting the genetic potential of the population.
c | Microbiome: the genes and genomes of the microbiota, as well as the products of the microbiota and the host environment.
Abbreviation: rRNA, ribosomal RNA.
Figure 1: Definition of the microbiota, metagenome and microbiome as used in this Review. http://www.nature.com/nrurol/journal/v12/n2/fig_tab/nrurol.2014.361_F1.html
The microbiome of the urinary tract—a role beyond infection http://www.nature.com/nrurol/journal/v12/n2/full/nrurol.2014.361.html
【明概念】微生物組（microbiome）http://www.biotrainee.com/thread-156-1-1.html
http://www.microbe.net/2015/04/08/what-does-the-term-microbiome-mean-and-where-did-it-come-from-a-bit-of-a-surprise/
https://en.wikipedia.org/wiki/Microbiota
https://en.wikipedia.org/wiki/Metagenomics
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