細菌と真菌が混在したマイクロバイオームの定量解析を可能に~人工核酸標準物質の開発で次世代シーケンサーによる解析の標準化に貢献~

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2025-03-18 産業技術総合研究所

産業技術総合研究所(産総研)は、次世代シーケンサーを用いたマイクロバイオーム解析のための12種類の人工核酸標準物質を開発しました。 これにより、細菌などの原核生物と真菌などの真核微生物の比較および絶対定量が可能となり、これまで困難だった真菌を含む詳細なマイクロバイオーム研究が進展すると期待されます。この技術は、疾患に関連するマイクロバイオーム情報と健康な状態との比較に有用であり、新たな診断薬や治療薬の開発に寄与する可能性があります。

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rRNA遺伝子アンプリコンシーケンスによるマイクロバイオームのクロスドメイン絶対定量化のための合成DNAスパイクイン標準物質 Synthetic DNA spike-in standards for cross-domain absolute quantification of microbiomes by rRNA gene amplicon sequencing

Dieter M Tourlousse, Yuji Sekiguchi
ISME Communications  Published:17 March 2025
DOI:https://doi.org/10.1093/ismeco/ycaf028

(A) Overview of the rDNA-mimics. The upper part of the schematic shows the organization of the fungal/eukaryotic rRNA operon along with the partial bacterial 16S rRNA gene (V4 hypervariable region) incorporated in two of the rDNA-mimics. The middle part shows the layout of the rDNA-mimics, consisting of artificial sequences flanked by conserved sequences of the natural rRNA genes of the yeasts S. cerevisiae (Sc) and C. neoformans (Cn). Colored squares on the right correspond to the legend in panel B. The lower part indicates the location of the PCR primers used for experimental evaluation of the rDNA-mimics. (B) Testing of the rDNA-mimics with an equimolar formulation of all 12 rDNA-mimics (mix E). Stacked bar charts of the relative abundances of the rDNA-mimics, averaged over three technical replicates, for amplicon libraries generated with the primer sets shown on the x-axis. (C) Testing of the rDNA-mimics with mix E added to an even fungal or bacterial mock community. Each symbol shows an individual data point from three technical replicates. Symbols for the rDNA-mimics are colored as in panel B and data for all species in the mock communities are shown as dark grey circles. (D) Scatter plot of species abundances for the fungal (mock F) or bacterial (mock B) mock community + mix E samples (y-axis) against the mock community-only samples (x-axis). Data are shown as the mean (circles) and SD (error bars) of three technical replicates, with fill colors indicating the primer set. The solid line represents the 1:1 diagonal and the corresponding R2 value is indicated.

Abstract

Microbiome studies using high-throughput sequencing are increasingly incorporating absolute quantitative approaches to overcome the inherent limitations of relative abundances. In this study, we have designed and experimentally validated a set of 12 unique synthetic rRNA operons, which we refer to as rDNA-mimics, to serve as spike-in standards for quantitative profiling of fungal/eukaryotic and bacterial microbiomes. The rDNA-mimics consist of conserved sequence regions from natural rRNA genes to act as binding sites for common universal PCR primers, and bioinformatically designed variable regions that allow their robust identification in any microbiome sample. All constructs cover multiple rRNA operon regions commonly targeted in fungal/eukaryotic microbiome studies (SSU-V9, ITS1, ITS2, and LSU-D1D2) and two of them also include an artificial segment of the bacterial 16S rRNA gene (SSU-V4) for cross-domain application. We validated the quantitative performance of the rDNA-mimics using defined mock communities and representative environmental samples. In particular, we show that rDNA-mimics added to extracted DNA or directly to the samples prior to DNA extraction precisely reflects the total amount of fungal and/or bacterial rRNA genes in the samples. We demonstrate that this allows accurate estimation of differences in microbial loads between samples, thereby confirming that the rDNA-mimics are suitable for absolute quantitative analyses of differential microbial abundances.

生物工学一般
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