Table 2.

Effects of potential competitive inhibitors, inhibitors of energy generation, and thiol-containing enzymes on short-term uptake of [14C]choline in an estuarine filtrate culturea

Inhibitor Percent uptake in controlb
Competitive inhibitorsc
 Control (no addition)100 ± 4
 Glucose102 ± 2
 Ethanolamine91 ± 4
l-Proline82 ± 6
 Glycine79 ± 7
l-Proline75 ± 4
 Dimethylglycine68 ± 3
 Proline betaine54 ± 4
 Carnitine50 ± 1
 GBT trial 141 ± 2
 DMSP trial 140 ± 2
 DMSP trial 236 ± 1
 GBT trial 236 ± 1
 Choline trial 114 ± 1
 Choline trial 210 ± 1
Energy uncouplers or thiol-binding reagentsd
 DNP71 ± 3
 Sodium azide72 ± 3
p-CMB4 ± 3
  • a Filtrate culture was generated by filtering water through a GF/F filter by gravity. The culture, containing mainly free-living bacteria, was preincubated for 24 h in the dark prior to choline uptake assays.

  • b Values represent the means of duplicate determinations of total uptake of [14C]choline into filterable material, expressed as a percentage of the controls. The error terms indicate the range about the mean. The total uptake in controls ranged from 640 to 702 dpm · 10 ml of sample−1 depending on the trial. Incubation was carried out for 20 min.

  • c Competitive inhibitors were added at 200 nM immediately before the addition of 9.4 nM [14C]choline.

  • d 2,4DNP, azide, and p-CMB were added at 100 μM 1 h before the addition of 9.4 nM [14C]choline.