Microbial CO₂ respiration rates (gray line) and cell densities (squares and circles) measured during replicate coculture incubations of Vibrio splendidus 1A01 and Pseudoalteromonas sp. 3D05 with (A) glucosamine; (B) unimpacted Guaymas Basin sediment; and (C) hydrothermal Guaymas Basin sediment. Error bars represent the standard error between dPCR measurements from replicate subsamples.