Fig. 1. Growth parameters for Alteromonas macleodii and Ruegeria pomeroyi grown in replete minimal media and minimal media without a vitamin B₁₂ source across a range of temperature treatments.

A Growth curves for both species from experimental trial 2. Colors represent temperature treatments, with the exact temperature for each treatment included in the legend. Point and line shapes represent the media treatment: replete (replete minimal media; circles and solid lines) and –B₁₂ (minimal media without vitamin –B₁₂; triangles and dashed lines). Each point is the mean log cell concentration of three biological replicates determined by flow cytometry, with error bars representing one standard deviation of the mean. Black vertical lines indicated by arrowheads designate time points where R. pomeroyi cultures were harvested for B₁₂ measurements by mass spectrometry. B Maximum cell concentrations (biomass) reached by A. macleodii in experimental trials 1 and 2. Horizontal marks represent the mean cell concentration for each treatment; vertical error bars are one standard deviation of the mean; open circles are individual data points. The statistical significance of media treatment at each temperature was tested by t-test and p < 0.05 is indicated on the plots by an asterisk (‘*’). There was a statistically significant reduction in maximum biomass by 57% and 22% in trials 1 and 2, respectively, when A. macleodii was grown without vitamin B₁₂ at the hottest temperature tested. C Maximum growth rates (µ_max) for A. macleodii and R. pomeroyi in each temperature and media treatment combination in experimental trial 2. Growth rates were calculated from individual growth curves using the ‘growthrates’ package in the R computing environment. The statistical significance of media treatment on mean maximum growth rate at each temperature was tested by t-test and p < 0.05 is indicated on the plots by an asterisk (‘*’). A. macleodii cultures grown in replete media had a significantly higher maximum growth rate at all temperatures but the difference in mean maximum growth rate (µ_max) between media treatments was largest in the hot temperature treatment (0.32 (27%), compared to 0.14 (14%) in mid and 0.13 (18%) in cool). The impact of media treatment on maximum growth rate was more varied for R. pomeroyi with the maximum growth rate significantly higher in replete media only at the highest temperature treatment.