Bacterial utilization of algal extracellular products. 3. The specificity of algal‐bacterial interaction

Kinetic analyses were made of the utilization of 14 C‐labeled algal extracellular products (EP) by bacterial populations in continuous algal cultures containing steady state Skeletonema costatum or Dunaliella tertiolecta. The development of bacteria adapted to the respective algal species was revealed by gradual evolution of a common X‐intercept for net EP uptake and respiration lines from initially disparate estimates. When the adapted populations were given labeled EP prepared from other algal species, linear kinetics were retained but the X‐intercepts for net uptake and respiration failed to coincide. Bacterial response to a given algal EP pool does not necessarily preclude enzyme‐mediated utilization of organic substrates from other species. Rapid utilization of algal EP appears to be a consequence of bacterial adaptation to existence under dilute nutrient conditions rather than a response to a specific alga. Prolonged exposure to a single alga may favor the development of bacterial populations in which metabolism is limited by enzyme‐mediated transport of the compounds available in its EP pool, but this phenomenon is less significant ecologically than the general stimulation of bacterial activity effected by the increased supply of these compounds.