Fig. S1. Net benefit of phototrophy to AAP and PRP bacteria in a coastal ocean as a function of PAR. Net benefit is the difference between energy yields and construction costs. (A) High PSU values per cell, (B) Middle PSU and (C) Low PSU. High, middle and low refer to the assumed number of PSUs per cell, taken from the range of observed PSU numbers. For AAP bacteria: high = 3000, middle = 1700 and low = 600 (Table 3). For PRP bacteria: high = 24 000, middle = 10 000 and low = 3400 (Table 2). Energetic yield was calculated by assuming either a linear (solid lines labelled simply AAP or PRP) or a hyperbolic response to light intensity (‘AAP hyper’ and ‘PRP hyper’).


Fig. S2. Effect of growth rate on the net benefits of phototrophy for PRP bacteria with 10 000 PR molecules. A slower growth rate means that construction costs are spread out over more time, resulting in a greater net benefit. The horizontal dashed lines are estimates of maintenance energy.


Table S1. Some estimates of maintenance energy for aerobic heterotrophic bacteria. See also Tijhuis and colleagues (1993). The estimates are per milligram dry weight.

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