Carbon Nutrition and Metabolism of Polytomella caeca*

SYNOPSIS. Polytomella caeca utilizes as sole carbon sources in chemically defined media: acetate, propionate, butyrate, valerate, pyruvate, succinate, ethyl, butyl, amyl, and hexyl alcohols. Glyceraldehyde and α‐ketoglutarate sustain very small populations. Caproate, caprylate, fumarate, malate, propyl, heptyl, and octyl alcohols and the iso‐compounds iso‐butyrate, iso‐butyl and iso‐hexyl alcohols are inadequate. Acetate is not assimilated ‐1. pH after growth of fatty acid media is 8.4 ± 0.4; stable in pH 2.0 pyruvate and pH 3.0 succinate media; 3.5 ± 0.3 in alcohol media with initial pH <6.0. Longer alcohols cause less pH decrease during growth. Acetate concentrations <0.2% do not support maximum populations; concentrations of 0.2–1.0% do. pH after growth increases in these media to pH 8.5 with maximum populations. Malate, fumarate, α‐ketoglutarate, and lactate seem not to penetrate the cell, but are metabolized by homogenates. Methylene blue reduction by homogenates indicates the presence of lactic, malic, succinic and α‐ketoglutaric dehydrogenases, fumarase and glutamic transaminase. Extracts contain Embden‐Meyerhof phosphate esters, ATP, and ADP.