Automated anaerobic cultivation and phenotyping of diverse chain-elongating bacteria

Decreasing the acetate-to-electron-donor ratio in diverse chain-elongating bacteria consistently shifts product distributions toward longer-chain carboxylates, though maximum chain length remains strain dependent.

• Why it matters: Conventional anaerobic cultivation is too low throughput to map physiology across many chain-elongating bacteria and electron donors, limiting understanding of how product specificity and tolerance arise.
• What they did: Using PACMAN, the study screened nine chain-elongating bacteria with 20 electron donors, compared observed substrate use to genome-derived pathways, and tested product profiles across acetate-to-electron-donor ratios and carboxylate concentrations.
• The result: The ratio shift reveals a general organizing principle for chain-length specificity, while carboxylate tolerance varies substantially; Gram-positive MCCA producers showed greater resilience than Gram-negative and butyrate-producing bacteria.

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