Today AEM released Expanding the Diversity of Bacterioplankton Isolates and Modeling Isolation Efficacy with Large-Scale Dilution-to-Extinction Cultivation, the final paper from Mike’s dissertation that details the three year DTE study he conducted. This effort was intense- 17 DTE experiments totaling 7,820 inoculated wells- and yielded excellent results, with 328 isolates and roughly 5% of the observed bacterioplankton community brought into culture. Quoting from the paper, “A large fraction of our isolates (43% of cultured OTUs and 30% of cultured ASVs) represented taxa present at median relative abundances‚ÄČof >0.1%, with 15% and 4% of cultured OTUs and ASVs, respectively, at median abundances‚ÄČof >1%.” Many of these are first of their kind isolates, like SAR11 LD12 or Actinobacteria acIV, or geographically novel versions of other previous cultured abundant taxa like SAR11 IIIa, SAR116, and HIMB59 Alphaproteobacteria, and OM43 and MWH-UniPo Betaproteobacteria.

Importantly, our colleague Ben Temperton developed a new model to improve upon Don Button’s whole-community viability estimates by combining DTE culturing results with relative abundance data to estimate per-taxon microbial viability in nature. This yielded some eye-popping results, such as the possibility that SAR11 taxa like LD12 and subclade IIIa may have maximum cellular viabilities in nature as low as 15%, meaning that large fractions of these organisms may occupy dormant states at any given time. This has critical implications for their roles in biogeochemical cycling. Nicole’s project is currently investigating this very phenomenon in extreme detail.