Quantifying microbial fitness in high-throughput experiments.

Different high-throughput mutant fitness statistics in Saccharomyces cerevisiae and Escherichia coli can yield significantly different fitness interpretations, including altered effect sizes, epistasis signals, and mutant rankings.

• Why it matters: Fitness is central to evolution, yet high-throughput measurements use inconsistent definitions, making results hard to compare and potentially misleading for evolutionary dynamics and gene-function inference.
• What they did: The authors systematize fitness statistics by three choices—relative-abundance encoding, the measurement time scale, and the reference subpopulation in bulk DNA-barcoded competitions—and analyze how these choices change inferred fitness.
• The result: These definition differences are linked to significantly different mutant fitness interpretations in both microbes, implying that consistent fitness definitions are necessary for reproducible, comparable results across experiments.

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